植物甾醇单体分离工艺研究进展

该文介绍以精制混合植物甾醇为原料分离甾醇单体工艺,主要是溶剂结晶法富集豆甾醇或谷 甾醇的研究进展情况。     

Seasonal variations in the seed oil ofThevetia peruviana (Pers.) K. Schum

The fixed oil ofThevetia peruviana (Pers.) K. Schum. (T. neriifolia Juss) was obtained by solvent extraction, and its yield and composition were studied to reflect the effect of seasonal variations. Ripe and unripe seeds collected in December and February (the dry season) gave average yields of 72 and 52%, v/w, respectively, and those of May and August (the rainy season) gave 56 and 41%, v/w, respectively. Sitosterol was isolated and identified from the unsaponifiable fraction. Oleic, linoleic, stearic and palmitic acids were shown to be present in all the oils, while myristic, lauric, capric and caprylic acids were identified only in the oil from unripe seeds collected in the rainy season. The physical and chemical constants of the oils are given also.     

Side-chain autoxidation of stigmasterol and analysis of a mixture of phytosterol oxidation products by chromatographic and spectroscopic methods

Although the structure of phytosterols is closely related to cholesterol, there is a gap in knowledge concerning the formation and occurrence of oxidation products from phytosterols. The main objective of this study was to isolate and characterize some side-chain oxidation products formed after autoxidation of stigmasterol. Another objective was to highlight the difficulties in the analysis of phytosterol and a mixture of their oxidation products by GC. Pure stigmasterol was oxidized at 120°C for 72 h in an air-ventilated oven. Preparative TLC separated the oxidation products, and the products were characterized with GC-MS and NMR. In addition to the common ring-structure oxidation compounds, three semipolar oxidation products—24-ethylcholest-5,22-dien-3β,25-diol, 24-ethylcholest-5,22-dien-3β,24-diol, and 24-ethyl-5,22-choladien-3β-ol-24-one—were characterized for the first time by TLC, GC-MS, and NMR. Moreover, the results of the analysis of a large number of oxidation products from sitosterol, campesterol, and stigmasterol by capillary column GC indicated that further efforts and optimization are required in this area.     

Production of androstenedione using mutants of Mycobacterium sp

Mycobacterium sp VKM Ac‐1815D strain was able to cleave sterol side chain giving androstenedione (AD) as a major product with a molar yield of 63–68%. Clones having altered resistance to antibacterial agents were selected. After treatment with ethyl methane sulfonate or mitomycin C, mutants were obtained that retained the ability to produce AD from sitosterol with molar yields of 70–75%. A mutant strain able to effectively reduce 3,17‐diketosteroids at C‐17 was selected. The 17β‐hydroxy steroid dehydrogenase activity of its crude extract was twice as high as that found for the parent organism. The approach offers the possibility of obtaining improved and labelled biocatalysts for AD or testosterone production from sterols. © 2002 Society of Chemical Industry     

Characterization of side-chain oxidation products of sitosterol and campesterol by chromatographic and spectroscopic methods

Based on the cholesterol-lowering effects of phytosterols, known since the 1950s, extra phytosterol amounts have been added to certain food products for almost 10 yr. Literature reports on oxidation of phytosterols in general are limited, and data on side-chain oxidation of these compounds are scarce. The aim of this study was to investigate and characterize autoxidation products from a mixture of the two phytosterols sitosterol and campesterol. A commercial mixture of the two sterols was oxidized for 72 h at 120°C in an air-ventilated oven. The oxidation products were separated by preparative TLC and identified and characterized with GC-MS. The following oxidation products were identified from the two phytosterols: 24-methylcholest-5-en-3β,24-diol, 24-methylcholest-5-en-3β,25-diol, 24-methylcholest-4-en-6α-ol-3-one, 24-methylcholest-4-en-6β-ol-3-one, 24-ethylcholest-5-en-3β,24-diol, 24-ethylcholest-5-en-3β, 25-diol, 24-ethylcholest-4-en-6α-ol-3-one, 24-ethylcholest-4-en-6β-ol-3-one. Full-scan mass spectra of these compounds are reported for the first time as their trimethylsilyl-ether derivatives.     

Supercritical carbon dioxide extraction of okra (Hibiscus esculentus L) seeds

Pilot‐scale supercritical fluid extraction of okra seeds was carried out, using carbon dioxide as solvent, at temperatures of 40, 50 and 60 °C and pressures of 150, 300 and 450 bar. Laboratory‐scale Soxhlet extraction of the ground seeds was carried out with ethanol and n‐hexane. The yields of supercritical fluid extraction and n‐hexane Soxhlet extractions were similar. The ethanol Soxhlet extraction gave the highest yield, but the concentrations of β‐sitosterol and tocopherols in this extract were lower than in the supercritical fluid extraction product. The fatty acid profiles of the extracts were determined, and a high unsaturated/saturated ratio was observed. The fatty acid compositions were only slightly different for oils obtained by the different extraction methods. Copyright © 2005 Society of Chemical Industry     

植物甾醇研究进展

该文总结近年来有关植物甾醇研究进展,包括植物甾醇来源、摄取及安全性,植物甾醇结构与理化性质,生物活性及应用,植物甾醇提取、分析方法。     

Microbial conversion of sterol‐containing soybean oil production waste

Soybean extract residue (scum), a waste of soybean oil production, was examined as a raw material for C₁₇‐ketosteroid production. As a model process, its bioconversion to 9α‐hydroxyandrost‐4‐ene‐3,17‐dione (9‐OH‐AD) by Mycobacterium sp VKM Ac‐1817D was studied. The content of transformable sterols (sitosterol, stigmasterol and campesterol) in scum was estimated at ～14%. The bioconversion of scum to 9‐OH‐AD was characterized by a long lag‐period (300–350 h) followed by 9‐OH‐AD accumulation. The microbial or chemical elimination of fatty non‐identified components resulted in sterol‐enriched scum preparations. Effective conversion of these preparations by Mycobacterium sp was demonstrated: 9‐OH‐AD molar yield ～65% was reached at 60 h from the scum preparation containing 10 g dm^?3 transformable sterols. The process productivity was comparable with that for high quality‐sitosterol of wood origin (tall‐oil sitosterol). Copyright © 2004 Society of Chemical Industry