Arylbenzofurans from Dalbergia parviflora

The isolation of two polysubstituted arylbenzofurans from the heartwood of Dalbergia parviflora is described. Their structures were elucidated mainly by spectroscopic techniques (UV, IR, ¹H and ¹³C NMR). They were named parvifuran (5-hydroxy-6-methoxy-3-methyl-2-phenylbenzofuran) and isoparvifuran (5-hydroxy-6-methoxy-2-methyl-3-phenylbenzofuran) and are the first compounds of this class isolated from a Dalbergia species.     

Novel derivatives of chitosan and their antifungal activities in vitro

Three kinds of Schiff bases of carboxymethyl chitosan (CMCTS) were prepared, and their antifungal activities were assessed according to Jasso de Rodríguez's method. The results indicated that 2-(2-hydroxybenzylideneamino)-6-carboxymethylchitosan (HNCMCTS) and 2-(5-chloro-2-hydroxybenzylideneamino)-6-carboxymethylchitosan (HCCMCTS) had better inhibitory effects than those of chitosan or CMCTS against Fusarium oxysporium f. sp. vasinfectum, Alternaria solani, and Valsa mali.     

Membrane-associated reactions in ubiquinone biosynthesis: 2-octaprenyl-3-methyl-5-hydroxy-6-methoxy-1,4-benzoquinone methyltransferase

The O-methylation of 2-octaprenyl-3-methyl-5-hydroxy-6-methoxy-1,4-benzoquinone, which has been previously postulated to be the final reaction in the biosynthesis of ubiquinone was demonstrated in vitro using cell extracts of Escherichia coli. $\text{S-}\text{Adenosyl}\text{-}\text{l}\text{-}\text{methionine}$ was active as the methyl donor for the reaction. The enzyme concerned, S-adenosyl-l-methionine: 2-octaprenyl-3-methyl-5-hydroxy-6-methoxy-1,4-benzoquinone-O- methyltransferase, was partially purified and shown to have a molecular weight of about 50 000 and to require a divalent metal and dithiothreitol for optimal acitivity in vitro. The methyltransferase was absent from extracts from ubiG^? mutants suggesting that the ubiG gene is the structural gene coding for the methyltransferase. The enzyme, although not firmly membrane-bound, showed some affinity for the cell membrane in broken cell preparations and could utilize the benzoquinone substrate when the latter was free or bound to the cell membrane, with about equal efficiency. It is concluded that in vivo, the methyltransferase reaction probably occurs at the internal surface of the cytoplasmic membrane.     

Nature and position of functional group on thiopurine substrates influence activity of xanthine oxidase — Enzymatic reaction pathways of 6-mercaptopurine and 2-mercaptopurine are different

Xanthine oxidase-catalyzed hydroxylation reactions of the anticancer drug 6-mercaptopurine (6-MP) and its analog 2-mercaptopurine (2-MP) as well as 6-thioxanthine (6-TX) and 2-thioxanthine (2-TX) have been studied using UV-spectroscopy, high pressure liquid chromatography, photodiode array, and liquid chromatography-based mass spectral analysis. It is shown that 6-MP and 2-MP are oxidatively hydroxylated through different pathways. Enzymatic hydroxylation of 6-MP forms 6-thiouric acid in two steps involving 6-TX as the intermediate, whereas 2-MP is converted to 8-hydroxy-2-mercaptopurine as the expected end product in one step. Surprisingly, in contrast to the other thiopurines, enzymatic hydroxylation of 2-MP showed a unique hyperchromic effect at 264 nm as the reaction proceeded. However, when 2-TX is used as the substrate, it is hydroxylated to 2-thiouric acid. The enzymatic hydroxylation of 2-MP is considerably faster than that of 6-MP, while 6-TX and 2-TX show similar rates under identical reaction conditions. The reason why 2-MP is a better substrate than 6-MP and how the chemical nature and position of the functional groups present on the thiopurine substrates influence xanthine oxidase activity are discussed.     

Unique presence of 2-methylthio-ribosylzeatin in the transfer ribonucleic acid of the bacterium Pseudomonas aeruginosa

Analysis of ³⁵S labled nucleosides prepared from tRNA of Pseudomonas aeruginosa by phosphocellulose column chromatography, thin layer chromatography and Sephadex LH-20 column chromatography revealed the presence of 2-methylthioribosylzeatin in it.     

Isolation and crystal structure of 5-hydroxy-2,8-dimethyl-6,7-dimethoxybenzopyran-4-one from Couepia paraensis

A highly substituted chromone constituent of Couepia paraensis was isolated and identified as 5-hydroxy-2,8-dimethyl-6,7-dimethoxychromone by spect     

月腺大戟根中有效成分乙素和丙素的结构研究

本文主要报道从月腺大戟(Euphorbia ebracteolata Hayata)根中分离出的对结核菌有抑制作用的晶Ⅵ(乙素)和晶Ⅶ(丙素)的化学结构。经化学反应及光谱鉴定,确定晶Ⅵ为2,4-二羟基-6-甲氧基-3-甲基-苯乙酮,晶Ⅶ为2-羟基-6-甲氧基-3-甲基-1-苯乙酮-4-6-葡萄糖甙。乙素为首次分离的天然产物,丙素为新的化合物。该植物提取物对结核病有明显疗效。     

Relationships between 4-Hydroxy-2-nonenal, 2-Thiobarbituric Acid Reactive Substances and n-6 Polyunsaturated Fatty Acids in Refrigerated and Frozen Pork

The relationships between 4-hydroxy-2-nonenal (HNE), 2-thiobarbituric acid reactive substances (TBARS) and n-6 polyunsaturated fatty acids (n-6 PUFAs) were investigated for pork stored at 0, -20 and -80°C. A significant linear correlation was apparent between HNE and TBARS for the pork stored at each temperature. However, the n-6 PUFA content remained unchanged during storage.     

A new dihydrobenzofuran from Liatris provincialis

A chloroform extract of Liatris provincialis Godfrey gave as a minor component a new dihydrobenzofuran, whose structure was established as I.     

Identification of specific binding sites for leukotriene C4 in human fetal lung

Specific leukotriene C₄ (LTC₄) binding sites were identified in membrane preparations from human fetal lung. Specific binding of [³H]-LTC₄ represented 95 percent of total binding, reached steadystate within 10 minutes and was rapidly reversible upon addition of excess unlabeled LTC₄. Binding assays were performed at 4°C under conditions which prevented metabolism of [³H]-LTC₄ (80 mM serineborate, 10 mM cysteine, 10 mM glycine). Under these conditions, greater than 95 percent of the membrane bound radioactivity, as analyzed by high performance liquid chromatography, co-eluted with the LTC₄ standard. Computer-assisted analyses of saturation binding data showed a single class of binding sites with a dissociation constant (K_d) of 26 + 6 nM and a density (B_max) of 84 ± 18 pmol/mg protein. Pharmacological specificity was demonstrated by competition studies in which specific binding of [³H]-LTC₄ was displaced by LTC₄ and its structural analogs with inhibition constants (K_j) of 10 to 30 nM, whereas LTD₄, diastereoisomers of LTD₁, LTE₄ and the end organ antagonist FPL 55712 were 150 to 700 fold less potent competitors than LTC₄. These results provide evidence for specific, reversible, saturable, high affinity binding sites for [³H]-LTC₄ in human fetal lung membranes.     

白腐菌SQ01锰过氧化物酶对联苯中间代谢物的转化北大核心CSCD

【目的】在对白腐菌栓菌(Trametes sp.)SQ01锰过氧化物酶(MnP)纯化的基础上,通过MnP对HOPDAs的转化实验,了解白腐菌MnP对2-羟基-6-氧-6-苯基-2,4-己二烯酸(HOPDA)及其衍生物的作用,揭示MnP新的催化特性。【方法】利用紫外可见光谱法分析锰过氧化物酶对10种不同取代基的HOPDAs转化情况,并对锰过氧化物酶的稳态动力学参数进行了测定;红外光谱法分析了HOPDA及其产物的分子结构。【结果】锰过氧化物酶可以转化HOPDA及其卤代HOPDAs,特别是锰过氧化物酶可以催化3,8,11-3Cl HOPDA,而这一物质几乎不能被联苯水解酶(2-羟基-6-氧-6-苯基-2,4-己二烯酸水解酶)和红球菌(Rhodococcus sp.)R04转化。稳态动力学分析表明,在5种HOPDAs中,HOPDA是锰过氧化物酶的最适底物,3,10-2F HOPDA的转化效率(k_(cat)/K_m)是最高的。紫外可见光谱分析表明,锰过氧化物酶在转化HOPDA及其衍生物时最大吸收峰在可见光区均会发生蓝移。红外分析表明,锰过氧化物酶可以使HOPDA的共轭双烯转化为单烯,C_β上的羟基消失。【结论】锰过氧化物酶能够有效降解HOPDA及其衍生物,这为联苯及其中间代谢物的顺利降解提供了新的策略。     

Imidazole open ring 7-methylguanine: an inhibitor of DNA synthesis

Guanine methylated at the N7 position (me7G) is susceptible to cleavage of the imidazole ring yielding: 2,6-diamino-4-hydroxy-5N-methyl-formamidopyrimidine (rom7G). DNA synthesis catalysed by E.coli DNA polymerase I, using as templates poly(dGC) containing either me7G or rom7G, show that rom7G blocks DNA chain elongation. It implies a potential killing effect. Furthermore rom7G does not induce mispairing with either dAMP or dTMP. me7G does not affect DNA synthesis. The results suggest that, beside AP-sites, rom7G is a potential killing lesion in cells treated by alkylating agents.     

Aliphatic hydroxy-ketones from Curculigo orchioides rhizomes

Two new aliphatic hydroxy-ketones, isolated from the rhizomes of Curculigo orchioides, have been characterized as 27-hydroxytriacontan-6-one and 23-hydroxytriacontan-2-one, respectively, by spectral data and chemical studies.     

Constitutions of diarylpropanoids from Virola multinervia

The wood of Virola multinervia Ducke (Myristicaceae) contains sitosterol, stigmasterol and two novel diarylpropanoids virolane [1-(2-hydroxy-4-methoxyphenyl)-3-(3,4-methylenedioxyphenyl)-propane] and virolanol [2-hydroxy-1-(2-hydroxy-4-methoxyphenyl)-3-(3,4-methylenedioxyphenyl)-propane].     

Inhibitors of HIV protease: Unique non-peptide active site templates

New templates were designed and prepared which straddle the active site of HIV-1 protease. These templates were designed to be ‘flexible scaffolds’ upon which substituents could be appended to fill the pockets of HIV protease. The new templates prepared and analysed were 4-hydroxy-5H-furan-2-ones, 4-hydroxy-5,6-dihydropyrones, 3-hydroxy-cyclohex-2-enones, and 4-hydroxy-2(1H)-pyridinones, of which the 4-hydroxy- 5,6-dihydropyrones were found to be the most potent inhibitors of HIV-1 protease.     

Antifungal Constituent of Sapium japonicum

An antifungal constituent, C₉H₁₄O₃, containing allenic double bond, was isolated from the leaves of Sapium japonicum (Euphorbiaceae). The structure of this antifungal constituent was shown to be methyl 8-hydroxy-5, 6-octadienoate.     

Adenosine binding sites in brain; relationship to endogenous levels of adenosine and to its physiological and regulatory roles

Adenosine is an endogenous component of brain tissue and is present at micromolar concentrations, well above those required to saturate the adenylate cyclase-linked receptors recently demonstrated by binding studies. It is suggested that a major binding site for adenosine may be the enzyme S-adenosyl homocysteinase, and modulation of the equilibrium catalysed by this reaction may regulate the concentration of adenosine available for stimulation of cyclic AMP production and its other physiological roles.     

Methodological considerations and factors affecting 8-hydroxy-2′-deoxyguanosine analysis

Oxidative stress is related to a number of diseases due to the formation of reactive oxygen species (ROS). There are also several substances found in the occupational environment or as life style related situations that generates ROS. A stable biomarker for oxidative stress on DNA is 8-hydroxy-2′-deoxyguanosine (8-OH-dG).

A potential problem in the work-up and analysis of 8-OH-dG is oxidation of dG with false high levels as a result of analysis. This paper summarizes and discusses some of the critical moments in terms of auto-oxidation. The removal of transition metals, low temperatures, absence of isotopes (or 2′-deoxyguanosine) and incubation times are all important factors. Removal of oxygen is complicated while the problem is reduced if a nitroxide (TEMPO) is added during work-up. Certain reducing agents and enzymes could be critical if added during work-up.

The application of the ³²P-HPLC method to analyze 8-OH-dG is discussed. The ³²P-HPLC method is suitable for 8-OH-dG analysis and avoids several factors that oxidizes dG by removal of dG before addition of isotopes. Factors of crucial importance (columns, eluents, gradients and detection of ³²P) for the analysis of 8-OH-dG are commented upon and certain recommendations are made to make it possible to apply the ³²P-HPLC methodology for this type of analysis.