We discuss how the most extreme δ34S values observed could be related to unique DMSP cycling in the seasonally extreme physiochemical conditions of isolated brine inclusions in winter-spring. Using cell cultures, we show that part of the DMSP δ34S variability could be explained by distinct DMSP metabolism in sea ice microalgae. These findings advance our understanding of the sea ice sulfur cycle and metabolic adaptations of microbes in extreme environments.Sea ice microbial communities produce large amounts of the sulfur metabolite dimethylsulfoniopropionate (DMSP), a precursor of the climate cooling gas dimethylsulfide. Despite their importance to the polar sulfur cycle, drivers and metabolic pathways of sea ice DMSP are uncertain. Here we report the first measurements of sea ice DMSP sulfur isotopic composition ( Gauthier Carnat et al. report the first measurements of the natural sulfur isotopic composition of sea ice from the Antarctic. They find considerable variability between seasons and sea ice horizons, suggesting unique cycling of sulfur metabolites by sea ice microalgae in extreme environments, with important implications for the production of gasses that impact global climate. Multiple physiological roles have been suggested for DMSP to aid in environmental stress adaptation including cryoprotection3, osmoregulation4, and protection against oxidative stress5. DMSP is also a major precursor of the most abundant volatile sulfur compound in oceanic waters, dimethylsulfide (DMS). Oceanic emissions of DMS represent about 25% of the global sulfur flux to the atmosphere6, where it is quickly oxidized to condensable acidic sulfur species7. As a precursor of sunlight-scattering sulfate aerosols and cloud-condensation nuclei, DMS could play a role in climate warming mitigation, although the level of its contribution is still debated9.Dimethylsulfoniopropionate (DMSP) is an important sulfur metabolite synthesized by marine microalgae10. DMS emissions in these regions are strongly influenced by the development of seasonal sea ice. Liquid salty micro-inclusions (brine), which remain trapped between sea ice crystals on freezing, provide a habitat for metabolically active microbial communities (sympagic communities) which can support very high biomass11. These communities are known to periodically produce DMS and DMSP concentrations that are several orders of magnitude greater than global oceanic means13, and release of these sulfur and microbial pools at the ice edge during the spring–summer melt season have been correlated to strong DMS pulses and atmospheric aerosols formation events14.DMS climate-cooling potential may prove to be particularly relevant in the climate-sensitive and aerosol-poor polar regions13 which is currently not well predicted by models. Some of this variability has been correlated with the seasonal evolution of sympagic algal biomass and its vertical zonation in taxonomically distinct assemblages17, DMSP production being known to differ strongly among taxonomic groups18. Sympagic microbial communities also thrive in seasonally and vertically variable physiochemical conditions, mainly driven by changes in sea ice thermodynamics and brine dynamics19. For instance, sympagic microbes must cope with salinities ranging from < 10 g kg−1 in summer melt channels to over 200 g kg−1 in isolated winter brine pockets, and with temperatures ranging from −20 °C in winter surface ice to −1.8 °C at the ice–ocean interface11. High variability in oxygen levels, nutrient supply, light availability, and pH between the different sea ice habitats have also been reported20. As suggested by many22, such variability in physiochemical conditions should strongly influence microbial processes driving the production and degradation of DMS and DMSP1. Unfortunately, only the influence of brine salinity and temperature on microalgal cell physiology and DMSP synthesis was investigated in some details23. Moreover, the exact contribution of sea ice DMS to the annual oceanic DMS flux to the atmosphere remains extremely difficult to quantify. Sea ice may transfer DMS to the polar ocean and ultimately to the atmosphere via multiple pathways such as brine drainage at the ice edge during the entire season24 and melting and ice-breakup in summer14. Direct emissions of DMS from the ice surface and leads have also been observed25.Despite its potential importance for the sulfur cycle in the polar ocean and atmosphere, the biogeochemical cycling of sea ice DMS and DMSP is still poorly understood. Field measurements of sea ice DMS and DMSP concentrations show considerable spatial and temporal variability26. A sensitive method for δ34S analysis in DMS and DMSP in seawater samples was developed in 2013, coupling gas chromatography (GC) and multicollector inductively coupled plasma mass spectrometry (MC-ICPMS)27. Using this method, Amrani et al.28 analysed surface water DMSP samples from six different ocean provinces, revealing a remarkable consistency in δ34S values. Other studies in non-oceanic aquatic environments with different physiochemical conditions such as salt marshes28 and freshwater lakes29 reported very different isotopic values. Until now, the natural sulfur isotopic composition  of DMSP had never been measured in the highly variable sea ice environment.Natural isotopes measurement is a powerful approach to trace sources and transformation processes in complex biogeochemical cycles34S variability in Antarctic sea ice. Considerable variability is revealed across seasons and between sea ice horizons, with multiple values falling out of the range observed in oceanic waters. We show that the highest variability and most extreme DMSP δ34S values are generally found in cold and highly saline isolated brine pockets, while the isotopic signatures in warmer and fresher connected brine channels are more homogeneous. We discuss how the variability could relate to brine inclusions connectivity and its effect on mixing, and to the cycling of DMSP by bacteria and heterotrophs in the isolated brine pockets. Using cell cultures of the polar diatom Fragilariopsis cylindrus in brine conditions, we show that part of the variability could originate from distinct DMSP metabolism in sea ice algae.In this study, we present the first assessment of DMSP δ34S values in sea ice was assessed from a set of Antarctic sea ice cores collected in two different regions of the Southern Ocean , and at four different stations in the central Ross Sea and Ross Sea marginal ice zone (PIPERS field study31). One land-fast ice station was visited seven times during a year-round time series study in the McMurdo Sound, Ross Sea (YROSIAE field study13). At each station, DMSP δ34S were determined as a function of depth, targeting distinct sea ice horizons  and their associated microalgal assemblages.The variability of DMSP δ34S showed very high variability, with values ranging between +10.6 and +23.6‰ (n = 65)  waters)  δ34S values. Such light DMSP δ34S have been recorded in non-oceanic aquatic environments such as salt marshes (+11.3‰)28 and freshwater lakes (+11.4‰)29, where the source sulfate for DMSP metabolism was much lighter than seawater sulfate. Closer inspection of sea ice DMSP δ34S values reveals substantial variability between the three sets of ice cores collected  was also much lighter than in the two other sets. No correlation was found between DMSP δ34S and DMSP concentrations in any of the ice core sets  Fig. . To put rs) Fig. . The majted Fig. . Pack ic13. This set of ice cores was therefore selected to study the temporal/seasonal variability in sea ice DMSP δ34S, since the two other sets integrated spatial variability and were sampled over a much shorter time frame31. Temporal trends during the YROSIAE study are described here in four distinct sea ice horizons corresponding to distinct microalgal assemblages 13  as described in ref. 13. While the mean DMSP δ34S of each station were relatively similar , sharp contrasts could be observed between the shape and range of the depth profiles , and a strong vertical variability between the surface/interior ice horizons and bottom/ice–ocean interface horizons. This variability observed in <2 m of sea ice was higher than the overall variability observed in surface oceanic waters, and in 120 m depth seawater profiles from the Red Sea28. Interestingly, the late-winter core (YRS4) also had a heavy δ34S value in its interior ice horizon. On the other hand, the spring–summer transition cores showed more homogeneity. A trend of 34S depletion in surface ice compared to sub-surface ice was observed in all cores, and bottom/ice–ocean interface δ34S values were always very close to the typical oceanic waters range.The YROSIAE study in the McMurdo Sound provided an opportunity to sample the same fast-ice site from the winter–spring transition (mid-September) to the spring–summer transition (late-November), covering the full seasonal cycle (growth and decay) of a sympagic bloom)13 Fig. . Two conles Fig. . The win34S values sampled in six different ocean provinces encompass a wide range of hydrological, meteorological, and biological conditions32 , which fall within the range of near-surface oceanic waters signatures , taken up through assimilatory sulfate reduction34. The concentration of SO42− in sea ice is regulated by a complex interplay between the concentration/dilution of salts as sea ice forms/melts, the temperature-driven sequential precipitation/dissolution of sulfate minerals (gypsum and mirabilite), and brine exchanges with seawater in the case of an open permeable brine system37. As a result, the bioavailability of sulfate is much more variable in the brine habitat than in oceanic waters which show a stable concentration of 28 mM34. Evaluating the SO42− concentration and δ34S signature in our sea ice sample was therefore of specific interest. Sulfate concentrations were determined in bulk ice from the YROSIAE study and weighted by the brine volume fraction to estimate the amount of sulfate available in brine 39. Sulfur isotope measurements of bulk ice sulfate in the ice core set from the McMurdo Sound . These results are consistent with those reported in frost flowers and sea ice in the Canadian High Arctic, and support the assumption of no isotopic fractionation during mirabilite formation40.The S source for microalgal DMSP synthesis in oxygenated parts of the oceanic water column is widely accepted to be dissolved sulfate  and temperature (T) shifts typically encountered by these organisms in the brine habitat across seasons20. F. cylindrus is an ice-associated diatom widespread in both polar regions whose cell physiology and DMSP metabolism in sea ice physiochemical conditions have been studied in some details23. Temperature and salinity are known not only to control DMSP production in ice-associated algae23 but also to control the abundance and activity of enzymes involved in microalgal sulfate assimilation41 and DMSP synthesis42. F. cylindrus cultures were brought from cold oceanic conditions  to high salinity conditions , and to combined high salinity–low temperature conditions   was measured in both experiments  at the start of the experiment and after 48 h were relatively similar, averaging +3.1‰ ± 0.2‰ (n = 4). Considering that the source sulfate in the culture water  had a δ34S of +6.5‰ (± 0.1‰), the corresponding apparent fractionation factor from sulfate to DMSP was on average −3.4‰ ± 0.06‰ (n = 4)  after 24 h, 48 h, and 1 week were also relatively similar  but ±1‰ lighter than in the control culture, yielding an apparent fractionation factor of −4.3‰ ± 0.09‰ (n = 6) on average  were slightly more variable  and 1 week (+2.1‰) were comparable to those of the high salinity–low temperature culture, but heavier after 48 h (+2.9‰), yielding an apparent fractionation factor of −4.2‰ ± 0.4‰ on average (n = 6)  Fig. . This vaage Fig. . DMSP δ3 6) Fig. .Fig. 3Ch34S in all the ice core sets suggests that more than one process drive the isotopic signature of DMSP in sea ice. The results of the present study point toward an important role of sea ice thermodynamic growth and the vertical/seasonal development of the brine inclusions network. In particular, the stark contrast between small, cold, and highly saline isolated brine pockets that develop in cold ice, and larger, warmer, and fresher connected brine channels that develop in warmer ice warrants further consideration  than in cultures in cold oceanic conditions (−3.4‰). The exact mechanism driving this difference in fractionation remains uncertain. Enzymatic biotransformation of assimilated sulfate to methionine followed by methionine transaminase are the common metabolic pathways of DMSP in most oceanic taxonomic groups46. Several steps in these pathways remain poorly understood42. Depending on physiochemical conditions, reactions in these pathways could be catalysed by different enzymes isoforms, with different kinetic properties and different cellular compartments localisations41. Looking at the proteome response to increased brine salinity in F. cylindrus, Lyon et al.23 suggested that degradation of light harvesting proteins could be an alternative source of methionine for DMSP synthesis. They also identified key enzymes that could catalyse the conversion of methionine to DMSP, enzymes that were not identified in oceanic diatoms42.Results of our controlled experiments with 34S observed in our sea ice samples  on the RV-Polarstern in June–August 2013. A general overview of the AWECS sampling strategy and area is given in ref. 30. Three pack ice stations of AWECS were analysed in this work . The last set of ice cores was collected during the PIPERS (Polynyas and Ice Production in the Ross Sea) study on the RV Nathaniel B. Palmer in the Ross Sea in April–June 2017. Two stations were visited in the marginal ice zone (PIP1 and 4), and two in the central Ross Sea ice pack (PIP29 and 23).Three sets of ice cores were collected for this work. The first set was sampled in the McMurdo Sound during the YROSIAE (Year Round Survey of Ocean-Sea Ice-Air Exchanges in Antarctica) time series study in 2011–2012. One fast ice station located at Cape Evans was sampled seven times throughout the seasons  as described in ref. 13 was followed during the three studies. Briefly, an electropolished stainless-steel (SS) ice corer with an internal diameter of 14 cm was used to retrieve ice cores. Cores were immediately wrapped in polyethylene (PE) bags and kept at <−30 °C horizontally in the dark to prevent brine drainage from the cores and limit the physiological activity of ice algae47. One core per sampling event was fully dedicated to all the S analysis . Two other cores  were used to determine ancillary parameters as described below. The distance between the three cores collected was always <20 cm to limit spatial variability.The same ice coring procedure48.Liquid samples (sea water and brine) were collected during the PIPERS study. Sea water was sampled at three different SOCCOM float locations in the Ross Sea sector of the Southern Ocean using a CTD-Rosette sampler (5 m depth). Liquid samples were transferred to pre-acidified no headspace glass vials for long-term conservation at 4 °C in the dark47. This technique was developed to prevent artificial conversion of DMSP to DMS on melting. One of the ice cuboids was inserted with two grade-316 SS marbles into an air-tight grade-316 SS container. The container was mechanically shaken by a fast up and down motion of the crushing device, reducing the cuboid into a fine ice powder by repeated impacts with the marbles. The ice powder resulting from the crushing step was retrieved and the DMSP content was then quantified as DMS after cold alkali cleavage of DMSP into DMS. The ice powder was left to melt at 4 °C overnight with NaOH pellets in several sealed sparging vials equipped with a Teflon septum. One vial was then connected to a traditional purge-and-trap apparatus, and DMSP quantified as DMS with an Agilent 7890A GC-dual FPD system (DB1-Sulfur Specific column)13. The system was calibrated with pure (>99%) DMS (Merck®) dilutions in Milli-Q water. Triplicate measurements of DMSP in ice samples gave relative standard deviations <12%.The S dedicated ice core was cut into 5 or 10 cm vertical sections. Several smaller ice cuboids were then cut in the centre part of these sections for the different S analysis. Ice cuboids for DMSP concentrations were cut and processed in the field within 48 h of sampling. DMS was first extracted from the ice matrix using the dry crushing technique47. Storage times were 4 years, 3 years, and 5 months for the YROSIAE, AWECS, and PIPERS ice cores sets, respectively. Total DMSP concentrations are usually well preserved after long-term storage in ice cores as shown by the storage tests (>2 years) of Stefels et al.47.Ice cuboids for sulfate concentrations and sulfur isotope measurements were cut in the S dedicated ice core sections in the home laboratory. Ice core sections were kept at all time wrapped in PE bags in the dark and at −30 °C between sampling and analysis. This storing procedure has been proven effective in limiting brine drainage from the samples and physiological activity of microalgae34S) and reported relative to the international reference standard Vienna Cañon Diablo Troilite (V-CDT) in units of permil (‰) following equation:34R is the integrated 34S/32S ion-current ratio of the sample and standard peaks. A sparging vial was connected to a purge-and-trap apparatus (see ref. 27 for a detailed description), and DMS resulting from the base-cleavage of DMSP subsequently transferred via a six-way valve  into a Trace GC  for separation to individual compounds using a Agilent J&W capillary column . Separated DMS was then transferred via a heated (200 °C) transfer line to a multi-collector inductively coupled plasma mass spectrometer  to determine its sulfur isotopic composition. Standard DMS and DMSP solutions with known δ34S values  were injected for calibration every four samples, and a bracketing technique was applied to correct for instrumental mass bias49. Analytical precision and accuracy of DMS and DMSP analysis of standards were usually better than 0.2‰ (1σ standard deviation). The precision of sulfur isotope analysis for duplicate or triplicate samples of seawater or ice averaged 0.3‰ but in few extreme cases reached up to 1‰.Sulfur isotope measurements are presented in this study using the standard delta (δ) notation (δ42−]) precision of these analyses were around 20 nM. Split of this solution was treated with 10% BaCl2 solution and the BaSO4 analysed for its sulfur isotope composition by a conventional elemental analyser (EA) coupled to isotope ratio mass spectrometer (IRMS) method50 using Delta Plus, Thermo. The sulfur isotope reference materials NBS-127 , IAEA-S-1 , and IAEA-SO-6  were purchased from the National Institute of Standards and Technology (NIST) and used for calibration. Precision of this method for duplicates/triplicates was usually better than 0.3‰.Quantification of sulfate was determined from a melted ice cuboid. The melt aliquot was filtered with polycarbonate filters (0.45 μm) to remove particulate organic matter. Aliquot (50 μL) of the filtered solution was diluted 400× and introduced in a Dionex-ICS5000 liquid chromatograph for ion analysis  was always measured in situ with a fast-response handheld portable digital thermometer equipped with a calibrated probe (TESTO®720)51. The probe was inserted in 4 mm diameter holes drilled to the centre of the physical core at 5 cm intervals. The precision of the probe was ± 0.1 °C with an accuracy of ± 0.2 °C. Brine salinity (Sb) was directly computed from sea ice temperature (T) assuming thermodynamic equilibrium of the brine with surrounding ice52:Vb) (brine volume/bulk ice volume) was computed from sea ice temperature (T) and bulk ice salinity (S) using the equations of Cox and Weeks52 for ice temperature <−2 °C and of Lepparänta and Manninen for ice temperature ≥−2 °C53.Sea ice temperature 54. Then, the settled cells were visualized (measured and enumerated) using a Leica Leitz DM IL inverted light microscope equipped with 10× and 40× objectives and 10× and 12.5× oculars (magnification of 500×) with an attached digital camera (LeicaDC300F) for documentation. Species identification was based on Medlin and Priddle55, Thomas56, and Scott and Marchant57.Microalgal taxonomy was determined on the biology core through light microscopic cell enumeration in 200 mL aliquots of melted sea ice stored in brown glass bottles and preserved with acid Lugol’s solution. The bottles were stored in the dark until the cells were settled from a 50, 10, 2, or 1 mL volume for up to 24 hF. cylindrus were maintained in exponential growth at 4 °C and a salinity of 34 g kg−1 under a 16:8 light:dark cycle (75 μE m−2 s−1) in a refrigerated incubator (RUMED® Rubarth Apparate GmbH). F. cylindrus was grown in artificial seawater, created by mixing filtered (0.2 μm) Antarctic seawater from the McMurdo Sound area with artificial sea salts (Instant Ocean®) to a salinity of 100 g kg−1 , and diluting it with mQ water to a salinity of 34 g kg−1. This mixing was done because the volume of Antarctic seawater available was relatively limited. A standard f/2 medium was also added to the water58. These culture conditions are referred in the study as cold oceanic conditions.Cultures of F. cylindrus was initially grown under cold oceanic conditions  in 1 L Nalgene® bottles (inoculation: 5·106 cells mL−1). After 21 days, this control culture was sampled to determine the cell density, the carbon biomass, and the concentration in chlorophyll a, and DMSP (following the same purge and trap-GC procedure detailed above). The remaining volume of the 1 L culture was divided into sub-cultures (cultures in brine conditions). The salinity of both sub-cultures was modified by three additions  of the initial salt mixture  to reach a salinity of 75 g kg−1 . The temperature of the second sub-culture was simultaneously decreased to −4.4 °C by inserting the culture bottles in a cooling alcohol bath (PolyScience®). The cultures were then sampled after 24 h, 48 h, 72 h, and 1 week following the final salt addition and analysed for the same parameters as the control culture. Each culture (control and brine conditions) was treated with a set of antibiotics (penicillin-G and streptomycin)59 to limit bacterial contamination.In the experiment, 34S value in all the culture samples (control and brine conditions) as verified by EA-IRMS analysis of each solution (+6.5‰ ± 0.1‰). This allowed the determination of difference fractionation factors between sulfate and DMSP.The sulfur isotopic composition of DMSP in each culture (control and brine conditions) was determined by GC-MC-ICPMS as described above. Artificial sea salts additions to the cultures logically modified the isotopic signature of the source sulfate for DMSP synthesis. Since all culture waters  were prepared from the same initial salt mixture , this source sulfate had the same δSupplementary Information


Ecklonia species, which are marine brown algae having a ubiquitous distribution. In search of compounds having biological activity from macro algae during the past three decades, this particular compound has attracted massive attention for its multiple therapeutic properties and health benefits. Although several varieties of marine algae, seaweed, and phlorotannins have already been well scrutinized, eckol deserves a place of its own because of the therapeutic properties it possesses. The relevant information about this particular compound has not yet been collected in one place; therefore, this review focuses on its biological applications, including its potential health benefits and possible applications to restrain diseases leading to good health. The facts compiled in this review could contribute to novel insights into the functions of eckol and potentially enable its use in different uninvestigated fields.The marine biosphere is a treasure trove of natural bioactive secondary metabolites and the richest source of structurally diverse and unique compounds, such as phlorotannins and halo-compounds, with high therapeutic potential. Eckol is a precursor compound representing the dibenzo-1,4-dioxin class of phlorotannins abundant in the  Marine algae have been consumed as sea vegetables for the diet and ingredients in medicine since ancient times in countries including Korea, China, and Japan . One of d iodine . Polysacd iodine , carotend iodine  and astaEcklonia species and Ishige okamurae, have been considerably evaluated as these species contains phlorotannins [Ecklonia is the most abundant genus of kelp  associated with the Lessoniaceae family having an affluence of eckol-type phlorotannins.Among the marine seaweeds, brown algae, including otannins . Phlorototannins . AccordiEckol, a precursor compound illustrating the dibenzo-1,4-dioxin class of phlorotannins, contains phloroglucinol components linked to each other in multiple fashions . SeveralTherefore, understanding the biological activities of eckol to expand effective therapeutic approaches is very important. Although abundant information related to compounds from marine algae ,30,31,32The lack of balance between antioxidants and free-radicals in the body leads to oxidative stress. As free radicals react easily with other molecules in the human body, they can lead to large-chain chemical reactions called oxidation which can be useful or harmful.Human cells remove the ROS through their defense system by the mode of enzymatic and non-enzymatic pathways. When a body contains free reactive oxygen species (ROS) beyond its defensive capacity, the ROS can start damaging fatty tissue, nucleic acids, and proteins, which can give rise to a vast sum of diseases over time, including neurological disorders ,84, diab2O2). Through the pathway of phosphorylated AMP-activated protein kinase/forkhead box O3a (AMPK/FoxO3a), the MnSOD expression was induced by eckol. Eckol-stimulated MnSOD expression was reduced by 10–50 nM of specific silencing RNAs (siRNAs) against FoxO3a and AMPK. Additionally, the cytoprotective activity of eckol against H2O2-provoked cell death was reduced by diethyldithiocarbamate (a MnSOD inhibitor). Thus, by activating the AMPK/FoxO3a-mediated induction of MnSOD, eckol protected the cells against the oxidative stress in mitochondria [Manganese superoxide dismutase (MnSOD) is an antioxidant mitochondrial enzyme in exhibiting cytoprotective effects against oxidative stress. This enzyme is used as a marker to evaluate the antioxidant properties of phytochemicals. As an antioxidant, eckol at 10 µg/mL recovered MnSOD expression and activity that had been decreased by 600 µM hydrogen peroxide  (10 nM) and LY294002 (an inhibitor of PI3K) (5 μM). Therefore, eckol has the ability to attenuate oxidative stress-induced cell death through Nrf2-mediated HO-1 activation via Erk and PI3K/Akt signaling [Similarly, there was an induction of heme oxygenase (HO)-1 mRNA and protein expression in the Chinese hamster lung fibroblast (V79-4) cells in a concentration- and time-dependent manner, due to eckol, which resulted in high HO-1 activity. Enhancement of the phosphorylated form, nuclear translocation, antioxidant response element (ARE)-binding, and transcriptional activity of Nrf2 was observed in V79-4 cells upon exposure to 10 µg/mL of eckol. Furthermore, Nrf2 mediated the eckol-induced activation of the HO-1 promoter. The Nrf2 activation and induction of HO-1 expression were due to the contribution of the extracellular related kinase (Erk) and phosphoinositide 3-kinase/protein kinase B (PI3K/PKB). To further assess the likeliness of the cytoprotective activity of eckol due to HO-1 induction, the V79-4 cells were pretreated with HO-1 inhibitor zinc protoporphyrin (10 µM) and transfected with HO-1 siRNA (10–50 nM) and Nrf2 siRNA (10–50 nM). All of them markedly reduced the cytoprotective effect of eckol against Hignaling .Ecklonia cava had a cytoprotective effect against oxidative stress-induced cell damage in V79-4 cells. Eckol scavenged 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals, hydrogen peroxide (H2O2), hydroxy radicals, and intracellular ROS, with dose-dependent quenching effects. At 30 μM, eckol demonstrated a 79% radical scavenging effect on intracellular ROS. Eckol also prevented lipid peroxidation (31% at 30 μM) in a thiobarbituric acid reactive substances (TBARS) assay, reducing cell death in V79-4 cells which was induced by H2O2. After eckol treatment, there was a decrease in nuclear fragmentation and the apoptotic sub-G1 DNA content in V79-4 cells induced by H2O2. In addition, 30 μM eckol exhibited 47% and 43% ROS scavenging activity in cells damaged via serum starvation and γ-radiation, respectively. Eckol also influenced the activity of catalase by increasing it in a dose-dependent manner through the activation of phosphorylated ERK and NF-κB. Furthermore, eckol also increased the transcriptional activity of NF-κB. Hence, eckol is a capable of exhibiting cellular anti-oxidant activity and cytoprotection [Eckol isolated from Eisenia bicyclis was examined by the weight gain test [The antioxidant activity of five compounds, phloroglucinol, eckol, phlorofucofuroeckol A, dieckol, and 8,8´-bieckol from ain test . At a coE. cava extract on its antioxidant potential in airborne particulate matter (PM) (diameter < 10 μm (PM10)) exposed cultured keratinocytes. The cultured HaCaT keratinocytes exposed to PM10 in the presence and absence of E. cava extract were evaluated for their cell viability and cellular lipid peroxidation. Human epidermal keratinocytes exposed to PM10 (100 µg/mL) were used to examine the action of eckol and dieckol on cellular lipid peroxidation and cytokine expression.. There was a decrease in cell viability and an increase in lipid peroxidation when HaCaT cells were exposed to PM10, which was attenuated by E. cava extract  and its ethyl acetate (EtOAc) fraction (100 µg/mL). As compared to eckol (3 µg/mL), dieckol (10 µg/mL) attenuated cellular lipid peroxidation more effectively in both HaCaT cells and human epidermal keratinocytes. The inflammatory cytokines  expression was also attenuated by dieckol and eckol in human epidermal keratinocytes stimulated with PM10 [A recent study evaluated ith PM10 .Ecklonia maxima, four solvent-soluble fractions and three phlorotannins, phloroglucinol, dibenzo-1,4-dioxine-2,4,7,9-tetraol, and eckol were checked for their alpha-glucosidase inhibitory activity. The phloroglucinol derivative dibenzo-1,4-dioxine-2,4,7,9-tetraol (IC50 33.693 ± 0.61 µM) and eckol (IC50 11.163 ± 0.29 µM) displayed better inhibition than the positive control, acarbose (IC50 1013.35 ± 89.01 µM), showing eckol to be a potential compound for the treatment of hyperglycemia [Diabetes mellitus describes a group of diseases that affect how bodies use blood sugar (glucose). Chronic diabetic conditions include type 1 diabetes (T1DM) and type 2 diabetes (T2DM). With T1DM, the body does not make insulin, and in the more common T2DM (insulin-resistant state), the body fails to produce enough insulin or fails to respond adequately to insulin, leading to high glucose concentrations in the blood. The occurrence of severe hypoglycemia is related to intensive insulin therapy leading to research into antihyperglycemic agents focusing on traditional medicinal plants, as they could provide superior treatment as compared to synthetic drugs . The metglycemia . Ecklonia stolonifera-derived EtOAc fraction exhibited inhibitory effects against advanced glycation end-products (AGEs) formation and rat lens aldose reductase (RLAR) and yielded phloroglucinol, dioxinodehydroeckol, eckol, phlorofucofuroeckol-A, dieckol, triphlorethol-B, 2-phloroeckol, and 7-phloroeckol [E. stolonifera-derived phlorotannins exhibited RLAR inhibitory activity, with eckol showing an IC50 of 54.68 µM, although most of the isolated phlorotannins showed no activity in the AGEs inhibition assay. These results were in contrast to another study [Similarly, the oroeckol . The E. er study  in whicher study , the reaer study .E. stolonifera and E. bicyclis, fractions, and six isolated phlorotannins were tested against α-glucosidase and protein tyrosine phosphatase (PTP1B) enzymes. Eckol was characterized as a potent PTP1B inhibitor (IC50 2.64 µM) and a moderately potent α-glucosidase inhibitor (IC50 22.78 µM) [Further insight into the anti-diabetic potential of eckol was provided by another study in which the methanolic extracts of 2.78 µM) . Hence, As the liver operates by making proteins and blood clotting factors, producing triglycerides, cholesterol, bile, and synthesizing glycogen, it is one of the most important organs. The ability to prevent hepatic damage is vitally important as it is involved in the detoxification of xenobiotics and drugs .4) was used to investigate the protective effects of eckol in addition to the possible mechanisms. The CCl4-induced rise in the serum levels of alanine transaminase (ALT) and (49.43 ± 16.03 U/L) and aspartate aminotransferase (AST) (63.21 ± 18.89 U/L) were suppressed by the pretreatment of eckol at doses of 0.5 and 1.0 mg/kg/day for 7 days with the amelioration of morphological liver injury. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) analysis revealed the decrease in the number of apoptotic hepatocytes in the eckol-treated group as compared to the CCl4 model group. Eckol enhanced the expression of Bcl-2 and suppressed the expression of cleaved caspase-3, which reduced malondialdehyde formation, enhanced superoxide dismutase, glutathione peroxidase activity, and glutathione content, elevated TNF-α, and suppressed IL-1β and IL-6. Eckol also increased the level of IL-10, an anti-inflammatory cytokine with the recruitment of CD11c+ dendritic cells into the liver tissue of CCl4-treated mice. Thus, inhibiton of apoptosis, oxidation, and inflammation including immune regulation are the multiple mechanisms related to protective effects of eckol [An acute liver injury model in mice induced by carbon tetrachloride  having a low molecular weight exhibited no effect, unlike the high molecular weight phlorotannins eckol and dieckol. In conclusion, eckol is suitable as potential therapeutics for the treatment of hepatotoxicity as compared to other evalauted phlorotannins [In another study, hepatotoxicity in primary rat hepatocytes induced by doxorubicin was used to evaluate the hepatoprotective effects of 14 edible varieties of Korean seaweed. The otannins .E. stolonifera presented phlorotannins  through bioassay-guided fractionation that was determined to protect against cytotoxicity in the human liver-derived HepG2 cells induced by tacrine [50 values of 62.0 and 79.2 µg/mL, respectively, other compounds, including eckol (EC50 > 100), exhibited no activity in HepG2 cells against the cytotoxic effects of tacrine [Furthermore, the active EtOAc-soluble fraction of  tacrine . Except  tacrine .The age-dependent disorders which include neurodegenerative diseases are prevailing, as people are living longer than they did in the past . AlzheimE. bicyclis and its phlorotannins against β-secretase 1 (BACE1) was carried out. Eckol (IC50 12.20 µM) isolated from EtOAc soluble fraction showed significant activity against BACE1 [E. stolonifera yielded n-hexane fraction containing sterols, fucosterol, and 24-hydroperoxy 24-vinylcholesterol, and the EtOAc fraction containing phlorotannins, phloroglucinol, dioxinodehydroeckol, eckol, phlorofucofuroeckol-A, dieckol, triphlorethol-A, 2-phloroeckol, and 7-phloroeckol, where eckol exhibited significant AChE inhibition with an IC50 value of 20.56 ± 5.61 µM. Conversely, eckol exhibited no inhibitory activity against BChE, with IC50 values > 500 µM. This difference in activity can be explained by the fact that AChE is a substrate-specific enzyme in nerve synapse, whereas BChE is a non-specific enzyme in plasma and tissue showing involvement of specific binding properties of enzyme and substrate [In search of an anti-AD treatment derived from marine plants, the evaluation of the st BACE1 . Taking ubstrate .E. maxima and its crude extract, solvent-soluble fractions, and isolated phlorotannins, the IC50 values of the solvent soluble fractions ranged from 62.61 to 150.8 μg/mL, with the EtOAc fraction having an excellent inhibitory activity against AChE. Compounds isolated from the EtOAc fraction were identified as phloroglucinol and two of its derivatives, dibenzo-1,4-dioxine 2,4,7,9-tetraol and eckol. Dibenzo-1,4-dioxine-2,4,7,9-tetraol (IC50 84.48 ± 0.26 µM) and eckol (IC50 76.70 ± 0.35 µM) exhibited better inhibitory activity against AChE than phloroglucinol (IC50 579.32 ± 0.34 µM), suggesting that dibenzo-1,4-dioxine-2,4,7,9-tetraol and eckol could be effective as AChE inhibitors in treatment of AD [Similarly, in a study related to E. bicyclis were investigated for their effectiveness on their degree of human (h) MAO-A and hMAO-B inhibition. Eckol exhibited IC50 values of 7.20 ± 0.71 µM and 83.44 ± 1.48 µM against hMAO-A and hMAO-B, respectively. Mixed and non-competitive inhibitory mechanisms were revealed by biochemical and molecular docking examinations. Hence, eckol can be useful to manage PD and other neurological disorders through the inhibition of MAO [Since the inhibition of monoamine oxidase (MAO) is important in the management of PD, eckol and dieckol isolated from methanolic extract of n of MAO .A–benzodiazepine (BZD) receptor, a well-recognized target for sedative-hypnotics was used to test the binding activity of methanol extracts of 30 seaweeds. Among the seaweeds, the most active ethanol extract of E. cava significantly increased sleep in mice when induced by pentobarbital. Among the four separated solvent fractions, hypnotic activity was related to the content of total phenols and total phlorotannins in the seaweed. The highest activity was exhibited by the EtOAc fraction which constituted of phlorotannins eckol, dioxinodehydroeckol, dieckol, and triphlorethol-A. Eckol (iK 1.070 µM) and dioxinodehydroeckol (iK 1.491 µM) showed better binding at the receptor than triphlorethol-A (iK 4.419 µM) and dieckol (iK 3.072 µM). The hypnotic effects of the ethanol extract and its EtOAc fraction were inhibited by flumazenil which is a specific GABAA–BZD receptor antagonist. Hence, through the positive allosteric modulation of the GABAA–BZD receptor, the phlorotannins from EC, including eckol, induces sleep [Insomnia is currently a widespread sleep disorder worldwide leading to an increase in the use of natural sleep aids containing specific components of foods and herbal plants. Thus, these are becoming popular to enhance sleep quality and refrain side effects as compared to prescription sedative-hypnotics . Gamma-aes sleep .s/olf-coupled D1-like (D1 and D5) and Gαi/o-coupled D2-like  receptors [3 receptor (hD3R) and human D4 receptor (hD4R), respectively. At 50 μM eckol, the agonist response increased to above 50%, giving EC50 values of 48.62 ± 3.21 and 42.55 ± 2.54 μM for hD3R and hD4R, respectively. However, eckol did not show any modulating effect on dopamine D1, serotonin 1A (5-HT1A), vasopressin (V1A), tachykinin (NK1) or muscarinic (M5) receptors [hD3R receptor, forming five H–bond interactions. Similarly, eckol bound to the active site cavity of hD4R with a negative binding energy  that was lower than dopamine , possibly as a result of four H–bond interactions. Even though eckol did not form a salt bridge to the carboxylate group of Asp110 of hD3R and Asp115 of hD4R important for high-affinity ligand binding to dopaminergic receptors [3R. On the other hand, Phe346 displayed a hydrophobic interaction with eckol initiating a conformational change in the protein and ligand inside the binding pocket. Through π–π interactions, Phe346 also bound to eticlopride and dopamine contributing to the stabilization of ligand inside the binding pocket. The conserved serine residues in helix V also plays an important role as a molecular determinant for agonist-induced signaling from dopamine receptors. The Ser192 of hD3R (Ser197 of hD4R) and a hydroxyl moiety of eckol presented an H–bond interaction, implying eckol as a dual hD3/D4R agonist. A logPo/w value of 2.99, an excellent binding to plasma protein (100%) and a moderate human intestinal absorption of 55.60%, was predicted through in silico pharmacokinetic parameter PreADMET. Also, the in vivo blood–brain barrier penetration calculations showed a moderate absorption (25%) by the central nervous system. [The involvement of G-protein coupled receptors in human pathophysiology and their pharmacological traceability has emphasized on design and implementation of high-throughput G protein coupled receptor functional assays to identify novel drug candidates . Dopamineceptors . At a coeceptors . In the eceptors , it form system. . Although ionizing radiation can have health benefits as radiation therapy in the treatment of cancer or thyrotoxicosis, it is often narrowed down by the toxicity to the neighboring normal tissues and organs ,102. Nat60Co gamma-ray)-induced damage. Representing a significantly diminished death rate, 28.6% (4/14) of the irradiated, untreated group survived for 30 days after exposure to 9 Gy of WBI while 86.6% (13/15) of the mice survived for 30 days that received eckol plus irradiation. An endogenous colony-forming unit (CFU) assay revealed 2.3 ± 0.5 and 3.5 ± 0.5 endogenous CFUs from the eckol plus irradiation group and irradiation control group, respectively. The results did not alter for the non-irradiated group when treated with eckol alone. The revival of hematopoietic ability by the splenic progenitor cells due to the eckol was indicated by the 50% increase in the number of CFUs. A decrease in the percentage of tail DNA (14.7 ± 5.6%) after eckol treatment in irradiation-damaged lymphocytes as compared to the content of tail DNA (42.5 ± 8.7%) when exposed only to 7 Gy of WBI was shown by alkaline comet assay. Thymidine incorporation of splenocytes increased by two fold in 9 days in eckol-treated irradiated mice as compared to the untreated one. Furthermore, the number of CD3+ pan T cells and CD45R/B220+ pan B elevated in the eckol-treated irradiated groups as compared with the irradiated, untreated control groups. The increase in the number of CD3+T by 44.3% and CD45R/B220+ pan B cell population by 27.6% as compared with the irradiated, untreated controls confirmed the role of eckol in immunoprotection by elevating the revival rates of specific immune cells [It was ascertained that eckol at doses of 10 mg/kg body weight given 2 h and 18 h before exposure to 8, 9 or 10 Gy of whole-body irradiation (WBI) could save mice from radiation (ne cells .n = 6 per group) compared with the irradiated controls (crypts per circumference 8.6 ± 1.7). The number of surviving crypts also increased in gamma-irradiated mice (3.5 days irradiation (8 Gy)) pretreated with phloroglucinol and eckol as compared to the irradiated control, suggesting an improvement in the survival of the jejunal crypt in irradiated mice when treated with these compounds. The expression of apoptotic nuclei (occurring mainly in the lower third of the crypt) was increased by irradiation as shown by both hematoxylin–eosin staining and the in situ DNA end- labeling (ISEL) method. A decline in the number of apoptotic nuclei was observed 12 h after irradiation when pretreated with phloroglucinol and eckol as compared with irradiated control groups. Thus, improvement in jejunal crypt survival and shielding against apoptosis induced by radiation in mouse jejunal crypts was observed when pretreated with phloroglucinol and eckol [Eckol and dieckol were also examined for their radioprotective activity in intestinal stem cells. Pretreating gamma-irradiated mice (3.5 days irradiation (8 Gy)), with phloroglucinol (crypts per circumference 43.73 ± 15.87) and eckol (crypts per circumference 32.08 ± 17.96) remarkably increased the jejunal villi height  in vivo. To assess whether the effectiveness of eckol in inhibiting DNA damage was accountable to apoptotic changes, the nuclear morphology of lymphocytes was assessed in irradiated mice as peripheral blood lymphocytes are easily harmed by ionizing radiation. The number of apoptotic nuclei was reduced dramatically in the eckol treated group in comparison with the irradiated control group (9.95 ± 0.50% versus 14.85 ± 0.39%). Hence, the viability of peripheral blood lymphocyte was protected by inhibiting apoptotic cell death induced by ionizing radiation in vivo. The frequency of apoptotic fragments in crypt cells was reduced in the eckol-treated group by 16.63% compared to the untreated group (4.51 ± 0.30%) after 24 h of WBI treatment revealing the ability of eckol to protect intestinal crypt cells from radiation-induced apoptosis. The increase in the expression level of p53 and Bax, commonly seen after WBI, was also reduced by eckol with the induction in the expression level of Bcl-2, which is involved in apoptosis and DNA repair. In those ways, eckol treatment modulated the immunohistochemical localization and magnitude of apoptosis-related proteins in jejunal crypt cells. Therefore, eckol administration could provide great benefits for cancer patients by effectively preventing the apoptosis of peripheral blood lymphocytes and intestinal crypt cells induced by radiation [To further support the radioprotective potential of eckol, adiation . Furtheradiation . In addition to the human process of aging, the areas of the face, neck, and dorsum of hands and forearm get affected by the harmful effects of UV light. Photo aging results due to the continued UV exposure and sun damage on human aging skin  leading E. stolonifera, E. bicyclis, and E. cava exhibiting more potent inhibition of NF-κB and AP-1 than seaweeds from other families. They also showed protection against collagen destruction through the TNFα-induced inhibition of MMP-1 expression. Eckol and dieckol isolated from E. stolonifera diminished the expression of MMP-1 induced by TNF-α and basal expression of MMP-1, and reduced both NF-κB and AP-1 reporter gene activity in human dermal fibroblasts. Hence, these results indicate that the reduction of MMP-1 expression is due to the compounds eckol and dieckol [In matrix metalloproteinase (MMP) family, the expression of certain members is induced by UV irradiation. Matrix metalloproteinases are zinc-containing proteinases that degrade collagen and the other extracellular matrix proteins comprising the dermal connective tissue ,108,109. dieckol .The excessive generation of ROS causing oxidative stress in the skin is due to the UVB radiation ultimately damaging DNA, leading to cancer ,117. AccO--6,6´-bieckol, 6,6´-bieckol, 8,8´-bieckol, 7-phloroeckol, 2-phloroeckol, eckol, dieckol, phlorofucofuroeckol, phlorotannin A, fucofuroeckol A, and various minor homologues) against photo carcinogenesis in the SKH-1 hairless mouse skin model. A decrease in tumor incidence was seen when brown algal polyphenols were administered through diet (79%) and skin (94%) with moderate protection against skin carcinogenesis induced by UV-B radiation in mice. The propagation of tumor decreased from 8.54 ± 0.75 to 4.73 ± 0.74 (p < 0.005) and 3.75 ± 0.54 (p < 0.001) when treated with 0.1% and 0.5% brown polyphenols through diet, in tumors/tumor-bearing mice, exhibiting a 45% and 56% inhibition. On the other hand, topical administration of 3 and 6 mg of these compounds reduced tumor multiplicity from 8.45 ± 1.23 to 3.42 ± 0.56 (p < 0.001) and 4.56 ± 0.56 (p < 0.005), respectively, in tumors/tumor-bearing mice. They also suppressed the gene expression of cyclooxygenase (COX)-2, decreased PGE2 levels in the skin, inhibited the amount of COX-2 protein, and reduced the rate of proliferating cells in the epidermis. In summary, eckol exerts protective effects against skin carcinogenesis induced by UVB radiation [E. cava-isolated phlorotannins  and polyphenol were examined for their protective effect against UVB-induced photo-oxidative stress in human fibroblast cells. Eckol exhibited slightly low activity against UVB radiation-mediated ROS (174.4% ROS at 250 µM) as compared to dieckol (100.7% ROS at 250 μM) when the level of ROS was recorded as 234.1% in UVB-irradiated cells (positive control). Eckol showed cell survival rates of 45%, 50%, and 56% at concentrations of 5, 50, and 100 µM, respectively. The comet assay was performed to evaluate whether phlorotannins protected against DNA damage and revealed that eckol had about 21%, 43%, and 53% inhibitory activity at concentrations of 0.5, 5, and 50 µM, respectively [The desirability of developing effective chemo-preventive agents against UVB-induced skin cancer in humans has led to an assessment of the chemo-preventive efficacy of brown algae polyphenols . The ethanol extract consisted of phlorotannins which exhibited potent ACE inhibition: phloroglucinol (IC50 2.57 ± 0.09 mM), triphlorethol-A (IC50 2.01 ± 0.36 mM), eckol (IC50 2.27 ± 0.08 mM), dieckol (IC50 1.47 ± 0.04 mM), and dioxinodehydroeckol (IC50 2.95 ± 0.28 mM). Eckol showed lower IC50 than that of the weakest dioxinodehydroeckol. The protein-binding abilities of the phlorotannins occurring reversibly by hydrogen bonding or irreversibly through covalent condensations could be associated with the ACE inhibition [The regulation of blood pressure involves angiotensin-converting enzyme (ACE), a potent vasoconstrictor, whose role is to convert angiotensin I to angiotensin II. Hence, ACE inhibition plays a physiological role in the treatment of hypertension. Natural ACE inhibitors as alternatives with fewer side effects as compared to synthetic drugs have been a major interest for research in preventing hypertension . Among thibition . E. stolonifera, E. cava, Pelvetia siliquosa, Undaria pinnatifida, and Grindelia tenella. Since the marked ACE inhibitory activity was exhibited by crude extract of E. stolonifera, it was fractionated with several solvents in order to determine the ACE inhibitory properties between the concentrations of 32.69 and 169.72 μg/mL. Fucosterol and six phlorotannins  were successively isolated from the EtOAc fraction. Eckol, phlorofucofuroeckol-A, and dieckol displayed IC50 values of 70.82 ± 0.25, 12.74 ± 0.15, and 34.25 ± 3.56 µM, respectively, showing the importance of a closed-ring dibenzo-1,4-dioxin moiety to the observed ACE-inhibition [Similarly, significant inhibition of more than 50% at a concentration of 163.93 μg/mL was exhibited by the ethanol extracts of seaweeds which included hibition . Anticoagulants, commonly described as blood thinners, inhibit thrombin and factor Xa (serine proteases), which is promoted by stimulating the activity of serine protease inhibitor, SERPIN-antithrombin III. Difficulty in isolating heparin (primary anticoagulant) and its hemorrhagic side effects have driven researchers to isolate novel anticoagulants from natural sources without side effects .Ecklonia kurome to evaluate the structural requirements necessary for inhibition of α2 macroglobulin (α2-M) and α2 plasmin (α2-P) inhibitors. The main plasmin inhibitors in plasma include the α2-M and α2-P inhibitors. Eckol exhibited potent and specific inhibitory activity on the actions of α2-M (IC50 2.5 µg/mL) and α2-P (IC50 1.6 µg/mL). The synthesis of various methylated derivatives of eckol in this study and their inhibitory activity on the anti-plasmins implied that a simple dibenzo-1,4-dioxin skeleton bearing some functional groups could become a lead compound in the development of a new class of thrombolytic agents [Eckol was isolated from c agents .2-P (IC50 1.6 µg/mL), an α2-M (IC50 1.8 µg/mL), an α1 anti-trypsin (IC50 0.8 µg/mL), and thrombin (IC50 13 µg/mL) inhibitor. However, eckol exhibited very weak inhibition on anti-thrombin III-heparin complex and exhibited no inhibition on plasmin. The inhibitory activity of eckol was reduced in whole human plasma, but at a concentration above 200 μg/mL, it enhanced urokinase-induced fibrinolysis. The importance of dibenzo-1,4 dioxane skeleton for inhibition of plasmin inhibitors was shown by several derivatives of eckol [p-dioxin-1,3,6,8-tetraol) is important for the potent anti-inhibitor activity as compared to the other hydroxyl groups present in eckol. Hence, the results suggest that a simple dibenzo-1,4-dioxane skeleton with other functional groups could be clinically useful in stimulating fibrinolysis [In a similar study, eckol acted as an αof eckol . As prevof eckol , only thinolysis .Staphylococcus aureus (MRSA) and Salmonella isolates revealed the antimicrobial activity of eckol towards all the tested strains. The minimum inhibitory concentrations (MICs) of eckol towards S. aureus and Salmonella showed inhibition in a concentration-dependent manner, but all concentrations caused a reduction in CFUs over time, showing at least a 4 log10 decrease in the bacterial count after 4 h. Concentrations between 125 and 500 µg/mL showed bacteriostatic activity while that between 250 and 500 µg/mL inhibited the expansion of Salmonella for a period of 24 h. The fraction inhibitory concentration index ranged from 0.31 to 0.5 for the combination of eckol and ampicillin, showing a high inhibition against S. aureus when ampicillin was used in combination with eckol as compared to when it was used alone [Despite the boost in the expansion of antibacterial agents, the development of multidrug-resistant bacteria has created a special need for research on new antibacterial agents . As the ed alone .E. bicyclis with Candida utilis YM-1, which included eckol, dieckol, dioxinodehydroeckol, and phlorofucofuroeckol-A exhibited a strong anti-MRSA activity, with MIC values in the range of 128 to 512 μg/mL indicating a potent antimicrobial inhibition of MRSA and foodborne pathogenic bacteria [The EtOAc-soluble extract of fermentation broth of bacteria . Propionibacterium acnes (KCTC 3314), P. acnes isolate 2875, P. acnes isolate 2876, and Staphylococcus aureus (KCTC 1927), and a MIC value of 128 μg/mL for Staphylococcus epidermidis (KCTC 1370) [Also, eckol exhibited MIC values of 256 μg/mL for TC 1370) .E. cava led to bioactivity-guided fractionation and isolation of five phlorotannins . The inhibitory activity and kinetic behavior of these phlorotannins were examined against NA using various strains of influenza virus which includes A/Bervig_Mission/1/18 (H1N1), A/PR/8/34 (H1N1), A/Hong Kong/8/68 (H3N2), and A/Chicken/Korea/MS96/96 (H9N2). Eckol demonstrated a moderate IC50 value of 89.5 µM against A/Bervig_Mission/1/18 (H1N1), but failed to show any significant inhibition on the other virus strains (IC50 > 200 µM) compared with the other tested compounds . The IC50 of the compounds increased with the increase in hydroxyl groups (eckol to dieckol), indicating the significant and definite NA inhibitory activity due to the number of hydroxyl groups on the structure of phlorotannins [In the viral lifecycle, neuraminidase (NA) plays a critical role as a target in the development of drugs against influenza. A high NA-inhibitory activity (72.1% inhibition at 30 μg/mL) of EtOAc layer of ethanol extract of otannins . E. cava extract and its compounds. At low concentrations of 10 μg/mL, the extract, eckol, and phlorofucofuroeckol-A exhibited potent virus inhibitory activity. When there was simultaneous co-exposure of VHSV to extract, eckol, and phlorofucofuroeckol-A in the FHM, the inhibition rates increased (46.4–96.4%) as compared to the pre- (16.5–48.4%) and post-exposure (39.5–56.5%) strategies with the EC50 values of 4.76, 1.97, and 0.99 μg/mL for the extract, eckol, and phlorofucofuroeckol-A, respectively. Also, an increase in the exposure time led to high activity against the virus in the FHM cell line. After the oral administration of the extract to the olive flounder challenged with VHSV, the efficacy against VHSV resulted according to the VHSV challenge concentration and the dose of extract. The increase in proinflammatory cytokines  expression and the activation of IFN-α/β, ISG15, and Mx indicated the immunomodulatory and immunostimulatory effect of the extract [Similarly, viral hemorrhagic septicemia virus (VHSV) in the fathead minnow (FHM) cell line was used to test the inhibition efficacy of  extract . E. cava led to the isolation of eckol, 8,8’-bieckol, 8,4’dieckol, and phlorofucofuroeckol-A. 8,8´-bieckol, 8,4´dieckol inhibited HIV-1 reverse transcriptase (RT), and protease, whereas eckol and phlorofucofuroeckol-A failed to show any activity, even if they were produced from RT inhibitor fractions having ≥80% inhibition (100 mg/mL) [Human immunodeficiency virus (HIV) is a retrovirus affecting the cells of the human immune system and infecting the vital organs, ultimately causing immune deficiency and leading to acquired immune deficiency syndrome (AIDS). As there is an increase in failure in anti-AIDS treatment due to the strains of the virus becoming drug-resistant, the research for drug candidates with higher rates of inhibition against various strains of HIV is increasing with the major focus on naturally derived compounds and their derivatives. The bioassay-directed isolation of 0 mg/mL) .pro) in viral replication, a biological assessment was completed on the phlorotannins isolated from E. cava. In this study, the E. cava phlorotannins were shown to inhibit SARS-CoV3CLpro competitively in cell-free systems. Phloroglucinol, triphlorethol A, eckol, dioxinodehydroeckol, 2-phloroeckol, 7-phloroeckol, fucodiphloroethol G, dieckol, and phlorofucofuroeckol-A were isolated from the ethanol extract of E. cava. Except for phloroglucinol, all the other phlorotannins displayed inhibition on 3CLpro hydrolysis in a dose-dependent manner. The IC50 values ranged from 2.7 to 164.7 µM where eckol (IC50 8.8 µM) and dieckol (IC50 2.7 µM) exhibited potent inhibitory effect on SARS-CoV 3CLpro cell-free cleavage with eckol structure being essential and crucial for good inhibition of SARS-CoV 3CLpro [Given the importance of severe acute respiratory syndrome coronavirus 3C-like proteinase  of E. cava collected from Jeju (J-CA) or Gijang (G-CA) after 3 weeks of high-fat diet (HFD) induction. High- performance liquid chromatography revealed both G-CA (4.72 mg/g) and J-CA (12.98 mg/g) to be rich in eckol. The G-CA-HFD mice showed lower body weight and little weight gain (40% decrease), reduced ALT and cholesterol levels, significantly increased mRNA levels of peroxisome proliferator-activated receptor (PPAR)γ2, C/EBPα and sterol regulatory element-binding proteins (SREBP)-1C (adipogenic-related transcription factors), higher fatty acid synthase (FAS) as compared to PBS-HFD mice and J-CA-HFD mice, whereas the plasma glucose level showed a decrease in J-CA-HFD and G-CA-HFD as compared to PBS-HFD. Due to the relationship between obesity and T2DM with chronic inflammation, the expression of inflammatory cytokines, TNF-α, interleukin (IL)-1β, and the macrophage marker F4/80 was elevated in PBS-HFD mice as compared with the normal chow mice. The G-CA-HFD mice significantly decreased all the above inflammatory factors as compared to PBS-HFD mice. The increase in hepatic lipid while HFD feeding caused the development of non-alcoholic fatty liver conditions. Therefore, the lipid content in frozen liver sections was assessed with an obvious increase in lipid droplet accumulation in the PBS-HFD mice. In comparison to PBS-HFD mice, there was a decrease in lipid droplet and triglyceride content in G-CA-HFD and J-CA-FD mice. Also, the mRNA expression of acetyl-CoA carboxylase 1 (ACC1), FAS, and SREBP-1c (genes related to lipid metabolism) significantly decreased in the G-CA-HFD mice in comparison to the PBS-HFD mice [High food intake in the absence of exercise leads to obesity ,127 contHFD mice . E. cava extract containing three distinct phlorotannins , separated and purified by pectinase and cellulose, was examined on the adipogenesis of 3T3-L1 adipocytes. When 12.5, 50, and 200 µg/mL of extract was applied to the cells for 24 to 48 hours, the cell viability increased by 49.8%, 58.3%, and 65.5%, respectively; the glucose utilization decreased by 143.5 ± 14.6, 138.9 ± 7.3, and 96.7 ± 6.2 mg/dL, respectively; and triglyceride accumulation also decreased by 143.5 ± 8.7, 92.4 ± 1.3, and 77.1 ± 1.3 mg/dL, respectively. Treatment with 12.5, 50, and 200 µg/mL extract also decreased the lipid accumulation by 52.2%, 53.2%, and 62.6%, respectively in 3T3-L1 adipocytes, including a decrease in the expression of CCAAT-enhancer-binding proteins (C/EBP)β but not C/EBPδ or PPARγ. A decrease in the protein levels of SREBP-1c, adipocyte fatty acid binding protein, FAS, and adiponectin was also observed [Obesity is related to adipogenesis which is the process of pre-adipocyte differentiation into adipocytes due to the high energy input and lack of exercise. Adipogenesis is regulated by multiple processes, including pre-adipocyte proliferation, differentiation, and fatty acid oxidation and synthesis controlled by several factors. In one of the study, the inhibitory effects of enzyme-treated observed .E. bicyclis revealed significant inhibition on pancreatic lipase through porcine pancreatic lipase assay  leading to the isolation of eckol, fucofuroeckol A, 7-phloroeckol, dioxinodehydroeckol, phlorofucofuroeckol-A, and dieckol. Since eckol lacks ether linkage at the C-7 position of its phlorotannin skeleton, it exhibited much weaker activity against pancreatic lipase than fucofuroeckol A and 7-phloroeckol, having one phloroglucinol element in the same position. Also, the molecular weight difference between the compounds had no impact on their pancreatic lipase inhibitory activity. The existence of a phloroglucinol moiety in eckol structure at the C-7 position and the number of hydroxyl groups in eckol, fucofuroeckol A, and 7-phloroeckol might have positively influenced the inhibition of pancreatic lipase, probably through their unique receptor binding [Among the various potential targets for treating obesity in humans, pancreatic lipase holds great potential. Pancreatic lipase is involved in the absorption of triglycerides by the small intestine which eventually gets secreted by the pancreas. It is responsible for the hydrolysis of triglycerides into glycerol and fatty acids . An inve binding . The abnormal cell growth leading to invasion or spreading throughout the body can be defined as cancer. External factors  and internal factors  trigger the mutation in chromosomal DNA of normal cells, eventually resulting to cancer ,132. Alt+ cell population and concealed the expression of glioma stem-like cell markers and self-renewal-related proteins in the absence of cell death.The fusion of eckol with glioma stem-like cells diminished tumor formation and the anchorage-independent growth of cells on soft agar in xenograft mice. Eckol decreased the resistance of glioma stem-like cells to ionizing radiation and temozolomide. In addition, both the PI3K-Akt and Ras-Raf-1-Erk signaling pathways were blocked due to the eckol treatment in the glioma stem-like cell. Hence, eckol suppresses stemness and malignancies, and sensitizes glioma-stem-like cells to anticancer treatments, providing a novel therapeutic strategy specifically targeting these cells [As eckol exhibited a wide range of therapeutic activities, it was also tested against cancer. When treated with eckol, the glioma stem-like cell markers and self-renewal-related proteins changed their expressions, their ability to form spheres and anticancer treatment sensitivity. Eckol treatment effectively reduced the sphere formation, CD133se cells .E. maxima. The compounds were phloroglucinol, eckol, 7-phloroeckol, 2-phloroeckol, and fucosterol. The cytotoxic effects of the compounds were tested on a few cancer cell lines using the 3--2,5-diphenyl tetrazolium bromide (MTT) reduction assay. The results indicate that eckol had the highest activity against the selected cancer cell lines: HeLa cells, H157, and MCF7, making it a good candidate with prominent inhibitory activity against metastasis that could effectively reduce cell damage [In another study related to anti-cancer effects, four phlorotannins and fucosterol were isolated and characterized from l damage .The chemical or immunological stimulation of mast cells leads to the discharge of internal mediators, such as histamine, which is an indicator of cell degranulation, and diversity of several mediators of inflammation  including pro-inflammatory and chemotactic cytokines (TNF-α and ILs) leading to allergic diseases ,134.E. bicyclis and E. kurome phlorotannins exhibited potent inhibition in comparison to the popular inhibitors catechins and sodium cromoglycate. Phloroglucinol, eckol (trimer), phlorofucofuroeckol-A (pentamer), dieckol, 8,8’-bieckol (hexamers), and an unknown tetramer showed IC50 values of 280, >800, 140, 120, 40, and 650 µM, respectively, whereas catechin, epigallocatechin gallate, and sodium cromoglycate had an IC50 value of 620, 190, and 270 µM, respectively. According to the results, eckol (IC50 > 800 µM) showed no inhibitory effect on hyaluronidase activity [In one study, an in vitro assay related to hyaluronidase inhibition by phlorotannins was evaluated. The activity . E. cava. Their inhibitory potential on the release of histamine was evaluated by their ability to inhibit immunoglobulin E (IgE) and anti-IgE antibodies stimulated degranulation of KU812 cells. Fucodiphloroethol G, eckol, and phlorofucofuroeckol-A displayed 23.97%, 44.26%, and 34.54% of relative histamine release, respectively, at the highest concentration (100 µM). In both the KU812 and RBL2H3 cells, calcium ionophore A23187 mediated the inhibitory effect of the phlorotannins. The histamine release percentages in RBL-2H3 cells treated with fucodiphloroethol G, eckol, and phlorofucofuroeckol-A were 27.73%, 50.63%, and 34.18%, and the degranulation percentages of RBL-2H3 cells were 18.02%, 31.67%, and 20.80%, respectively. Eckol, having fewer hydroxyl functional groups than the other two compounds, showed less inhibition on the histamine release in both cell lines, particularly compared with fucodiphloroethol G comprising of 11 hydroxyl functional groups. The molecular structure and amount of phenol groups could be the important factors for fucodiphloroethol G and phlorofucofuroeckol-A for showing strong activity than eckol. Also there was a potent inhibition of the binding activity between IgE and its receptor (30.58% and 34.23%) when treated with the highest concentration of fucodiphloroethol G and phlorofucofuroeckol-A, whereas eckol displayed less inhibiton (47.60%) in the flow cytometric analysis [E. cava showed moderate antiallergic activity as compared to other compounds due to the structural differences amid the compounds in terms of the number of hydroxyl groups and the linkages among the phenol units, leading to different inhibitory activity. Similarly, histamine release assay was performed on human basophilic leukemia (KU812) and RBL2H3 to assess the anti-allergic activities of phloroglucinol derivatives, fucodiphloroethol G, eckol, and phlorofucofuroeckol-A isolated from 50 22.0 µM), the other isolated phlorotannins 6,8´-bieckol, 6,6´-bieckol, phlorofucofuroeckol-B, and 8,8´-bieckol, phlorofucofuroeckol-A showed inhibitory activity similar to or greater than epigallocatechin gallate. In model rats fed with a diet including Eisenia arborea, the allergy symptoms improved possibly due to the suppressive effects of the isolated phlorotannins on enzyme and release of histamine. According to Sugiura et al. , the supThe occurrence of infection, endotoxin exposure, or cell injury in the body results in complex defensive feedback called inflammation that basically leads to the revival of normal cell structure and function . There iE. bicyclis showed inhibition of barrier disruption mediated by LPS and trans-endothelial migration of leukocytes to human endothelial cells at a concentration of 10 μM. In addition, eckol inhibited acetic acid-induced hyperpermeability and leukocyte migration induced by carboxymethylcellulose–sodium in vivo. Interestingly, according to the results obtained, the hydrogen donating hydroxyl groups present in dieckol regulated its protection ability which was better than eckol [Eckol and its derivatives were evaluated for their barrier protective effects against proinflammatory responses in human umbilical vein endothelial cells (HUVECs) and in mice. According to the results, the eckol and dieckol isolated from an eckol .Similarly, the signaling pathways involved in the protective actions of eckol and dieckol, including phloroglucinol, against pro-inflammatory responses in HUVECs and in high-mobility group box 1 (HMGB1) protein-treated mice were investigated. These phlorotannins inhibited LPS (100 ng/mL)-induced HMGB1 release and the expression of Toll-like receptor 4. In addition, they also inhibited barrier disruption medidated by HMGB1, the expression of cell adhesion molecules (CAMs)  and trans-endothelial migration of leukocytes to human endothelial cells. In addition, they suppressed hyperpermeability induced by acetic-acid and leukocyte migration induced by carboxymethylcellulose in vivo. To further explain the importance of hydroxyl group for the protective action, a change with the methyl group at the hydroxyl position of dieckol, diminished the vascular barrier protective effects . 2s (sPLA2s) are esterases cleaving glycerophospholipids at the sn-2 position, ultimately liberating a fatty acid and a lysophospholipid [E. bicyclis were evaluated for their potential inhibition on bee venom, porcine pancreas secretory phospholipase A2, soybean lipoxygenase, 5-LOX, COX-1, and COX-2. In the case of the bee venom sPLA2, the phlorotannins eckol, phlorofucofuroeckol-A, dieckol, 8,8´-bieckol, resveratrol, and epigallocatechin gallate demonstrated IC50 values of 120, 130, 160, 180, 170, and 110 μM, respectively. Eckol, phlorofucofuroeckol-A, dieckol and 8,8’-bieckol showed high activity in comparison to the positive controls resveratrol and epigallocatechin gallate. In porcine pancreas sPLA2, eckol, phlorofucofuroeckol-A, dieckol, and 8,8’-bieckol demostrated IC50 values of 100, 150, 90, and 180 μM, respectively. Eckol showed less inhibition against soybean lipoxygenase (LOX) and 5-LOX than 8,8´-bieckol, which was the potent inhibitor of soybean LOX, showing inhibition of more than 90% at 50 μM, and 5-LOX (IC50 24 µM). The phlorotannins had negligible inhibitory effects on COX-1 and COX-2, with eckol exhibiting 43.2% inhibition of COX-2 at 100 μM [The arachidonic acid (AA)-derived lipid-mediator secretory phospholipase Apholipid  that arepholipid . Anothert 100 μM .P. acnes bacteria [P. acnes-induced inflammatory response in HaCaT cells is due to MMP-2 and MMP-9 [P. acnes activated the NF-κB pathway, which is related to inflammatory mediators TNF-α, iNOS, and COX-2, and also the phosphorylation of p65 (an activated NF-κB subunit). Eckol gradually decreased all those activations in a concentration-dependent manner. Whereas treatment with P. acnes accelerated the phosphorylation of Akt which was inhibited by eckol in HaCaT cells [In acne vulgaris, bacteria  stimulatbacteria . With anbacteria . The P. nd MMP-9 . Eckol (aT cells .O-tetradecanoylphorbol-13-acetate (TPA), and oxazolone (OXA) were used as three sensitizers for inducing ear edema of Institute of Cancer Research (ICR) mice. Eckol, 8,8’-bieckol, phlorofucofuroeckol-A, and phlorofucofuroeckol-B suppressed ear edema at a dose of 0.01 or 0.1 mg. The phlorotannins behaved more strongly towards ear edema when treated with AA and OXA rather than TPA. All the sensitizers were inhibited by the phlorotannins in a similar manner to epigallocatechin gallate  [In another study, arachidonic acid (AA), 12-hibitor) . E. arborea purified six phlorotannins  were administered orally to mice initially, who were then evaluated for inhibitory effects of the compounds on swelling of the ears. To determine the suppressive ability of phlorotannins, a cultured mast cell model using RBL-2H3 cells was evaluated against the release of histamine, leukotriene B4, or prostaglandin E2 including their mRNA expression and the activity of COX-2. Eckol and 6,8′-bieckol suppressed degranulation at a concentration of 100 μM in RBL cells, compared with epigallocatechin gallate. As a result, all the phlorotannins showed potent inhibition with 6,8´-bieckol, 8,8´-bieckol, phlorofucofuroeckol-A having the highest activity [Following the above research, activity .E. stolonifera were investigated on lipid levels in the serum of hyperlipidemic rats. A high-cholesterol diet or poloxamer 407 was used to induce hyperlipidemia in rats. The rats fed with a high-cholesterol diet showed elevated levels of TC (255.6 ± 8.7 mg/dL), TG (240.2 ± 14.0 mg/dL), and LDL-C (145.1 ± 10.4 mg/dL) in the serum, as well as an increased atherogenic index (A.I.) (3.47 ± 0.4). Eckol at a dose of 20 mg/kg of body weight once a day for 3 days, reduced the serum TC (157.0 ± 9.7 mg/dL), TG (174.9 ± 14.6 mg/dL), LDL-C (63.1 ± 10.1 mg/dL), and A. I. (1.77 ± 0.3). In addition, the HDL-C level of hyperlipidemic control rats induced by poloxamer 407 was 59.9 ± 5.6 mg/dL, and that of the eckol-treated rats increased to 66.2 ± 5.2 mg/dL [Increase in the level of lipids  in the blood leads to several acquired or genetic disorders referred to as hyperlipidemia. Cardiovascular or heart diseases are the major complications of hyperlipidemia prevented through the appropriate use of medications and a healthy lifestyle. In search of anti-hyperlipidemic agents, the effects of eckol and dieckol isolated from ethanolic extract of .2 mg/dL .E. stolonifera, its fractions, the phlorotannins isolated from them, and the conjugated diene formation of the methanolic extract was investigated on in vitro Cu2+-induced human LDL oxidation. The thiobarbituric acid reactive substances (TBARS) assay revealed that the methanolic extract had concentration-dependent inhibitory activity against LDL oxidation induced by Cu2+, with an IC50 value of 5.66 ± 0.05 µg/mL, while the EtOAc fraction of E. stolonifera showed very high inhibition, with an IC50 value of 3.04 ± 0.13 µg/mL. Among the isolated phlorotannins , phlorofucofuroeckol-A and dieckol were found to be potent Cu2+-induced LDL oxidation inhibitors. Eckol showed moderate inhibition exhibiting an IC50 value of 7.47 µM. Because the production of conjugated dienes indicates the start of LDL oxidation, the lag time can be used as a measure of LDL oxidation resistance. Eckol extended the lag time to 54 min at 1 µM, 97 min at 5 µM, and 117 min at 10 µM. Probucol, the positive control, increased the lag time to 55 min at 1 µM, 74 min at 5 µM, and 91 min at 10 µM, thus, eckol was more effective than probucol at inhibiting conjugated diene formation [Because the oxidation of LDL is one of the causative agent of atherosclerosis, the inhibitory effects of ormation .l-tyrosine by oxidation, as in the blackening of a peeled or sliced potato exposed to air [E. stolonifera showed high tyrosinase inhibitory activity. The phlorotannins isolated from the active EtOAc-soluble fraction of E. stolonifera were phloroglucinol, dioxinodehydroeckol, eckol, phlorofucofuroeckol-A, and dieckol showing IC50 values of 92.8, 126, 33.2, 177, and 2.16 µg/mL, respectively, against mushroom tyrosinase. Phloroglucinol and eckol displayed higher inhibition than arbutin, and dieckol showed a three times higher inhibition than kojic acid. A non-competitive inhibition against mushroom tyrosinase was exhibited by eckol, phlorofucofuroeckol-A and dieckol with iK values of 1.9 × 10−5, 1.4 × 10−3 and 1.5 × 10−5 M, respectively [Tyrosinase is a copper-containing enzyme that catalyzes the production of melanin and other pigments from d to air . Improved to air . Out of ectively . E. cava was evaluated on melanogenesis and its binding capacity using a molecular docking simulation. The impact of eckol on melanin synthesis was evaluated in B16F10 melanoma cells induced by the α-melanocyte stimulating hormone. Eckol (25–100 μM) suppressed melanin synthesis and tyrosinase activity by inhibiting tyrosinase, both TRP1 and TRP2, expression in α-MSH-stimulated B16F10 cells. As compared to 50–100 μM eckol, 350 µM of arbutin (positive control) presented a weaker inhibition on tyrosinase activity [In a similar study of tyrosinase inhibition, eckol derived from activity .As in other fields, eckol has shown promising results in anti-hair loss, anti-hearing loss, and anti-osteoporosis treatments.E. cava on the promotion of hair growth. Treatment with E. cava enzymatic extract and compounds isolated from it resulted in the proliferation of immortalized vibrissa dermal papilla cells (DPCs). The DPCs were treated with compounds isolated from E. cava enzymatic extract including eckol, dieckol, phloroglucinol, or triphlorethol-A at a concentration of 0.005, 0.01, 0.05, 0.1, 0.5, 1, and 10 µg/mL for 4 days, which resulted in proliferation of DPCs by 100.8%, 106.1%, 120.3%, 108.5%, 107.8%, 105.4%, and 104.1%, respectively. Since the mitotic effect on NIH3T3 fibroblasts via the KATP channel opening leads to the promotion of hair growth, the E. cava enzymatic extract, eckol, dieckol, phloroglucinol, and triphlorethol-A were tested for their ability on hair growth. Eckol increased the proliferation of NIH3T3 fibroblasts to some extent as compared with the control group. Eckol and dieckol also inhibited 5α-reductase activity in a dose-dependent manner which is important for preventing hair loss [Hair loss, also known as alopecia or baldness, describes the loss of hair from the head or body, with severity varying from a small section to the whole body. One study evaluated the effect of air loss .E. cava (PPEE) was evaluated which resulted in decreased ROS levels. The notable compounds in PPEE were typical polyphenols found in E. cava which included dieckol (16.8%), phlorofucofuroeckol-A (3.5%), and eckol (1.9%), contributing to its anti-oxidant potential. The intraperitoneal administration of PPEE (100 mg/kg) and saline to the mice with exposure to noise significantly decreased the auditory brainstem response threshold shifts and provided a significant degree of protection in relation to the distortion product otoacoustic emission levels. Thus, eckol containing PPEE may have good potential to break the vicious cycle of TTS [In another study, the protective effect of eckol was linked to anti-hearing loss activity by preventing the temporary threshold shift (TTS). The implications of noise-induced hearing loss (NIHL) has received a lot of consideration among teenagers in recent years. Temporary threshold shift, which is a type of NIHL, accelerates the age-related hearing loss even if it is a transient one. As the primary cause of TTS is ROS, the protective activity of polyphenolic extract of e of TTS .E. cava and its bioactive constituents were tested for their effects on the adipogenic differentiation of 3T3-L1 fibroblasts and the osteoblast differentiation of MC3T3-E1 pre-osteoblasts. Triphlorethol-A, eckol, and dieckol at 20 µM exhibited anti-adipogenic activity by reducing lipid aggregation and by suppressing the expression of adipogenic differentiation markers. They also enhanced osteoblast differentiation which was shown by raised alkaline phosphatase action, increased levels of indicators related to osteoblastogenesis, and also affected intracellular calcification. Dieckol was the most active compound followed by triphlorethol-A and eckol against osteoporotic conditions [The bone-related disorder leading to an imbalance in bone mass is osteoporosis treated by the formation of bone tissue through osteoblast differentiation together with suppression of the possible causes of bone volume loss . But thenditions .4-induced toxicity in mice model. Hence, why eckol failed to protect the liver cell against tacrine-induced toxicity needs further detailed research to know the exact mechanism involved. In neuroprotection, the GABAA–BZD receptor and dopamine receptors hold a good future for eckol due to its potent activity against these receptors [hMAO-B inhibition [p-dioxin-I,3,6,8-tetraol) of eckol seems to be one of the major factors involved in the anticoagulative effect which requires further investigation. Although eckol showed potent anticoagulative effect via thrombin activity inhibition, the activity was reduced in whole plasma [As outlined in the above review, eckol has been evaluated copiously for a broad spectrum of activities to establish it as a potential therapeutic agent. According to various experimental results, eckol possesses a wide array of therapeutic properties. Through various studies ,43, eckoeceptors ,56. The eceptors  explainshibition . Althoughibition ,63,64, thibition ,60 by schibition  also suphibition ,120, thee plasma  most proe plasma  also supe plasma . Still ie plasma ,76, eckoe plasma ,73 or ine plasma  against e plasma ,67,124, e plasma  and the e plasma  could bee plasma  and antie plasma  activitiNumerous efforts to establish natural biomarkers for the treatment of various ailments have improved our understanding of their functions and activity. Considering the diversity of natural biomarkers such as eckol, a definite push is required to further decode these kinds of compounds for their proper use. Eckol exhibiting several biological activities is extraordinary, particularly the involvement of eckol as an anti-oxidant, anti-diabetic, radioprotective, hepatoprotective, and anti-inflammatory agent to name some. The use of eckol as anti-hair loss and anti-hearing loss is a refreshing new discovery. Increasing the scope of eckol as a neuroprotective agent by evaluating it against G protein coupled dopamine receptors is also a novel exploration for the treatment of major neurodegenerative disorders like Alzheimer’s and Parkinson’s disease. Thus, introducing eckol to various new receptors related to different diseases, other than the usual ones, could be of great interest. Since eckol exhibits activity against life-threatening disease like cancer, further research in this particular field also holds great potential for eckol to be established as an anti-cancer agent. The major reason for the broad spectrum of activity related to eckol is possibly due to its structure. Even the other potent phlorotannins of the same family have a basic backbone of eckol. So, developing eckol as a single pharmaceutical product could be beneficial in the field of medicine. Hence, natural product-derived compounds hold a multitude of opportunities for the discovery of novel therapeutic agents. The shift in focus from synthetically developed agents to natural agents could be a stepping stone for further advancements in the treatment of various infirmities. In conclusion, these kinds of naturally derived drugs have immense potential for advancement in the pharmaceutical and medical fields, leading to a definite change in views.


A large volcanic sulfate increase observed in ice core records around 1450 C.E. has been attributed in previous studies to a volcanic eruption from the submarine Kuwae caldera in Vanuatu. Both EPMA–WDS  and SEM–EDS  analyses of five microscopic volcanic ash (cryptotephra) particles extracted from the ice interval associated with a rise in sulfate ca. 1458 C.E. in the South Pole ice core (SPICEcore) indicate that the tephra deposits are chemically distinct from those erupted from the Kuwae caldera. Recognizing that the sulfate peak is not associated with the Kuwae volcano, and likely not a large stratospheric tropical eruption, requires revision of the stratospheric sulfate injection mass that is used for parameterization of paleoclimate models. Future work is needed to confirm that a volcanic eruption from Mt. Reclus is one of the possible sources of the 1458 C.E. sulfate anomaly in Antarctic ice cores. Tambora eruption4. Ice core studies first suggested the occurrence of a large volcanic event around 1450 C.E. based on glaciochemical evidence in a South Pole ice core5, a large electrical conductivity spike at 1460 C.E. in East Antarctica6, and a sulfate increase between 1380–1460 C.E. in a South Pole ice core7. The Greenland ice sheet acidity record also shows a modest increase at 1450 C.E.8, which was not thought to be a tropical volcanic event at the time. Later, Pang9 tied the southern hemisphere ice core anomaly to a large volcanic event from Kuwae volcano in Vanuatu primarily utilizing historical reports and tree ring data. The Kuwae caldera collapse was first suggested to have occurred in 1425 C.E., based on historical reconstructions and radiocarbon dating10. The timing was shortly revised by Robin et al.11 to 1452–1453 C.E. by combining 14C and ice core chronologies. Published tree ring frost damage12 and density data13 were interpreted as being the result of a strong cooling in the northern hemisphere in 1453 C.E., seemingly confirming 1452 C.E. as the start of the major volcanic eruption.The second largest sulfate loading event in the last 2500 years has long been thought to originate from the Kuwae caldera in Vanuatu. This event would be second only to the 1259 C.E. Samalas eruption in Indonesia16 accepted the 1452 C.E. age and Kuwae as the source caldera. At odds with this are proximal volcanological data collected at Tongoa and Tongariki islands17, reported as a sequence of subaqueous deposits with no evidence of widespread fall deposits that would be expected for a large caldera-forming eruption. The same report also disputed early historical evidences, and pointed to early radiocarbon dates18. This information did not influence the attribution of the largest sulfate signal observed in the developed 2000-yr Law Dome ice core record around 1458 C.E. to the large caldera forming event from Kuwae19.A number of Greenland and Antarctic ice core studieseVolv2k compilation of stratospheric volcanic injections listed the 1458 C.E. event as the third largest since 500 B.C.E., but Kuwae was not identified as a potential source20. Updated tree-ring based paleoclimate reconstructions strongly support a major cooling event in 1453 C.E. in the Northern Hemisphere21, implying that a large tropical volcanic event occurred in 1452 C.E. There are no similar reconstructions yet available for the Southern Hemisphere.Recently, the 22. The new methodology has made it possible to correlate tephra deposits located thousands of kilometers from source volcanoes24. Here we test the proposed source of this large 1450s enigmatic sulfate signal by investigating the geochemical composition of cryptotephra (micron sized volcanic glass particles) extracted from ice sampled between 72.53–72.63 meters depth of the South Pole Ice Core (SPICEcore) from Antarctica  in various depositional media2, ~3 wt.% Na2O and K2O, and ~2 wt.% FeO. Figure 26, a 2% uncertainty for SEM-EDS analyses was established and observed standard deviation of a secondary standard rhyolite glass fit within this parameterization .The particles found in the SPICEcore are rhyolitic with ~75 wt.% SiO2O and CaO, can be explained by the particles being unpolished. Rough surface geometry is known to cause some geochemical variations27. Iverson and others26 established that for some major element oxides, unpolished SEM-EDS measurements are robust enough to be useful for geochemical comparison despite a high standard deviation. In addition, the microprobe results show generally higher Na2O wt% compared to the SEM-EDS measurements. This is expected because microprobes are configured to measure Na2O in the first counting period during EPMA tephra analyses, whereas all elements are measured simultaneously during SEM-EDS analyses (longer counting time could result in Na loss on the SEM/EDS), and the SEM-EDS measurements are on unpolished particles, which increases variability of the results.We observed Fig.  slight vet al.11 define a basic to intermediate geochemical composition 29 around 0.5 . Therefore, the age alone makes Kaharoa tephra an unlikely candidate for the SPICEcore tephra deposits match. In a very comprehensive volcanism record from New Zealand there are no other identified eruptions from New Zealand around the 1450’s, which makes New Zealand volcanism an unlikely source for the tephra extracted from the SPICEcore, despite a very similar geochemical signature , and a volcanic eruption from these regions could be a source for SPICEcore tephra deposits. Antarctic volcanism during the last 1000 years typically has a basic composition38 can possibly be attributed to different volcanic eruptions occurring in the northern hemisphere. Several moderate eruptions occurring in both hemispheres over a short time frame could have complex global effects on atmospheric circulation patterns and temperatures39. Location sources and potentially different timing for signals attributed to a large volcanic eruption from the Kuwae caldera call for revision of parameterization values for ice core based volcanic forcing time series used in climate models since the pioneering work of40.The highly variable magnitude and duration of the sulfate peak observed in many Antarctic ice core records Figs , S1 favo21. Therefore, the proposed use of a 1458 C.E. event for bipolar synchronization1 should be reevaluated.In addition, the 1458 C.E. Antarctic sulfate signal timing should not be used to adjust the Greenland sulfate signal originally observed at 1452 C.E.This study presents the first quantitative EPMA-WDS and EDS-based geochemical data set on volcanic glass particles extracted from the 72.53–72.63 m depth of the SPICEcore. These new data challenge the majority of previous studies that have suggested that the large sulfate peak present during the ~1450’s C.E. time interval is associated with a large tropical eruption from the Kuwae volcano in Vanuatu, while providing further evidence toward the emerging volcanological and historical data that question such attribution. An accurate determination of the volcanic eruption source and magnitude is important and data presented here suggest that Kuwae has been incorrectly used in past climate model simulations as a source of the ca. 1450s C.E. large sulfate signal in polar ice cores. Although no volcanic source is unambiguously identified in this research, particle size and sulfate appearance in many Antarctic ice core records suggest the eruption is likely affiliated with a tropospherically transported aerosol cloud. A reasonably good geochemical match of SPICEcore tephra with the Reclus volcano and relatively recent, compositionally similar reworked tephra in Laguna Potrok Aike, provide a basis for a preliminary conclusion that possibly an unknown Reclus eruption is responsible for the volcanic signal in Antarctic ice cores. These data contribute to the Antarctic tephra framework needed for future tephrochronological studies, and suggest that paleoclimate models using Kuwae as a climate-forcing event for the ca. 1450 C.E. climate anomaly need to be revised.41. In the final version of the SP19 time scale, developed using ECM, visual layer counting, sodium and magnesium ions measurements, interpolation between 251 stratigraphic volcanic tie points to the WD2014 chronology, and previously published South Pole ice core records, the increase in electrical conductivity starts around 1459 (±2) C.E. and lasts for two years25. The remarkable manifestation of the sulfate-based volcanic record at the South Pole is attributable to low contributions of sulfate from dust, biogenic, and anthropogenic sources as well as stratospheric air masses5. Supplementary Figs The sampled interval targeted to locate and extract tephra associated with the 1450s sulfate anomaly was initially selected based on the preliminary version of the SP19 timescale. We sampled two depth intervals: 72.43–72.525 m (sample AntT-335) and 72.525–72.63 m (AntT-336). The sampling was guided by the age of an electrical conductivity (ECM) anomaly in the SPICEcoreμm in size) were captured and analyzed using a Tescan Vega-II XMU scanning electron microscope (SEM) equipped with an EDAX Apollo SSD40 energy dispersive spectrometer (EDS). The particles were analyzed on a single spot with a 140 pA beam for 100 seconds of live time at 15 kV of accelerating voltage. Major element oxides were calculated and adjusted using the semi-quantitative EDAX Genesis PhiRhoZ internal quantification procedure and the USNM 72854 VG-568 rhyolitic glass standard. The two largest particles were then polished and subsequently reanalyzed using a Cameca SX-100 electron microprobe equipped with five wavelength dispersive spectrometers (WDS). All measurements were made using instrumentation at the University of Maine. Analytical settings are discussed in Supplementary methods.Using improved ice core tephra mounting methodologies (see online Supplementary section for more details), five tephra particles (ca. 5–50 http://www.usap-dc.org.All analytical cryptotephra geochemical data shown in Figs Supplementary materialsTable S1Table S2Table S3Dataset Figure 1Dataset Figure 2 and S3