The number of characterized phytosterol oxidation products (POPs) from both ring- and side-chain structures has increased during recent decades, resulting in difficulties in the separation of POPs on different gas chromatography (GC) capillary columns. The main objective of this study was to separate a mixture of 29 purified and characterized oxidation products from sito-, campe- and stigmasterol using GC capillary columns with different polarity. For the first time in the area of POPs analysis, the separation efficiency of the combination of two capillary GC columns with different polarities was investigated. A non-polar 5% phenyl coated (DB5-MS) and a mid-polar 35% phenyl coated (DB35-MS) column was combined with a pressfit connector. The main improvement was enhanced base line separation for many of the analyzed POPs, compared with the separations achieved using the individual columns. However, three pairs of POPs co-eluted: 24-hydroxysitosterol/campesterol-5beta,6beta-epoxide, stigmasterol-5beta,6beta-epoxide/campesterol-5alpha,6alpha-epoxide and stigmasterol-5alpha,6alpha-epoxide/campestanetriol. 相似文献
Metathesis reactions of Δ22-steroids are studied. The cross metathesis reactions of model Δ22-steroids with excess of simple alkenes are sluggish or do not occur at all. In contrast, derivatives of both trans- and cis-Δ22-cholesterol undergo ring closing metathesis reactions but the former reacts faster. However, the side chain double bond in stigmasterol and ergosterol is too crowded for metathesis reactions promoted by currently available catalysts. 相似文献
The title compound has been synthesized in the reaction of ferrocene with ethoxycarbonyl isocyanate in methanesulfonic acid. It has been found that it undergoes N-alkylation with benzyl alcohols under classical Mitsunobu conditions (PPh3/DEAD). However, in the reaction with cholesterol and stigmasterol O-alkylation with inversion of configuration occurred (confirmed by hydrolysis of the product obtained from cholesterol to epicholesterol). The structure of the product obtained from p-nitrobenzyl alcohol was determined by X-ray diffraction. 相似文献
Cell suspension cultures of Croton stellatopilosus were fed with [1-13C]glucose and [2-13C]sodium acetate and cultured under control conditions. β-Sitosterol and stigmasterol were isolated and their 13C-labeling patterns examined using quantitative NMR spectroscopy. Analysis of the patterns of 13C-enrichment revealed that all the isoprene units in the molecules of both phytosterols originated exclusively from the mevalonate pathway. These results were in contrast with our previous study using callus cultures of C. stellatopilosus, which showed that the isoprene units of β-sitosterol and stigmasterol were supplied equally from both the deoxyxylulose phosphate (DXP) pathway and the mevalonate pathway. Observation by transmission electron microscopy of sub-cellular structures of both cell types revealed that the callus cells contained partially differentiated chloroplasts, whereas the suspension cultured cells did not. Since the DXP pathway is known to be located in the chloroplasts, it was suggested that the presence of chloroplasts is essential for expression of the DXP pathway. Therefore, the sole operation of the phytosterol biosynthesis by the mevalonate pathway observed in this study was likely to be the result of non-expression of the DXP pathway in the chloroplast-free cell suspension cultures of C. stellatopilosus. 相似文献
Leaves of an endemic plant Glyptopetalum calocarpum are used by Nicobarese tribes of Andaman and Nicobar Islands, India, to prepare traditional medicine for treating fever. In the present investigation, pharmacologically active compounds were isolated from this plant and their antimicrobial efficacy was evaluated against the leptospiral strains. The anti-leptospiral activity of six plant-derived compounds was determined by both microdilution and macrodilution methods. Two out of six compounds, namely lupenone and stigmasterol, showed anti-leptospiral activity. The minimum inhibitory concentrations of the two compounds tested against pathogenic leptospiral strains belonging to 10 serovars were in the range of 100–200 μg/mL. The range of minimum bactericidal concentrations was 400–800 μg/mL. Compounds lupenone, stigmasterol, lupeol, β-amyrin and β-amyrin acetate had negligible or no haemolytic activity, exhibiting IC50 values of greater than 5 mg/mL. Further in vivo studies are needed to investigate the pharmacological and toxicological properties of G. calocarpum before it can be considered as a new anti-leptospiral agent. 相似文献
The monolayer behavior of three mixed systems of dipalmitoyl phosphatidyl choline (DPPC) with sterols; cholesterol (Ch), stigmasterol (Stig), and cholestanol (Chsta) formed at the interface of air/water (phosphate buffer solution at 7.4 with addition of NaCl) was investigated in terms of surface pressure (π) and molecular occupation surface area (A) relation. A series of π–A curves at every 0.1 mol fraction of each sterol for the three combinations of mixed systems were obtained at 25.0 °C.
On the basis of the π–A curves, the additivity rule in regard to A versus sterol mole fraction (Xst) was examined at discrete surface pressures such as 5, 10, 15, 20, 25, 30 mN m−1, and then from the obtained A–Xst curves the partial molecular areas (PMA) were determined. The A–Xst relation exhibited a marked negative deviation from ideal mixing in the pressure range below 10 mN m−1, i.e. in the expanded liquid film region (below the transition pressure of DPPC).
The PMA of Ch at π=5 mN m−1, for example, was found to be conspicuously negative in the range of XCh=0–0.2 (about −0.4 nm2 per molecule) and slightly positive (ca. 0.1 nm2 per molecule) in the range XCh=0.2 to 0.4. Above XCh=0.5, Ch’s PMA was almost the same as the surface area of pure Ch, while DPPC’s PMA was reduced to 60% of that of the pure system.
Excess Gibbs energy (ΔG(ex)) as a function of Xst was estimated at different pressures. Applying the regular solution theory to thermodynamic analysis of ΔG(ex), the activity coefficients (f1 and f2) of DPPC and the respective sterols as well as the interaction parameter (Ip) in the mixed film phase were evaluated; the results showed a marked dependence on Xst.
Compressibility Cs and elasticity Cs−1 were also examined. These physical parameters directly reflected the mechanical strength of formed monolayer film.
Phase diagrams plotting the collapse pressure (πc) against Xst were constructed, and the πc versus Xst curves were examined for the respective mixed systems in comparison with the simulated curves of ideal mixing based on the Joos equation.
Comparing the monolayer behavior of the three mixed systems, little remarkable difference was found in regard to various aspects. In common among the three combinations, the mole fraction dependence in monolayer properties was classified into three ranges: 0<Xst<0.2, 0.2<Xst<0.4 and 0.5<Xst<1. How the difference in the chemical structure of the sterols influenced the properties was examined in detail. 相似文献