不同地区花生品种VE、植物甾醇组成与含量的分析比较

为了明确山东、广东、河南3个地区花生品种VE、植物甾醇组成及含量的差异,采用高效液相色谱法对上述3个地区共45个花生品种中VE、植物甾醇的组成及含量进行分析测定。研究表明:3个地区花生品种中均含有α-、γ-、δ-VE 3种VE异构体和菜油甾醇、豆甾醇、β-谷甾醇3种植物甾醇。总VE含量排序为河南>广东>山东,α-VE含量排序为广东>河南>山东,γ-、δ-VE含量排序均为河南>山东>广东。总甾醇、菜油甾醇、豆甾醇、β-谷甾醇含量排序均为河南>山东>广东。同时,所有花生品种的3种VE异构体中均以α-VE含量最高,占总VE含量的70.37%～78.27%,3种植物甾醇中均以β-谷甾醇含量最高,占花生中植物甾醇总量的61.98%～71.65%。     

溶剂结晶法分离精制豆甾醇工艺对比

通过对溶剂结晶法分离精制豆甾醇工艺进行对比分析,得出工艺简单、适合工业化生产工艺路线。介绍国内外溶剂结晶法（多级分步结晶法、极性溶剂结晶法、有机溶剂结晶法）分离精制豆甾醇的工艺方法并进行对比,可知有机溶剂结晶法中的重结晶法工艺比较简单,非常适合工业化生产。     

降胆固醇方法研究进展

本文简单介绍了能够降低食品和人体血清中的胆固醇含量的几种方法,并对各种研究的进展情况和应用前景进行了简要概述。     

The detection of the presence of hazelnut oil in olive oil by free and esterified sterols

Genuine olive and hazelnut oils from diverse geographical origins, as single varieties and blends, were mixed at different percentages and analysed by the method based on the quantification of free and esterified sterols. Two formulas based on three sterols (Campesterol, Δ⁷-stigmastenol and Δ⁷-avenasterol) together with empirical decision rules were able to detect the presence of hazelnut oil in olive oil when the percentage of the former was more than 6–8%, although this figure was much lower in the most of the adulterations. Results of univariate and multivariate statistical procedures based on the analysis of 116 samples are presented in support of the method efficiency.     

Determination of sterols by capillary column gas chromatography. Differentiation among different types of olive oil: Virgin,refined, and solvent-extracted

Compositional analysis of the sterol fraction of olive oil can be used to assess the degree of purity of the oil and the absence of admixture with other plant oils. This determination also permits characterization of the type of olive oil in question: virgin, refined, or solvent-extracted. In the present work, 130 samples of olive oil were analyzed, the sterol fractions were separated from the unsaponifiable fraction by silica gel plate chromatography, and later they were analyzed as the trimethylsilyl ether derivatives by capillary column gas chromatography. From the results obtained, it was concluded that this methodology is able to differentiate among virgin, refined, and solvent-extracted olive oils. Stigmasterol, clerosterol, Δ5-avenasterol, Δ7-stigmasterol, and Δ7-avenasterol permit the differentiation of the three types of oil from one another. Campesterol, Δ5, 23-stigmastadienol, β-sitosterol, and Δ5,24-stigmastadienol permit the differentiation of only two oils from each other but confirm the conclusions obtained for other sterols. Correlations between the different sterols of virgin, refined, and solven-extracted olive oil also have been obtained.     

Near-Stoichiometric interaction between the non-specific lipid-transfer protein of the yeast Candida tropicalis and peroxisomal acyl-coenzyme A oxidase prevents the thermal denaturation of the enzyme in vitro

A 14-kDa peroxisomal-matrix protein, named PXP-18, of the yeast Candida tropicalis is a structural and functional homologue of the mammalian nonspecific lipid-transfer protein (identical to sterol carrier protein-2). PXP-18 protected acyl-coenzyme A oxidase (ACO), the rate limiting enzyme of the peroxisomal β-oxidation of fatty acids, from thermal inactivation at 48°C or 70°C. This effect was dose-dependent and not replaceable either by chicken egg white lysozyme, which is similar to PXP-18 (insofar as it is basic, small, and monomeric), or by bovine serum albumin, a carrier of lipids in the blood. ACO was irreversibly denatured by heat treatment at 70°C for 15 min. However, when ACO and PXP-18 were similarly heat-treated, they formed a large complex at a molar ratio of PXP-18 to ACO subunit that was about one, independent of their initial ratio. This near-stoichiometric complex had ACO activity after a 500-fold dilution and was accompanied by ACO that was free of PXP-18 and indistinguishable from native ACO in size and activity. PXP-18 also protected urate oxidase, another peroxisomal enzyme, from inactivation at 66°C for 15 min and facilitated the renaturation of ACO denatured by 2 M urea. These results indicated that PXP-18 is active in modulating the structure of peroxisomal enzymes in vitro. It is possible that PXP-18 functions as a stress protein or as a part of the system that keeps peroxisomal proteins intact.     

Predominant localization of non-specific lipid-transfer protein of the yeast Candida tropicalis in the matrix of peroxisomes

PXP-18 is a 14-kDa major peroxisomal protein of the yeast Candida tropicalis and a homologue of the non-specific lipid-transfer protein (nsLTP) of mammals. Mammalian nsLTP is thought to facilitate the contact of membranes, to stimulate lipid-transfer between them. If PXP-18 functions like nsLTP, it must be present on organelle membranes. Immunoelectron microscopy of C. tropicalis cells indicated that gold particles, which visualized PXP-18, localized exclusively in the matrix of peroxisomes. Subcellular fractionation followed by Western blotting revealed the association of PXP-18 with peroxisomes in C. tropicalis cells. An enzyme-linked immunosorbent assay revealed that almost all the PXP-18 associated with peroxisomes was detectable after the solubilization of the organelle but not before, implying the predominance of PXP-18 inside peroxisomes. This differential assay was applied to the intracellular import of the intact and truncated PXP-18s expressed in Saccharomyces cerevisiae cells. Most of the intact PXP-18 was shown to be imported into the matrix of host-cell peroxisomes, whereas the truncated PXP-18, which lacked the C-terminal tripeptide Pro-Lys-Leu, no longer targeted peroxisomes. These results are consistent with the view that PXP-18 is the matrix protein of peroxisomes and must function in a system other than that of lipid transfer.     

二甲双胍调节AMPK/SREBP-1通路及在临床中的应用进展

二甲双胍是临床上常用的降糖药物之一,除了降血糖外,还有多种医学生物价值在不断被发现而备受关注。近年研究表明,二甲双胍通过激活AMPK抑制固醇调节元件结合蛋白-1（SREBP-1）减少脂质合成,在治疗肝脏脂肪变性、改善胰岛素敏感性、预防动脉粥样硬化和心血管功能障碍、肿瘤、多囊卵巢综合征以及新型冠状病毒肺炎的辅助治疗等方面发挥一定作用。因此,本文就二甲双胍通过激活AMPK抑制SREBP-1调控糖脂质代谢的可能机制以及在临床中的应用做一综述。     

STEROL BIOSYNTHESIS BY STRAINS OF SACCHAROMYCES CEREVISIAE IN THE PRESENCE AND ABSENCE OF DISSOLVED OXYGEN

The content of sterols in Saccharomyces cerevisiae which has been harvested after anaerobic growth and then added to a complex nutrient medium, rises rapidly from ca. 1 mg/g dry yeast to ca. 10 mg in the presence of dissolved oxygen. A range of sterols, present principally as sterol esters, is formed during this period. The concentration of free sterols does not rise above 3 mg/g and esters are thought to form a reserve sterol pool. Cyclization of squalene to lanosterol in the presence of oxygen seems not to be markedly affected by oxygen concentration in contrast to demethylation and desaturation reactions on the pathway to ergosterol. When oxygen concentration falls to zero, further metabolism of preformed sterols continues, with the accumulation of episterol and ergosterol and reduction in the concentration of zymosterol and 24(28)-dehydroergosterol. During anaerobic growth a marked hydrolysis of sterol esters occurs and free sterols eventually predominate.