Two New Clerodane Diterpenes from Tinospora sagittata
Two new clerodane-type diterpenes, tinosporins C (1) and tinosporins D (2) were isolated from the stems of Tinospora sagittata (Oliv.), together with three known ones, columbin (3), tinophylloloside (4), and tinospinoside D (5). The structures of these compounds were determined on the basis of spectroscopic data interpretation, with that of the absolute configuration of compound 1 was assigned by experimental and calculated ECD spectra. The cytotoxicity and α-glucosidase inhibitory activities of isolated compounds were evaluated in vitro.
Two new rearranged clerodane diterpenes from Thai Tinospora baenzigeri
Abstract A new rearranged clerodane-type diterpene ( 1 ), tinobaenzigeride, and a new rearranged clerodane glucoside ( 2 ) were isolated from the stems of Tinospora baenzigeri , along with four known compounds ( 3 ‒ 6 ). Their structures were elucidated by spectroscopic data analysis. In addition, the structure and configuration of 1 was confirmed by single-crystal X-ray diffraction analysis. Compound 1 are a rare example of rearranged clerodanes, since it contains a fully oxygenated tetrahydrofuran moiety. The isolated compounds were evaluated for their cytotoxicity against Hep-G2 and MCF-7 cancer cells, none of them did show any significant activity at 25 μM. Graphic abstract
The peculiar thermo-structural behavior of the anionic lipid DMPG.
Aqueous dispersions of the anionic phospholipid dimyristoyl phosphatidylglycerol (DMPG), around 100 mM ionic strength, are known to exhibit a thermal behavior similar to that of the largely studied lipid dimyristoyl phosphatidylcholine (DMPC), which undergoes a gel to liquid crystalline phase transition at 23 degrees C, well characterized by differential scanning calorimetry (DSC), and other methods. However, at low ionic strength, DMPG has been shown to present a large gel-fluid transition region, ranging from 18 to 35 degrees C. This intermediate phase is optically transparent and characterized by a continuous change in membrane packing. Structural properties of the DMPG gel-fluid transition region will be discussed, based on results obtained by several techniques: electron spin resonance (ESR) of spin labels at the membrane surface and intercalated at different depths in the bilayer; light scattering; DSC; small angle X-ray scattering (SAXS); and fluorescence spectroscopy of probes in the bilayer.