植物甾醇C_(24)的绝对构型

自然界中存在一系列的甾醇类化合物,在C_(24)上具取代基,例如麦角甾醇(ergosterol,Ⅰ)及菜子甾醇(campesterol,Ⅱ)等为甲基衍生物;大豆甾醇(stigmasterol,Ⅲ)、β-麦胚甾醇(β-sitoscefol,Ⅳ)及γ-麦胚甾醇(γ-sitosterol,Ⅴ)等为乙基衍生物,因而形成一不对称碳中心。由于该碳原子与分子中的其他不对称碳原子距离较远,因此在构型上不易与后者相互联系,所以C_(24)的相对和绝对构型的测定乃成为独立的研究裸题。根据氧化降解反应,从麦角甾醇及菜子甾醇的衍生物可以分别制得左旋及右旋的5,6-二甲基-庚酮-2的缩氨脲衍生物;从大豆甾醇(或β-麦胚甾醇)及γ-麦胚甾醇氧化     

植物甾醇侧链的立体化学——合成24-异-β-麦胚甾醇的试探

本文以C_(20)构型已知的猪去羟胆酸为原料,合成胆固醇的C_(24)-乙基衍生物,企图获得C_(24)异β-麦胚甾醇,以与γ-麦胚甾酵进行比较,从而确定后者的C_(20)的构型.但结果只获得β-麦胚甾醇.     

γ-麦胚甾醇的C_(24)的绝对构型

γ-麦胚甾醇(γ-sitosterol)是大豆甾醇的祖分之一,它的结构曾经从降解法测定为(I),其中C_(24)的超对构型是根据氧化降解产物的分子旋光比较推定的。我们企图从化学方法直接测定γ-麦胚甾醇的C_(24)的绝对构型,曾经进行了一些工作。最近有关     

基于不同萃取剂的生物油常压蒸馏研究

选用乙酸乙酯、二氯甲烷、乙醚和甲苯四种溶剂,分别与生物油按一定质量比混合萃取。将萃取相蒸馏得到的四种油相层与原始生物油进行对比,研究不同萃取剂对生物油萃取-蒸馏后各馏分的产率、水分及高附加值酚类组分变化的影响。结果表明,经萃取-蒸馏后,生物油残渣比例减少,水分含量降低。在四种溶剂中,甲苯萃取率较低,蒸馏后酚类绝对峰面积较小;乙酸乙酯和乙醚萃取效率较高,但两者萃取相蒸馏后酚类含量低;二氯甲烷萃取酚类能力强,其馏分中愈创木酚及其衍生物相对含量为34.11%,比生物油高出15.52%,富集程度高,更有利于后续进一步提纯愈创木酚及其衍生物等高附加值化学品。     

墨红花超临界二氧化碳香味萃取成分的色谱－质谱法测定

由墨红花提取的精油或油树脂是优质的天然香料，被广泛用于化妆品和食品工业。超临界ＣＯ２萃取墨红花精油，既可保持很好的香气，又能克服传统的有机溶剂萃取时有残余溶剂的缺点。用气相色谱－质谱联用法对超临界ＣＯ２萃取物与石油醚萃取物中的组成进行了分析比较。色谱条件为：ＯＶ－１０１固定相，氦气，０．２ｍｍ×５０ｍ石英毛细管柱，柱温７０℃２ｍｉｎ，然后以５℃／ｍｉｎ程序升温至２５０℃。超临界萃取条件为５０℃，２１ＭＰａ，ＣＯ２流量为１０ｍＬ。发现超临界萃取物中的成分包括了石油醚萃取物中的多数主要香味成分，但对香味影响较小的、分子量较大的烷烃和烯烃的含量较少。超临界二氧化碳萃取物的香气与鲜花相近。     

萃取剂组成和结构对煤直接液化油渣萃取行为的影响

煤直接液化过程会产生约占投煤量30%的煤液化油渣,利用萃取手段可将其中的多环芳烃类物质提取出来,制备高价值的炭材料。本文总结了萃取剂的组成结构对煤液化油渣萃取率及萃取产物性质的影响。含有芳环结构或氮氧杂环的萃取剂萃取率可达50%以上。烷烃类有机萃取剂的萃取物主要包含2–4环缩合芳香结构,拥有较低的分子量和杂原子含量。含杂原子有机萃取剂的萃取物主要包含4–7环缩合芳香结构,其分子量大且富含氮、氧、硫等杂原子,C/H原子比较高。吡啶基离子液体萃取物的C/H原子比和芳香度较高;有机酸根基离子液体萃取物的灰分含量较低。使用煤液化油或煤焦油馏分油为萃取剂时,萃取率可达60%,具有工业化应用的前景。     

吡啶萃取对烟煤热解过程焦油生成特性的影响

煤中含有以非共价键结合的可萃取物，煤的萃取物和萃余物热解反应性不同。本研究首先用醋酸消除煤中静电作用力，再以吡啶萃取消除氢键作用力，通过热重和固定床研究了煤萃取物和萃余物的热解特性。相对于原煤，萃取物（E1）的H/C原子比较高，而萃余物（R1）比原煤的孔径有所增大。热重实验表明，萃取物热分解温度低，失重率大；萃余物在485℃之前失重大于原煤，温度高于485℃小于原煤。固定床氮气热解表明，萃取物（E1）的焦油产率和气体比原煤高；萃余物（R1）的焦油产率低于原煤焦油产率。而氢气气氛下，萃取残渣的焦油产率明显高于原煤，这是由于吡啶萃余物具有更开放的孔结构，有利于加氢热解过程氢向孔内扩散，减少了缩聚反应。     

南瓜子油的气相色谱-质谱分析

黑龙江产白皮南瓜子油脂含量约为27％，从提取的南瓜子油中检测出大量的共轭亚油酸、磷脂、角鲨烯、环烷烃、共轭不饱和醛酮、植物甾醇等化学成分，其中植物甾酵的含量约占南瓜子油的1％，能确定结构的甾醇有6种。     

褐煤亚临界—超临界水萃取研究

在半连续实验装置上，采用非等温实验技术，以水为溶剂，对大雁、昌宁两种褐煤进行了萃取。结果表明，在适宜条件下可得到高的转化率和较高的萃取物产率；萃取物中 主要馏分为预沥青烯，为原煤中的富氢组分；过程中产生的气体主要分为CO2；萃取物和气体生成速率随温度而变，在400℃左右存在极大值；萃取后褐煤（即残渣）具有比原煤低的水分、低氧含量、高的碳含量及一定的挥发分。本文对对萃取过程进行了宏观动力学处理，结果表明，萃取过程要用一级反应方程式来描述；在萃取的主要温度区间，活化能约为120kJ/mol.     

墨红花超临界二氧化碳香味萃取成分的色谱－质谱法测定

 由墨红花提取的精油或油树脂是优质的天然香料，被广泛用于化妆品和食品工业。超临界ＣＯ２萃取墨红花精油，既可保持很好的香气，又能克服传统的有机溶剂萃取时有残余溶剂的缺点。用气相色谱－质谱联用法对超临界ＣＯ２萃取物与石油醚萃取物中的组成进行了分析比较。色谱条件为：ＯＶ－１０１固定相，氦气，０．２ｍｍ×５０ｍ石英毛细管柱，柱温７０℃２ｍｉｎ，然后以５℃／ｍｉｎ程序升温至２５０℃。超临界萃取条件为５０℃，２１ＭＰａ，ＣＯ２流量为１０ｍＬ。     

超临界CO_2萃取小麦胚芽油溶解度特性的研究

本文研究了小麦胚芽油在超临界CO_2中的平衡溶解度随介质温度和压力的变化规律,并对超临界CO_2条件下,小麦胚芽中油溶解特性进行了考察。结果表明,小麦胚芽油的恒温溶解度随压力升高而升高,恒压溶解度随温度升高而降低,且溶解过程为放热过程。     

Characterization of <Emphasis Type="Italic">Opuntia ficus indica</Emphasis> seed oil from Tunisia

The lipid fraction of Opuntia ficus indica seeds was extracted and analyzed for its chemical and physical properties such as acid value, free fatty acid percentage (% FFA), iodine index, peroxide value, and saponification value as well as refractive index and density. The yield of seed oil was calculated as 11.75%. The acid and free fatty acid values indicated that the oil has a fairly low acidity. The triacylglycerols, fatty acids, sterols, and tocopherols were identified and their concentrations determined. The main TAGs were LLL (25.60%), OLL (21.53%), PLL (15.53%), and POL + SLL (12.73%). Linoleic acid (60.69%) was the dominant fatty acid, followed by oleic (21.42%) and palmitic (12.76%) acids, respectively. A high level of sterols making up 16.06 g/kg seed oil was present. The sterol marker, β-sitosterol, accounted for 71.60% of the total sterol content in the seed oil. Among the tocopherols present in the oil, γ-tocopherol (421.08 mg/kg) was the main constituent.     

Macroporous chitin affinity membranes for wheat germ agglutinin purification from wheat germ

Macroporous chitin membranes of controlled porosity and pore sizes have been prepared. They have good mechanical properties and allow high flow rates of protein solutions at low pressure drops. Because of the numerous N-acetyl-D-glucosamine (GlcNAc) moieties they contain, the chitin membranes can be used for the separation of some valuable proteins both as affinity ligands and support matrix, without further modification. Due to their high porosity and high adsorption surface area, the chitin membranes provide a larger number of accessible binding sites for the wheat germ agglutinin than the chitin beads do. The adsorption capacity for wheat germ agglutinin (180 mg/g chitin membrane) is about 20 times larger than that of chitin beads. Because of the numerous binding sites, multiple-point bindings are involved in the protein adsorption. For this reason, a strong eluant, namely a 1 M acetic acid aqueous solution, had to be used to efficiently recover the wheat germ agglutinin from the membrane. The wheat germ agglutinin was extracted from wheat germ with 0.05 M HCl, precipitated with ammonium sulfate, dialyzed against 0.01 M Tris–HCl buffer (pH 8.5), and purified on the chitin membrane. A high purity (>99%) wheat germ agglutinin with high yield (∼50 mg/100 g wheat germ) was obtained.     

Enrichment of tocopherols in wheat germ by directly coupled supercritical fluid extraction with semipreparative supercritical fluid chromatography

Enrichment of tocopherol by coupled supercritical fluid extraction/preparative supercritical fluid chromatography is described. Wheat germ powder is used as the starting material and is subjected to supercritical fluid extraction with carbon dioxide. The extracted oil containing tocopherols is concentrated and trapped on a silica gel column by reducing the pressure of carbon dioxide. The trapped oil is then eluted and separated on a silica gel column of 20 mm i.d. x 20 mm length. The column effluent is fractionated by monitoring UV absorption at 290 nm. With this method, tocopherol content of the wheat germ is enriched 100-fold.     

Quantification of the ratio of positional isomer dilinoleoyl-oleoyl glycerols in vegetable oils

The distribution of fatty acids in a triacylglycerol is of great importance from nutritional, biochemical, quality and technological points of view. The ratio of triacylglycerol positional isomers containing two linoleic acid (18:2) and one oleic acid (18:1) moieties--namely, 1(3),2-dilinoleoyl-3(1)-oleoyl glycerol (LLO) and 1,3-dilinoleoyl-2-oleoyl glycerol (LOL)--were quantified in grape seed, olive, pumpkin seed, soybean, sunflower and wheat germ oils by high-performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry (HPLC/APCI-MS) in selected ion monitoring (SIM) mode. Relative LOL contents (LOL/(LLO+LOL)) of the oils were calculated from the mass abundances of the [LL]+ and [LO]+ diacylglycerol fragment ions ([M+H-RCOOH]+) using a calibration curve. The calibration curve of the relative diacylglycerol mass abundances was measured in SIM mode. The relative LOL contents were found to be relatively consistent for each oil variety. The relative LOL content in grape seed, sunflower, pumpkin seed, soybean and wheat germ oils accounted for 44.2 +/- 2.6, 26.8 +/- 3.2, 16.7 +/- 4.6, 15.9 +/- 2.9 and 13.9 +/- 4.3%, respectively. Only olive oils contained practically 100% of the LLO isomer. These results indicate that the unsaturated fatty acids such as linoleic and oleic acids have 'non-random' distribution patterns in various oils.     

Analysis of free and esterified sterols in fats and oils by flash chromatography, gas chromatography and electrospray tandem mass spectrometry.

A method for the analysis of free and esterified sterols has been developed. Fat or oil samples were separated on solid-phase extraction silica gel columns into a sterol ester fraction, a fraction of triacylglycerols, and a free sterol fraction containing partial acylglycerols and residual triacylglycerols. Sterol esters and acylglycerols of the free sterol fraction were transesterified to methyl esters. The fatty acid methyl esters from sterol ester fraction and the free sterols from sterol ester fraction and free sterol fraction were determined by GLC. Precursor ion electrospray MS-MS of sterol fragment ions of sterol ester fractions were recorded and used for determination of sterol ester proportions in butterfat and vegetable oil samples.     

Differentiation of vegetable oils by mass spectrometry combined with statistical analysis

The main triacylglycerol (TAG) composition of different plant oils (almond, avocado, corn germ, grape seed, linseed, mustard seed, olive, peanut, pumpkin seed, sesame seed, soybean, sunflower, walnut and wheat germ) were analyzed using two different mass spectrometric techniques: HPLC/APCI-MS (high-performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry) and MALDI-TOFMS (matrix-assisted laser desorption/ionization time-of-flight mass spectrometry).Linear discriminant analysis (LDA) as a multivariate mathematical statistical method was successfully used to distinguish different plant oils based on their relative TAG composition. With LDA analysis of either APCI-MS or MALDI-MS data, the classification among the almond, avocado, grape seed, linseed, mustard seed, olive, sesame seed and soybean oil samples was 100% correct. In both cases only 6 different oil samples from a total of 73 were not classified correctly.     

Generation of a dynamic combinatorial library using sialic acid aldolase and in situ screening against wheat germ agglutinin

This paper describes the generation of a dynamic combinatorial library of sialic acid analogues using sialic acid aldolase. Addition of wheat germ agglutinin to the equilibrating libraries results in selective amplification of one or more members.     

Analysis of free and esterified sterols in vegetable oil methyl esters by capillary GC

The introduction of quality standards for vegetable oil methyl esters is gaining in importance due to their increased use as diesel fuel substitutes and as technical products. Free and esterified sterols, the main constituents of the unsaponifiable matter in vegetable oils, are recovered in vegetable oil methyl esters and may influence the technical properties of vegetable oil methyl ester products. A rapid gas chromatographic method for the qualitative and quantitative determination of free and esterified sterols in vegetable oil methyl esters has therefore been developed. The concentration of the free sterols as well as their qualitative and quantitative composition and the concentration of the sterol esters have been determined in rape seed oil methyl ester samples by GC–FID. Prior to analysis, the free sterols were silylated with N,O-bis(trimethylsilyl)trifluoroacetamide with 1% of trimethylchlorosilane; betulinol was used as an internal standard. Calibration was performed by analysis of standard solutions containing β-sitosterol, cholesteryl stearate, and betulinol. The reproducibility of the quantitative results has been evaluated by repeated injections of the same test solution and by repeated complete analysis of the same sample.     

Experimental Evaluation of the Additive Compounds Performance on Asphaltene Precipitation Using Automatic Titration Method

The use of soluble amphiphiles oil types provide the most practical and economical solution for crude oil treatment in order to control the asphaltene precipitation phenomenon. In this article, the inhibition performance of a number of new chemical additives to asphaltene precipitation is examined on two types of Iranian crude oil. An automatic titration method is used in experimental evaluation. The vegetable oil types (hazelnut, wheat germ, and walnut), organic acids (oleic and linoleic) and chemical additives (4-dodecylresorcinol and benzyl alcohol) displayed the highest capacity to inhibit asphaltene precipitation. A remarkable onset displacement is displayed by dodecyl resorcinol. The results also revealed that the vegetable oil have high potential in delaying asphaltene precipitation.