共查询到20条相似文献,搜索用时 6 毫秒
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Xanthoxylone, a new pentacyclic triterpenoid ketone has been isolated from a rutaccous plant, Xanthoxylum rhetsa. From spectral properties and conversion experiments the structure and stereochemistry of the terpenoid have been deduced as 1. 相似文献
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The constitution of mollugogenol-F, a new triterpenoid sapogenin isolated from Mollugo hirta (family: Ficoidaceae), has been established as 3β,16β,22-trihydroxyisohopane. 相似文献
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By incubation of germinating soybeans with mevalonate-[2-14C] (MVA), radioactivity was incorporated into four sapogenols which were identified by TLC. Unequivocal evidence for the identity of three of the four sapogenols was provided by co-crystallization to constant specific radioactivity. The partition of incorporated radioactivity into lipid- and water-soluble fractions and the pattern of radioactivity of individual sapogenols varied with the mode of administering labeled substrates to soybean seedlings, such as incubation of germinating soybeans with MVA-[2-14C], immersion of roots into MVA-[2-14C] or foliar application of squalene-[14C]. When alfalfa seedlings were incubated with MVA-[2-14C], about two-thirds of the radioactivity incorporated into the sapogenols was associated with medicagenic acid. 相似文献
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Harkishan Singh Vijay K. Kapoor Franco Piozzi Salvatore Passannanti Mariapia Paternostro 《Phytochemistry》1978,17(1):154-155
Isomotiol (fern-8-en-3β-ol) was isolated from the leaves of Strychnos potatorum; it was not known previously as a natural product, but it has been obtained by acidic isomerization of compounds with a fern-7-ene or a fern-9(11)-ene skeleton. From the leaves and the bark mixtures of sitosterol, stigmasterol and campesterol were also isolated. 相似文献
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Mallotin, a new C32 triterpene from Mallotous stenanthus, has been isolated and its structure established as 24,24-dimethyl-lanosta-7,25-dien-3α-ol. 相似文献
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Tsutomu Nakanishi Hiroko Terai Masao Nasu Iwao Miura Kaisuke Yoneda 《Phytochemistry》1982,21(6):1373-1377
Two new triterpene glycosides, a diglycoside (as the corresponding methyl ester) and a bis-desmoside were isolated from leaves of Ilex cornuta. The 相似文献
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利用各种色谱技术从马缨杜鹃(Rhododendron delavayi Franch.)茎中分离得到10个化合物。通过波谱学方法鉴定为异鼠李素(1),nectandrin B(2),resveratrol-3-O-β-D-glucoside(3),lysidiside N(4),19α-hydroxyasiatic acid(5),白桦脂酸(6),3β-hydroxylup-12-en-28-oic-acid(7),obtusalin(8),methyl 2,4-dihydroxy-6-methylbenzoate(9),2,5-dihydroxy-3-methoxytoluene(10)。化合物2~9为首次从该种植物中分离得到。 相似文献
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Using differently labelled precursors, it was established that rhododendrin (3-(4-hydroxyphenyl)-1-methylpropyl-β-D-glucopyranoside) is formed through the phenylpropane pathway via p-coumaryl alcohol, dihydro-p-coumaryl alcohol and C-methylation of the γ-C-atom of the C6C3 unit with methionine supplying the methyl group. It was demonstrated that the pro-(S)-hydrogen atom of dihydro-p-coumaryl alcohol is replaced stereospecifically by the methyl group. 相似文献
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A new triterpene, betulafolienpentaol, 3α,12β,17,20,25-pentahydroxy dammar-23-trans-ene and two other known triterpenes were isolated from Betula platyphylla. The latter compounds were identified as betulafolientetraol and betulafolientetraol-A, respectively. 相似文献
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The structure of lantanilic acid, a new triterpene isolated from the leaves of Lantana camara, has been determined as the β,β-dimethylacryloyl ester of lantaninilic acid. 相似文献
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木栓酮及其衍生物在植物中普遍存在且种类繁多,具有丰富的生理药理学活性。木栓酮衍生物是以木栓酮为骨架经细胞色素氧化酶P450(cytochromeP450,CYP450)及UDP葡萄糖醛酸转移酶(UDP-glucuronosyltransferase, UGT)修饰而来。植物中天然木栓酮及其衍生物的含量极低,传统的萃取分离和化学合成效率低、能耗高且污染环境,因此,利用酿酒酵母作为宿主菌生产木栓酮及其衍生物是一种高效且环保的策略。本文从增加前体含量、提高酶活性和产物合成的亚细胞定位等方面介绍并展望了木栓酮在酿酒酵母中高效生产的策略,并介绍了目前几种常见的木栓酮衍生物研究现状,从根据碳骨架相似性挖掘CYP450、蛋白质工程改造CYP450和合成代谢基因簇的挖掘等方面展望了木栓酮衍生物的合成途径解析的新思路。 相似文献
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Jacoumaric acid isolated from Jacaranda caucana is shown to be 2α-hydroxy-3β-trans-p-coumaryloxy-urs-12-en-28-oic acid. 相似文献
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Stereochemistry of binding of thiophosphate analogs of ATP and ADP to carbamate kinase, glutamine synthetase, and carbamoyl-phosphate synthetase 总被引:1,自引:0,他引:1
Thiophosphate analogs of adenine nucleotides were used to establish the absolute stereochemistry of nucleotide substrates in the reactions of carbamate kinase (Streptococcus faecalis), unadenylylated glutamine synthetase (Escherichia coli), and carbamoyl-phosphate synthetase (E. coli). 31P NMR was used to determine that carbamate kinase uses the B isomer of Ado-5′-(2-thioPPP) in the presence of Mg2+. The stereospecificity of the reaction with carbamate kinase was not reversed by Cd2+ suggesting that the metal ion does not bind to the β-phosphoryl group or that both Mg2+ and Cd2+ bind to the sulfur atom. Carbamate kinase uses both A and B isomers of Ado-5′-(1-thioPP) with Mg2+ and Cd2+. We have previously reported that carbamoyl-phosphate synthetase uses the A isomer of Ado-5′-(2-thioPPP) at both ATP sites with Mg2+ (Raushel et al., 1978J. Biol. Chem.253, 6627). Current experiments show that the stereospecificity is reversed by Cd2? and that both A and B isomers are used when Zn2+ is present. With Ado-5′-(1-thioPPP), the B isomer is used with Mg2+, the A isomer with Cd2+, and both isomers with Zn2+. Neither carbamate kinase nor carbamoyl-phosphate synthetase utilized Co(III)(NH3)4ATP as a substrate and thus we can only speculate that the Δ chelate ring configuration is the chelate structure utilized by carbamoyl-phosphate synthetase (based on the analogy between thiophosphate-ATP analogs and Co3+-ATP analogs utilized by hexokinase (E. K. Jaffe, and M. Cohn, 1978Biochemistry17, 652). If the sulfur of the β-phosphoryl of Ado-5′-(2-thioPPP) binds to the metal ion with carbamate kinase, then the Δ chelate ring is also used in this enzyme that catalyzes one of the steps in the overall reaction catalyzed by carbamoyl-phosphate synthetase. Glutamine synthetase reacts with the B isomer of both Ado-5′-(2-thioPPP) and Ado-5′-(1-thioPPP) in the presence of Mg2+. When Co2+ is used with this enzyme the A and B isomers of both thio-ATP compounds are substrates. Co(III)(NH3)4ATP is not a substrate for glutamine synthetase. Glutamine synthetase is therefore different from the two previously mentioned enzymes in that it used the opposite A ring configuration for the metal-ATP chelate. 相似文献