发酵无花果香料的挥发性成分分析

利用微生物发酵无花果开发特色香料,并采用同时蒸馏萃取装置收集挥发性成分并用气相色谱一质谱仪对生物技术制备的无花果香料挥发性成分进行分离和鉴定,经毛细管色谱分离出47种组分,确认了其中的45种成分,并用面积归一化法测定了各种成分的百分含量,其主要成分为：9,12-十八碳二烯酸乙酯(27．34％)、十六酸乙酯(23．99％)、邻苯二甲酸二丁酯(6．18％)、邻苯二甲酸二异丁酯(5．52％)、9,12-十八碳二烯酸甲酯(4．72％)、十六酸甲酯(4．67％)、9,12,15-十八碳三烯酸乙酯(4．48％)、9-十八碳烯酸乙酯(3．80％)、糠醛(2．53％)、9,12,15-十八碳三烯酸甲酯(1．85％)、十八酸乙酯(1．42％)、9-十八碳烯酸甲酯(1．26％)等。     

咖啡酸苯乙酯衍生物抑制红细胞溶血和HL-60细胞增殖活性的构效关系研究

蜂胶中的主要成分咖啡酸苯乙酯作为重要的抗氧化剂和癌预防试剂分子,引起了人们相当的兴趣。为了研究其构效关系,作者通过酰基化反应合成了6个咖啡酸苯乙酯衍生物,即:咖啡酸苯乙酯(caffeic acid phenethyl ester,CAPE)、芥子酸苯乙酯(sinapic acid phenethyl ester,SAPE)、阿魏酸苯乙酯(ferulic acid phenethyl ester,FAPE)、4-羟基肉桂酸苯乙酯(4-hydroxycinnamicacid phenethyl ester,4-HCAPE)、3,5-二羟基肉桂酸苯乙酯(3,5-dihydroxycinnamic acidphenethyl ester,3,5-DHCAPE)和3-羟基肉桂酸苯乙酯(3-hydroxycinnamic acid phenethyl este,3-HCAPE)。以水溶性偶氮引发剂2,2'-偶氮二(2-脒基丙烷)二盐酸盐诱导的红细胞溶血为模型,研究了它们的抗氧化活性。根据实验测得的有效抑制溶血时间,其活性顺序为:CAPE≈4-HCAPE>SAPE>FAPE>3,5-DHCAPE>3-HCAPE。其活性显著...     

Solubility of multi-component biodiesel fuel systems

Solubility of biodiesel fuel components in fossil diesel fuel-methanol-rapeseed oil methyl ester, fossil diesel fuel-ethanol-rapeseed oil methyl ester and fossil diesel fuel-ethanol-rapeseed oil ethyl ester systems was investigated. The solubility of components in the fossil diesel fuel-ethanol-rapeseed oil methyl ester system at 20 degrees C was substantially higher than in the fossil diesel fuel-methanol-rapeseed oil methyl ester system. The solubility of components in the fossil diesel fuel-ethanol-rapeseed oil ethyl ester system was slightly lower than in the fossil diesel fuel-ethanol-rapeseed oil methyl ester mixture. The moisture content of ethanol had a great influence on mixture solubility. With decrease of temperature, the solubility of components in the fossil diesel fuel-ethanol-rapeseed oil methyl ester system decreased.     

Model sclerotization studies. 3. Cuticular enzyme catalyzed oxidation of peptidyl model tyrosine and dopa derivatives

Incubation of N-acetyltyrosine methyl ester with cuticular enzymes, isolated from the wandering stages of Calliphora sp larvae, resulted in the generation of N-acetyldopa methyl ester when the reaction was carried out in the presence of ascorbate which prevented further oxidation of the o-diphenolic product. Enzymatic oxidation of N-acetyldopa methyl ester ultimately generated dehydro N-acetyldopa methyl ester. The identity of enzymatically produced N-acetyldopa methyl ester and dehydro N-acetyldopa methyl ester has been confirmed by comparison of the ultraviolet and infrared spectral and chromatographic properties with those of authentic samples as well as by nuclear magnetic resonance studies. Since N-acetyldopaquinone methyl ester was also converted to dehydro N-acetyldopa methyl ester and tyrosinase was responsible for the oxidation of N-acetyldopa methyl ester, a scheme for the cuticular phenoloxidase catalyzed conversion of N-acetyltyrosine methyl ester to dehydro N-acetyldopa methyl ester involving the intermediary formation of the quinone and the quinone methide is proposed to account for the observed results. The conversion of N-acetyldopa methyl ester to dehydro derivative remarkably resembles the conversion of the sclerotizing precursor, N-acetyldopamine, to dehydro-N-acetyl-dopamine observed in the insect cuticle. Based on these comparative studies, it is proposed that peptidyl dopa derivatives could also serve as the sclerotizing precursors for the sclerotization of the insect cuticle. © 1995 Wiley-Liss, Inc.     

Glutathione monoethyl ester: preparation, uptake by tissues, and conversion to glutathione

Glutathione monoethyl ester (L-gamma-glutamyl-L-cysteinylglycyl ethyl ester), in contrast to glutathione itself, is effectively transported into many types of cells. The ester is converted intracellularly into glutathione. Intraperitoneal injection of 35S-labeled ester into mice was followed by rapid appearance of isotope in the glutathione of liver, kidney, spleen, pancreas, and heart; the glutathione levels of these tissues also increased. Oral administration of the ester to mice also increased cellular glutathione levels. Relatively little extracellular deesterification was found. Transport of glutathione ester into human erythrocytes and intracellular conversion to glutathione was observed. The findings suggest that the glutathione ester will be useful as a radioprotecting agent and in the prevention and treatment of toxicity due to certain foreign compounds and oxygen. The ester may be useful in experimental work on glutathione transport, metabolism, and function, and in related studies on oxygen toxicity, radiation, mutagenesis, and ageing. Methods for the preparation of glutathione monoethyl ester and several related compounds are given.     

Significance of various cholesterol, ester hydrolases in aorta.

This study for the first time has simultaneously assayed three cholesteryl ester hydrolase activities located in the various subcellular fractions (lysosomal, microsomal, and soluble) of the aorta and their significance in aortic cholesteryl ester accumulation during genetic and cholesterol-fed atherosclerosis is assessed. When the enzyme activities in the aorta of age-matched atherosclerosis-susceptible White Carneau and atherosclerosis-resistant Show Racer pigeons were compared, a decrease in microsomal cholesteryl ester hydrolase activity was found during the period of cholesteryl ester accumulation. However, under cholesterol-fed conditions (which further increase cholesteryl ester accumulation), an increase in lysosomal cholesteryl ester hydrolase activity and a decrease in soluble cholesteryl ester hydrolase activity was found. These studies have documented differences in response in specific cholesteryl ester hydrosases of the aorta to genetic and cholesterol-fed atherogenesis and warrant further studies to investigate the effect of hormonal and dietary factors on the activities of these enzymes.     

Modulation of endosomal cholesteryl ester metabolism by membrane cholesterol

Cells acquire cholesterol in part by endocytosis of cholesteryl ester containing lipoproteins. In endosomes and lysosomes cholesteryl ester is hydrolyzed by acidic cholesteryl ester hydrolase producing cholesterol and fatty acids. Under certain pathological conditions, however, such as in atherosclerosis, excessive levels of cholesteryl ester accumulate in lysosomes for reasons that are poorly understood. Here, we have studied endosomal and lysosomal cholesteryl ester metabolism in cultured mouse macrophages and with cell-free extracts. We show that net hydrolysis of cholesteryl ester is coupled to the transfer of cholesterol to membranes. When membrane cholesterol levels are low, absorption of cholesterol effectively drives cholesteryl ester hydrolysis. When cholesterol levels in acceptor membranes approach saturation or when cholesterol export is blocked, cholesterol is re-esterified in endosomes. These results reveal a new facet of cellular cholesterol homeostasis and provide a potential explanation for cholesteryl ester accumulation in lysosomes of atherosclerotic cells.     

Effect of estrogens on the acitivities of cholesteryl ester synthetase and cholesteryl ester hydrolases in pigeon aorta.

This study is the first to report the effect of conjugated equine estrogens on the acitivity of cholesteryl ester synthetase and cholesteryl ester hydrolases in the aorta. In spontaneously atherosclerosis-susceptible White Carneau pigeons, estrogens significantly decreased (P less 0.01) the activity of cholesteryl ester synthetase and increased (P less than 0.01) the cholesteryl ester hydrolase activity in the microsomal fraction of the aorta. There was no effect on the cholesteryl ester hydrolase activity in the supernatant fraction. The inhibition of cholesteryl ester synthesis and the stimulation of cholesteryl ester hydrolase might be responsible for the decreased content of cholesteryl esters noted in pigeon aorta after estrogen treatment.     

Fatty acid composition of seeds of Satureja thymbra and S. cuneifolia

The chemical composition of fatty acid methyl esters (FAMEs) from seeds of S. thymbra and S. cuneifolia were analyzed by GC/MS. 7 FAMEs were identified from the seeds of S. thymbra mainly as 9-octadecenoic acid methyl ester (43.9%), hexadecanoic acid methyl ester (11.4%), 9,12,15-octadecatrienoic acid methyl ester (Z,Z,Z) (30.2%), and octadecanoic acid methyl ester (14.1%), while from the seed of S. cuneifolia 10 FAMEs were obtained with the main components, similar to S. thymbra. These were identified as 9-octadecenoic acid methyl ester (10.1%), hexadecanoic acid methyl ester (methyl palmitate, 34.6%), 9,12,15-octadecatrienoic acid methyl ester (Z,Z,Z) (6.3%) and octadecanoic acid methyl ester (1.8%).     

左旋多巴甲酯在PLGA微球的稳定性研究

目的：考察左旋多巴甲酯在PLGA微球中的稳定性并探讨其稳定方法。方法：利用HPLC的方法考察了左旋多巴甲酯在不同pH值和光照的环境中和微球里的稳定性。结果：左旋多巴甲酯在pH3中稳定,在微球中也可以稳定一周。结论：包封左旋多巴甲酯在PLGA微球中,是一种有效地保护了左旋多巴甲酯在微球中的活性,可以实现长效缓释,是一种可行的方案。     

Biosynthesis of isoprenoid wax ester in Marinobacter hydrocarbonoclasticus DSM 8798: identification and characterization of isoprenoid coenzyme A synthetase and wax ester synthases

Marinobacter hydrocarbonoclasticus DSM 8798 has been reported to synthesize isoprenoid wax ester storage compounds when grown on phytol as the sole carbon source under limiting nitrogen and/or phosphorous conditions. We hypothesized that isoprenoid wax ester synthesis involves (i) activation of an isoprenoid fatty acid by a coenzyme A (CoA) synthetase and (ii) ester bond formation between an isoprenoid alcohol and isoprenoyl-CoA catalyzed, most likely, by an isoprenoid wax ester synthase similar to an acyl wax ester synthase, wax ester synthase/diacylglycerol acyltransferase (WS/DGAT), recently described from Acinetobacter sp. strain ADP1. We used the recently released rough draft genome sequence of a closely related strain, M. aquaeolei VT8, to search for WS/DGAT and acyl-CoA synthetase candidate genes. The sequence information from putative WS/DGAT and acyl-CoA synthetase genes identified in this strain was used to clone homologues from the isoprenoid wax ester synthesizing Marinobacter strain. The activities of the recombinant enzymes were characterized, and two new isoprenoid wax ester synthases capable of synthesizing isoprenoid ester and acyl/isoprenoid hybrid ester in vitro were identified along with an isoprenoid-specific CoA synthetase. One of the Marinobacter wax ester synthases displays several orders of magnitude higher activity toward acyl substrates than any previously characterized acyl-WS and may reflect adaptations to available carbon sources in their environments.     

Purification and control of bovine adrenal cortical cholesterol ester hydrolase and evidence for the activation of the enzyme by a phosphorylation.

A procedure for the purification of cholesterol ester hydrolase from bovine adrenal cortical 105000 x g supernatant is described. Preincubation of a crude enzyme extract with [gamma-32P]ATP followed by purification resulted in the isolation of a phosphorylated preparation of cholesterol ester hydrolase. The phosphorylated cholesterol ester hydrolase appeared to be composed of 4 subunits, each having a molecular weight of 41000 +/- 280, only one of which may be phosphorylated. Preincubation of the crude enzyme preparation with [alpha-32P]ATP followed by purification did not produce a phosphorylated preparation of cholesterol ester hydrolase. Cyclic-AMP-dependent protein kinase, cyclic AMP, ATP and magnesium ions were required for activation of purified cholesterol ester hydrolase in vitro and the time course of activation closely paralleled the time course of phosphorylation of the enzyme. The addition of ATP, cyclic AMP and magnesium ions to the bovine adrenal cortical 105000 x g supernatant produced a 2.5-fold stimulation in cholesterol ester hydrolase activity. This stimulation was abolished if protein kinase inhibitor was added prior to the addition of ATP cyclic AMP and magensium ions. The addition of magnesium ions or calcium ions to a crude preparation of cholesterol ester hydrolase was found to inhibit activity; however the same additions made to a purified preparation of cholesterol ester hydrolase were not inhibitory. The decrease in cholesterol ester hydrolase activity on incubation with magnesium ion was accompanied by a loss of 32P radioactivity from the protein. Preincubation of a crude preparation of cholesterol ester hydrolase with alkaline phosphatase resulted in a deactivation of cholesterol ester hydrolase. It is suggested that bovine adrenal cortex cholesterol ester hydrolase is activated by a phosphorylation catalysed by a cyclic-AMP-dependent protein kinase. Deactivation of cholesterol ester hydrolase is accomplished by dephosphorylation catalysed by a phosphoprotein phosphatase, dependent on magnesium or calcium ions.     

Selective inhibition of the insulin-stimulated phosphorylation of the 95,000 dalton subunit of the insulin receptor by TAME or BAEE

Added N alpha-p-tosyl-l-arginine methyl ester or N alpha-benzoyl-l-arginine ethyl ester inhibited the stimulation by insulin of phosphorylation of the 95,000 dalton subunit of the insulin receptor both in a partially purified insulin receptor fraction from rat adipocytes and in a highly purified insulin receptor preparation from human placenta. N-alpha-p-tosyl-l-lysine chloromethyl ketone, N alpha-p-tosyl-l-lysine methyl ester, or N-acetyl-l-phenylalanine ethyl ester were much less potent, while N-benzoyl-1-alanine methyl ester was without effect. Inhibition of the phosphorylation by the arginine analogues did not require preincubation of the insulin receptor with inhibitors in the presence of insulin prior to phosphorylation. Inhibition by N alpha-p-tosyl-l-arginine methyl ester was decreased by preincubation of the receptor fraction with cold ATP and MnCl2. These results suggest that N alpha-p-tosyl-l-arginine methyl ester inhibits an initial ATP and Mn2+ dependent reaction in insulin-stimulated phosphorylation process.     

Studies on the chemical stability of propylene glycol alginate esters

The chemical stability of propylene glycol alginates (PGAs) has been examined. Under acidic conditions the ester groups in PGA are stable to hydrolysis but hydrolytic degradation of the glycosidic linkages in the polysaccharide backbone occurs. Under alkaline conditions the ester groups are hydrolysed with the primary 2-hydroxyprop-1-yl ester groups being more susceptible than secondary 1-hydroxyprop-2-yl ester groups, with little degradation of the polysaccharide backbone. Sodium carbonate-bicarbonate buffer was a much more effective hydrolysing reagent than sodium hydroxide at the same concentration and pH, and the rate of hydrolysis was greatly accelerated by increasing the hydrolysis temperature. Acetate, citrate and phosphate ions accelerated the rate of hydrolysis of the ester groups in PGA when added to the sodium hydroxide hydrolysing reagent. Hydrolysis of the ester groups in PGA with sodium hydroxide was unaffected by the addition of imidazole. However hydrolysis of the ester groups in PGA with sodium hydroxide in the presence of 1-aminobutane led to the formation of an alginate amide in which only the primary 2-hydroxylprop-1-yl ester groups were present, suggesting that a nucleophilic substitution of primary ester groups by amine groups is involved in the reaction.     

Pyrimidine nucleoside analogues.X. 5-Substituted 1-(1,3-dihydroxypropyl-2) uracils.

A convenient method is suggested for synthesis of uracil-1-malonic acid diethyl ester by alkylating 2,4-bis(trimethylsilyl) uracil with bromo-malonic acid diethyl ester. This compound has been shown to hydrolyze with NaOH yielding either uracil or uracil-1-acetic acid, depending on reaction conditions. Similarly, thymine-1-malinic acid diethyl ester and 5-fluorouracil-1,3-dimalonic acid tetraethyl ester were obtained. 1-(1,3-Dihydroxypropyl)uracil has been obtained by reducing uracil-1-malonic acid diethyl ester with NaBH4.     

Facilitated transfer of cholesteryl ester between rough and smooth microsomal membranes by plasma lipid transfer protein

The accessibility of intracellular membrane cholesteryl esters to removal was tested with plasma lipid transfer protein as a tool. Incubation of a mixture of non-radioactive smooth microsomes + rough microsomes prelabeled with cholesteryl ester resulted in slight movement (2-4%) of radioactive cholesteryl ester into smooth microsomes. With the addition of increasing amounts of plasma lipid transfer protein to the mixture, the % transfer of cholesteryl ester into smooth microsomes progressively increased until a plateau was reached at 14%. Movement of cholesteryl ester in the reverse direction was examined with non-radioactive rough microsomes as an acceptor and smooth microsomes prelabeled with cholesteryl ester as a donor. The pattern of the % cholesteryl ester transferred in the reverse and forward direction was almost identical in the presence of plasma lipid transfer protein, showing bidirectional movement of cholesteryl ester between membranes.     

Regulation of the uptake of high-density lipoprotein-originated cholesteryl ester by HepG2 cells: role of low-density lipoprotein and plasma lipid transfer protein.

Cholesteryl ester uptake by the human hepatoma cell line HepG2 was studied in vitro by using radiolabeled cholesteryl ester as a tracer. After the cells were incubated in a lipoprotein deficient condition, the rate of radio labeled cholesteryl ester uptake from low-density lipoprotein (LDL) was estimated to be some 25-times higher than that from high-density lipoprotein (HDL). LDL-cholesteryl ester uptake was suppressed by preincubation of the cells with LDL, but pretreatment of the cells with HDL did not show significant effect. HDL-cholesteryl ester uptake was only slightly suppressed by pretreatment of the cells with LDL, and there was no effect with HDL pretreatment. HDL-cholesteryl ester uptake was not affected either by the presence of LDL or human plasma lipid transfer protein alone in the medium under our experimental conditions. Lipid transfer protein enhanced the uptake of radiolabeled cholesteryl ester originating from HDL by the cells only in the presence of LDL. Thus, lipid transfer protein catalyzes a bypass to LDL for the uptake by HepG2 cells of cholesteryl ester molecules which originate in HDL, and this pathway is much more efficient than direct uptake of cholesteryl ester originating in HDL by these cells.     

Cholesteryl ester transfer protein and atherosclerosis

Plasma cholesteryl ester transfer protein facilitates the transfer of cholesteryl ester from HDL to apolipoprotein B-containing lipoproteins. Its significance in atherosclerosis has been debated in studies of human population genetics and transgenic mice. The current review will focus on human plasma cholesteryl ester transfer protein research, including TaqIB, 1405V, and D442G polymorphisms. Plasma cholesteryl ester transfer protein has a dual effect on atherosclerosis, depending on the metabolic background. In hypercholesterolaemia or combined hyperlipidaemia, plasma cholesteryl ester transfer protein may be pro-atherogenic and could be a therapeutic target.     

Synthesis of ester-linked lithocholic acid dimers

Four lithocholic acid dimers were synthesised via esterification. The ester-linked dimer, 3-oxo-5beta-cholan-24-oic acid (cholan-24-oic acid methyl ester)-3-yl ester, (3alpha,5beta), was obtained by condensation of methyl lithocholate with 3-oxo-5beta-cholan-24-oic acid. Borohydride reduction of this ester-linked dimer gave 3alpha-hydroxy-5beta-cholan-24-oic acid (cholan-24-oic acid methyl ester)-3-yl ester, (3alpha,5beta), which was acetylated to 3alpha-acetoxy-5beta-cholan-24-oic acid (cholan-24-oic acid methyl ester)-3-yl ester, (3alpha,5beta). Reaction of methyl lithocholate with oxalyl chloride yielded the oxalate dimer, bis(5beta-cholan-24-oic acid methyl ester)-3alpha-yl oxalate.     

Carboxyl ester lipase cofractionates with scavenger receptor BI in hepatocyte lipid rafts and enhances selective uptake and hydrolysis of cholesteryl esters from HDL3

Cholesteryl esters are selectively removed from high density lipoproteins by hepatocytes and steroidogenic cells through a process mediated by scavenger receptor BI. In the liver this cholesterol is secreted into bile, primarily as free cholesterol. Previous work showed that carboxyl ester lipase enhanced selective uptake of cholesteryl ether from high density lipoprotein by an unknown mechanism. Experiments were performed to determine whether carboxyl ester lipase plays a role in scavenger receptor BI-mediated selective uptake. When added to cultures of HepG2 cells, carboxyl ester lipase cofractionated with scavenger receptor BI and [(3)H]cholesteryl ether-labeled high density lipoprotein in lipid raft fractions of cell homogenates. Confocal microscopy of immunostained carboxyl ester lipase and scavenger receptor BI showed a close association of these proteins in HepG2 cells. The enzyme and receptor also cofractionated from homogenates of mouse liver using two different fractionation methods. Antibodies that block scavenger receptor BI function prevented carboxyl ester lipase stimulation of selective uptake in primary hepatocytes from carboxyl ester lipase knockout mice. Heparin blockage of cell-surface proteoglycans also prevented carboxyl ester lipase stimulation of cholesteryl ester uptake by HepG2 cells. Inhibition of carboxyl ester lipase activity in HepG2 cells reduced hydrolysis of high density lipoprotein-cholesteryl esters approximately 40%. In vivo, hydrolysis was similarly reduced in lipid rafts from the livers of carboxyl ester lipase-null mice compared with control animals. Primary hepatocytes from these mice yielded similar results. The data suggest that carboxyl ester lipase plays a physiological role in hepatic selective uptake and metabolism of high density lipoprotein cholesteryl esters by direct and indirect interactions with the scavenger receptor BI pathway.