γ-Pyrone derivatives fromHalenia corniculata
From 500 g of the epigeal part of Halenia corniculata (L.) Cornaz., collected in the Pribaikal region of the Buryat ASSR in July 1975, by extraction with 70% ethanol followed by treatment with chloroform we have isolated 32.7 g of extractive substances. Chromatography of the chloroform extract on silica gel with elution by chloroform yielded substances (i) and (2) of xanthone nature, and chloroform-ethanol (9:1) yielded luteolin, which was identified by its UV, mass, and PMR spectra and by comparison with an authentic sample [i].
Iridoids and Flavonoids of Four Siberian Gentians: Chemical Profile and Gastric Stimulatory Effect
Some Gentiana species have been used by the nomadic people of Siberia as bitter teas or appetizers to eliminate digestive disorders (dyspepsia, heartburn, nausea, etc.). We studied the most frequently used gentians: Gentiana algida, G. decumbens, G. macrophylla and G. triflora. The aim of the present study was to evaluate the phytochemical features and gastrostimulatnt activity of these four gentian herbs. Five iridoids, seven flavones and mangiferin were detected in gentian herbs after analysis by microcolumn-RP-HPLC-UV-ESI-MS. A componential phytochemical profile of the G. decumbens herb is presented for the first time, as well as information about distinct phytochemicals found in gentian herbs. HPLC quantification of the specific compounds of gentian herbs demonstrated the high content of iridoids (24.73–73.53 mg/g) and flavonoids (12.92–78.14 mg/g). The results of biological activity evaluation of four gentian decoctions demonstrated their good ability to stimulate acid-, enzyme- and mucin-forming functions of the stomach attributed to mostly by iridoids and flavonoids. In general, it can be claimed that the gentian decoctions can be used as effective and safe appetizers and are also a good source of biologically active agents.
Modelling of Mooney viscosity relaxation in natural rubber
Abstract Better assessment of natural rubber (NR) quality and processability, through the identification of new attributes, is still a major challenge. With this scope, 12 model samples of natural polyisoprene and two of synthetic polyisoprene were characterized in terms of Mooney torque relaxation, using the standardized ISO289 method (ML(1+4)100, explained later in the Section 1 ). The main purpose of this study was to identify a model that gave a better fit for the experimental decay of Mooney torque over time (ML(t)=f(t)) than the usual power law model used before (Y=at−b, [G.M. Bristow, A.G. Sears, The use of novel parameters in the assessment of natural rubber processability, NR Technol. 18 (1987); H.G. Burhin, W. Spreutels, J.M. Campbell, MV2000 Mooney viscometer: Mooney relaxation measurements on raw polymers and compounded rubber stocks, Kautsch. Gummi Kunstst. 43 (1990) 431]). The results showed that a generalized Maxwell model, and the Wu–Abbott empirical model ( Y = 1 − a Ln ( t ) − ( b t / ( c + t ) ) ) [T. Wu, J.A. Abbott, Firmness and force relaxation characteristics of tomatoes stored intact or as slices, Postharvest Biol. Technol. 24 (2002) 59–68], recently used for describing stress relaxation of tomato flesh, allowed a better description of the relaxation curve for the samples studied than the power law or stretched exponential traditionally used. Moreover, the total relaxation time (τm) given by the generalized Maxwell model showed good correlation with the total gel content of the samples studied.