气相色谱法测定食品中植物甾醇含量研究

目的：建立气相色谱法测定食品中植物甾醇含量的方法。方法：对常见食品中的菜油甾醇、豆甾醇、β-谷甾醇含量进行定性定量分析。食品样品经皂化后提取,浓缩后用正己烷定容,上机测定。结果：本方法可有效分离食品中植物甾醇组分,各组分在0.005~0.2 mg/mL范围内线性关系良好,相关系数R2均在0.99以上;检出限为0.3 mg/100 g,其回收率在84.9%~106.2%,方法的重现性、精密度和稳定性良好,RSD均小于5%。结论：与液相色谱法相比,本方法能够有效分离和测定植物甾醇组分,且具有样品前处理简单、方法重现性好、准确度和灵敏度高等优点,可用于测定食品中植物甾醇组分含量。     

应用气-质联用仪测定三种螺旋藻中的甾醇成分

应用GLC/MS联用仪对室内培养的钝顶螺旋藻(Spirulina platensis (Nordstedt) Geitler)、极大螺旋藻(S.maxima (Stechell & Gardiner) Geitler)和盐泽螺旋藻(S.subsalsa Oerst)的甾醇成分进行了测定。从钝顶螺旋藻和盐泽螺旋藻中共分出11个相同的甾醇组分:胆甾醇、胆甾烷醇、芸苔甾醇、麦角甾醇、海绵甾醇、菜子甾醇、豆甾醇、24-乙基-Δ~(5,7,22)-胆甾醇、β-谷甾醇、异岩藻甾醇和4α,23,24-三甲基Δ~(5,22)-胆甾醇;从极大螺旋藻中只分离出8个甾醇组分。其中胆甾醇含量最高。4α,23,24-三甲基-Δ~(5,22)-胆甾醇为蓝藻中首次报导。     

马尾松花粉中植物甾醇成分分析

采用正己烷超声浸提法提取破壁马尾松花粉中的植物甾醇成分,L-B比色法(Liebermann-Burchard)测定马尾松花粉中总甾醇含量,并用GC-MS(气相色谱-质谱联用法)首次对马尾松花粉中的植物甾醇进行详细定性分析。测得马尾松花粉中总甾醇含量为1.680 mg/g,并鉴定出8种植物甾醇成分,分别为:Δ5-菜油甾醇,豆甾醇,Δ7-菜油甾醇,β-谷甾醇,Δ5-燕麦甾醇,禾本甾醇,环阿屯醇和24-亚甲基环木菠萝烷醇。     

豆甾醇与琥珀酸酐单酯化反应工艺及动力学研究

研究了甲苯为溶剂,吡啶为催化剂,豆甾醇与琥珀酸酐的酯化反应工艺和反应动力学。探讨了反应温度、催化剂吡啶用量、反应物的摩尔配比和反应时间对酯化反应结果的影响。实验结果表明:豆甾醇与琥珀酸酐的反应产物为豆甾醇琥珀酸单酯;当吡啶的体积分数为1.5%,反应物的摩尔比为1.0∶1.6,回流下反应20 h后,豆甾醇的酯化率大于97%,反应后的溶液经蒸发回收溶剂甲苯,固体产物分别经乙醇和水洗涤除杂,所得固体在60℃下真空干燥至恒重,得到的豆甾醇琥珀酸单酯的单程收率大于86%。单酯化反应满足二级不可逆反应动力学规律,反应的活化能为85 kJ/mol。     

植物甾醇在植物逆境胁迫中的研究进展

植物甾醇是一类重要的生理活性物质,对植物的生长发育具有重要作用,对响应植物逆境胁迫也具有重要功能.植物甾醇是细胞膜和脂质筏的重要组分,与膜的稳定性密切相关,主要通过甾醇含量的相对变化维持膜的稳定性及影响脂质筏的生物功能响应逆境胁迫.植物甾醇作为信号分子参与逆境胁迫中的信号传导,油菜素内酯类(BRs)是植物甾醇合成途径的重要产物,作为一种重要的信号分子调控植物甾醇合成酶基因的表达以响应逆境胁迫.     

植物甾醇酯合成研究进展

植物甾醇广泛存在于植物的根、茎、叶、果实和种子中,易受光、热、氧化等作用而被分解,具有生物利用率低、水溶性和脂溶性较差等特点。植物甾醇与脂肪酸酯化生成的植物甾醇酯可以有效降低植物甾醇的氧化率,具有更好的脂溶性和降血清、胆固醇的能力,更易被人体吸收。作为一类新型的功能食品添加剂,植物甾醇酯的市场需求量逐年增长。对植物甾醇酯的原料植物甾醇和脂肪酸来源进行了简单介绍,就近年来国内外植物甾醇酯的合成方法进行了系统阐述,重点介绍了酸/碱化学催化法和脂肪酶催化合成方法,对这两类方法的优缺点分别进行了评价,并对未来研究的重点内容和待突破的核心技术进行了展望。     

亚洲玉米螟对常见植物甾醇代谢利用研究

亚洲玉米螟Ostrinia furndcalis G.在缺少甾醇的饲料上不能正常生长发育,能通过脱烷基化作用将△⁵-植物甾醇,如谷甾醇和豆甾醇脱去支链上的烷基变成胆甾醇加以利用,而对△⁷-烯甾烷醇的代谢则有困难。     

苍耳甾醇物质对菜青虫取食、血淋巴和中肠酶活性及中肠组织的影响

甾醇是植物体内的重要次生物质,具有多种生物活性。为探明植物甾醇类物质对害虫的作用机理,采用叶碟饲喂法进行取食处理后研究了苍耳Xanthium sibiricum中分离纯化的甾醇类组分（甾醇A和甾醇B）对4龄菜青虫Pieris rapae的取食、酶活性以及中肠组织的影响。结果表明： 苍耳甾醇类组分甾醇A和甾醇B能明显抑制菜青虫的取食,拒食中浓度AFC50分别为0.0229 和0.0147 mg/mL;同时,显著降低菜青虫中肠蛋白酶、淀粉酶和羧酸酯酶活性,其中,甾醇B的作用效果较强,处理后24 h和36 h, 对蛋白酶活性抑制率分别为23.74%和58.59%,对中肠羧酸酯酶的活性抑制率分别为49.01%和83.03%;降低血淋巴蛋白质含量,诱导菜青虫血淋巴羧酸酯酶活性的提高;破坏昆虫中肠上皮组织,微杆模糊不清呈消融状,杯状细胞的杯腔基部微绒毛消失。这些结果说明苍耳甾醇类物质对菜青虫的取食抑制可能与对中肠消化酶活性的抑制以及对中肠上皮组织的破坏有关,植物甾醇组分的不同配比影响其对昆虫的作用效果。     

植物体内甾醇的合成和生理作用

植物甾醇属于甾类化合物,以自由状态,与复杂脂类或和某些化合物结合成复合体的形式,存在于高等植物的细胞膜,细胞质和细胞器内,细胞膜内的甾醇和磷脂相互作用能够保持膜结构的稳定和调节细胞膜透性。植物体内甾醇的合成是从乙酰辅酶A（acetyl-CoA)开始,并有其种类特异性和特有的酶催化系统。甾醇参与植物对外界的胁迫反应,因此,获得甾醇突变体植株是抗病虫育种的有效途径。     

高效液相色谱测定血清中的非胆因醇甾醇

本文介绍一种用高效液相色谱同时测定血清中２４－脱氢胆固醇、７－烯胆甾烷醇、菜油甾醇、胆甾烷醇和β－谷甾醇的方法。血清加内标（６－氯豆甾醇）后用氢氧化钾醇溶液皂化,用正已烷提取其中的各种甾醇,将提出的甾醇衍生为苯氨基甲酸酯,用ＨＰＬＣ分离测定。本法样品处理简单,色谱分析时间短,批内和批间变异系数分别为２．２～３．８％和３．３～６．７％。本文也首报告我国成年人血清非胆固醇甾醇水平,５种甾醇血清深度的总     

α-亚麻酸甾醇酯的理化特性及氧化稳定性研究

本文研究了采用无溶剂直接酯化法合成得到的α-亚麻酸甾醇酯的理化特性、脂溶性、结晶特性、油脂氧化稳定性。结果表明,α-亚麻酸甾醇酯具有理想的理化特性,酸价和过氧化值分别为1.2 mg KOH/g和0.56meq/kg,反式脂肪酸含量小于0.1%,在不同植物油脂中的溶解性达到30%以上,结晶温度区间在-25.9～-29.6℃之间。α-亚麻酸甾醇酯在大豆油、油菜籽油和亚麻籽油中的浓度分别小于0.1%、0.1%和0.3%,油脂的氧化诱导时间随浓度增加而增加。因此α-亚麻酸甾醇酯良好的理化特性表明其在不同形态食品、保健品和医药产品等中将具有较广的应用范围,是一种具有较高营养价值的功能性食品添加剂。     

Incorporation of phytosterols in human keratinocytes. Consequences on UVA-induced lipid peroxidation and calcium ionophore-induced prostaglandin release

We have designed experimental conditions allowing the replacement of 50% of cholesterol of human keratinocytes (SVK14 line) with sitosterol or stigmasterol without affecting cellular viability. We have investigated the influence of incorporating phytosterol on the ultraviolet-A-induced formation of lipid-peroxidation products (thiobarbituric reactive substances (TBARS)) in these cells. Our results show that ultraviolet-A-induced lipid peroxidation depends on the nature of the phytosterol. Sitosterol induces a significant decrease (-30%) of TBARS relative to the control whereas stigmasterol markedly increases lipid peroxidation (+70%). We have also studied the effect of plant sterols on prostaglandin release by using the Ca(2+) ionophore A23187 as an in vitro model of the inflammation induced by UVA radiation. We show that in the presence of 50% of phytosterol (particularly stigmasterol), the release of prostaglandin (6-ketoPG(1alpha), PGE(2)) is increased compared to untreated cells. This pro-inflammatory effect of phytosterols is correlated with a loss of the regulation of the intracellular Ca(2+) concentration.     

Impact of dietary sterols on life-history traits of a caterpillar

Although lepidopteran larvae have been shown to metabolise a number of different phytosterols, their life-history traits in response to these different phytosterols may vary with the species. Using the specialist moth, Plutella xylostella (Linaeus) (Lepidoptera), growth, development and fecundity on artificial diets containing host and non-host phytosterols were measured over two generations. Because of the nature of the experimental design, maternal effects linked to dietary sterol could be assessed. In both generations, survival was highest on diets containing sitosterol as the primary phytosterol. A significant decrease in survival on stigmasterol, a non-host phytosterol, was observed between generations. As expected, survival on a control diet with only trace-sterols decreased between generations. Larval duration and pupal duration in both generations was longest on the diets containing the non-host phytosterols, stigmasterol and spinasterol, and on the trace-sterol diet. Finally, fecundity was affected by dietary sterol. In the first generation, fewer viable eggs were produced on the stigmasterol and trace-sterol diets than on wheatgerm control diet. In both generations, dietary sterol significantly influenced percentage egg viability. Overall, these results indicate that differences in phytosterol structure can have pronounced effects on life-history traits, especially when they are projected to the population level. The implications of these results are discussed with respect to phytosterol use by phytophagous insects and their host plant affiliations.     

Sugar availability modulates polyisoprenoid and phytosterol profiles in Arabidopsis thaliana hairy root culture

Sugars are recognized as signaling molecules regulating the biosynthesis of secondary metabolites in plants. Here, a modulatory effect of sugars on dolichol and phytosterol profiles was noted in the hairy roots of Arabidopsis thaliana. Arabidopsis roots contain a complex dolichol mixture comprising three groups (‘families’) of dolichols differing in the chain-length. These dolichols, especially the longest ones are accompanied by considerable amounts of polyprenols of the same length. The spectrum of polyisoprenoid alcohols, i.e. dolichols and polyprenols, was dependent on sugar type (glucose or sucrose) and its concentration in the medium. Among the long-chain dolichols Dol/Pren-20 (dolichol or prenol molecule composed of 20 isoprene residues) and Dol/Pren-23 were the main components at 0.5% and 2% glucose, respectively. Moreover, the ratio of polyprenols versus respective dolichols was also modulated by sugar in this group of polyisoprenoids, with polyprenols dominating at 3% sucrose and dolichols at 2% glucose. Glucose concentration affected the expression level of genes encoding cis-prenyltransferases, enzymes responsible for elongation of the polyisoprenoid chain. The most abundant phytosterols of the A. thaliana roots, β-sitosterol, stigmasterol and campesterol, were accompanied by corresponding stanols and traces of brassicasterol, stigmast-4,22-dien-3-one and stigmast-4-en-3-one. Similar to the polyisoprenoids, sterol profile responded to the sugar present in the medium, β-sitosterol dominating in roots grown on 3% or lower glucose concentrations and stigmasterol in 3% sucrose. These results indicate an involvement of sugar signaling in the regulation of cis-prenyltransferases and phytosterol pathway enzymes.     

Short-step synthesis of chenodiol from stigmasterol

Chenodiol is an important bile acid widely used for gallstone dissolution and cholestatic liver diseases. We succeeded in a short-step synthesis of chenodiol, starting from the safer phytosterol, stigmasterol.     

Short-step Synthesis of Chenodiol from Stigmasterol

Chenodiol is an important bile acid widely used for gallstone dissolution and cholestatic liver diseases. We succeeded in a short-step synthesis of chenodiol, starting from the safer phytosterol, stigmasterol.     

Comparing different sterol containing solid lipid nanoparticles for targeted delivery of quercetin in hepatocellular carcinoma

Quercetin (QT) is a potential chemotherapeutic drug with low solubility that seriously limits its clinical use. The aim of this study was enhancing cellular penetration of QT by sterol containing solid lipid nanoparticles (SLNs) which make bilayers fluent for targeting hepatocellular carcinoma cells. Three variables including sterol type (cholesterol, stigmasterol and stigmastanol), drug and sterol content were studied in a surface response D-optimal design for preparation of QT-SLNs by emulsification solvent evaporation method. The studied responses included particle size, zeta potential, drug loading capacity and 24?h release efficiency (RE₂₄%). Scanning electron and atomic force microscopy were used to study the morphology of QT-SLNs and their thermal behavior was studied by DSC analysis. Cytotoxicity of QT-SLNs was determined by MTT assay on HepG-2 cells and cellular uptake by fluorescence microscopy method. Optimized QT-SLNs obtained from cholesterol and QT with the ratio of 2:1 that showed particle size of 78.0?±?7.0?nm, zeta potential of??22.7?±?1.3?mV, drug loading efficiency of 99.9?±?0.5% and RE₂₄ of 56.3?±?3.4%. IC₅₀ of QT in cholesterol SLNs was about six and two times less than free QT and phytosterol SLNs, respectively, and caused more accumulation of QT in HepG2 cells. Blank phytosterol SLNs were toxic on cells.     

Biosynthesis of beta-sitosterol and stigmasterol in Croton sublyratus proceeds via a mixed origin of isoprene units

A green callus culture of Croton sublyratus Kurz established from the leaf explants appeared to actively synthesize two well-known phytosterols, beta-sitosterol and stigmasterol. The phytosterol biosynthesis was highly active during the linear phase of the culture. Feeding of [1-13C]glucose into the callus culture at this growth phase showed that the label from glucose was highly incorporated into both phytosterols. Isolation of the labeled products followed by 13C NMR analysis revealed that the phytosterols had their 13C-labeling patterns consistent with the acquisition of isoprene units via both the mevalonate pathway and the deoxyxylulose pathway with relatively equal contribution. Since the biosynthesis of phytosterol has so far been reported to be mainly from the classical mevalonate pathway, this study provides a new evidence on the biosynthesis of phytosterols via the novel deoxyxylulose pathway.     

An improved method for the synthesis of 2-arachidonoylglycerol

2-Arachidonoyl glycerol (2-AG) is an endogenous agonist for cannabinoid receptors and has exhibited various biological activities. In this study, we reported an improved method for the synthesis of 2-AG by enzymatic ethanolysis of arachidonic acid-rich oil. The effects of solvent type, addition amounts of solvent and lipase, and reaction time on the content of 2-monoacylglycerols (2-MAGs) in the crude reaction mixture were investigated. Under the optimal conditions, 34.1% (area/area) 2-MAGs were produced in the crude mixture. 2-MAGs were obtained at 98–99% purity and 85.3% 2-MAGs yield (mol/mol) after solvent fractionation to fully remove impurities, including diacylglycerols (DAGs), triacylglycerols (TAGs) and fatty acid ethyl esters. Subsequently, pure 2-MAGs were further purified by crystallization in hexane to remove all saturated and partially unsaturated 2-MAGs to enrich 2-AG. After a two-step purification, 79.4% 2-AG was obtained at 42.9% 2-MAGs yield. Compared to previous methods for the synthesis of 2-AG, the method reported herein is easier to scale, greener, simpler and more economical.     

Phytosterols and lecithin do not have an additive effect in lowering plasma and hepatic cholesterol levels in diet-induced hypercholesterolemic rats

Both plant sterols and lecithin are used as dietary supplements for lowering blood cholesterol in Western countries. This study evaluated the possibility of an additive effect of these ingredients on the regulation of lipid concentrations and cholesterol metabolism. Male Sprague-Dawley rats were randomly divided into three groups, and fed one of the following diets for 5 weeks; high cholesterol diet (HCD), phytosterol mixture-supplemented diet (PD, HCD+0.25% phytosterols), or phytosterol mixture and lecithin-supplemented diet (PLD, PD+0.15% lecithin). Feeding the PD for 5 weeks resulted in a 34% and 41% decrease in plasma total- and VLDL+LDL-cholesterol levels, respectively, and a 23% decrease in hepatic cholesterol content compared to those for the HCD rats (p < 0.05). These cholesterol-lowering properties of the phytosterol mixture were also associated with the down-regulation of hepatic acyl CoA:cholesterol acytransferase (ACAT) activity (p < 0.05). Addition of lecithin plus phytosterol mixture to the hypercholesterolemic diet did not significantly affect blood and hepatic lipid concentrations (with the exception of 36% decrease in hepatic triglyceride level, p < 0.05) as well as hepatic ACAT activity compared to feeding the hypercholesterolemic diet supplemented with phytosterol alone. These results indicate that combining lecithin, at a 0.15% level, with a phytosterol mixture-supplemented diet does not exhibit an additive effect in regulating hepatic ACAT activity or lowering blood cholesterol in hypercholesterolemic rats.