491-67-8Relevant articles and documents
Enzyme-polysaccharide interaction and its influence on enzyme activity and stability
Li, Jian,Jiang, Zhongyi,Wu, Hong,Liang, Yanpeng,Zhang, Yufei,Liu, Jiaxian
, p. 160 - 166 (2010)
An attempt was made to probe and elucidate the influence of three kinds of polysaccharides including the negatively charged sodium carboxymethyl cellulose (CMC), the uncharged methyl cellulose (MC) and the positively charged sodium carboxymethyl chitosan (CMCS), on the catalytic activity and stability of the model enzyme, β-d-glucuronidase (GUS). DSC analysis showed that the denaturing temperature of GUS was increased by 7 °C in the presence of CMC, but decreased in the presence of MC or CMCS by 5 and 3 °C, respectively. This variation was in good accordance with changes in the enzyme's catalytic activity. Circular dichroism was employed to characterize the conformational changes of GUS before and after the addition of the polysaccharide. It suggested that charged polysaccharides, CMC and CMCS, were favorable for improving the pH stability and the storage stability of GUS, whereas uncharged MC did not show such a stabilizing effect. At an elevated temperature up to 70 °C, GUS in CMC solution remained 78% activity and displayed the highest thermal stability among the three enzyme-polysaccharide pairs. The electrostatic interaction between enzyme and polysaccharides was closely relevant to the enzyme conformation, activity and stability.
ADDITIONAL FLAVONOIDS FROM ELICITOR-TREATED CELL CULTURES OF CEPHALOCEREUS SENILIS
Liu, Qin,Dixon, Richard A.,Mabry, Tom J.
, p. 167 - 170 (1993)
Five major flavonoids induced by chitin in Cephalocereus senilis cell suspension cultures have been reported previously.We describe here five minor induced flavonoids including two new and three known ones.The two new compounds are (2S)-5,6,7-trihydroxyflavanone 7-glycoside and baicalein 7-(6''-malonylglucoside).
Biotransformation of Chrysin to Baicalein: Selective C6-Hydroxylation of 5,7-Dihydroxyflavone Using Whole Yeast Cells Stably Expressing Human CYP1A1 Enzyme
Williams, Ibidapo S.,Chib, Shifali,Nuthakki, Vijay K.,Gatchie, Linda,Joshi, Prashant,Narkhede, Niteen A.,Vishwakarma, Ram A.,Bharate, Sandip B.,Saran, Saurabh,Chaudhuri, Bhabatosh
, p. 7440 - 7446 (2017)
Naturally occurring polyphenolic compounds are of medicinal importance because of their unique antioxidant, anticancer, and chemopreventive properties. Baicalein, a naturally occurring polyhydroxy flavonoid possessing a diverse range of pharmacological activities, has been used in traditional medicines for treatment of various ailments. Apart from its isolation from natural sources, its synthesis has been reported via multistep chemical approaches. Here, we report a preparative-scale biotransformation, using whole yeast cells stably expressing human cytochrome P450 1A1 (CYP1A1) enzyme that allows regioselective C6-hydroxylation of 5,7-dihydroxyflavone (chrysin) to form 5,6,7-trihydroxyflavone (baicalein). Molecular modeling reveals why chrysin undergoes such specific hydroxylation mediated by CYP1A1. More than 92% reaction completion was obtained using a shake-flask based process that mimics fed-batch fermentation. Such highly efficient selective hydroxylation, using recombinant yeast cells, has not been reported earlier. Similar CYP-expressing yeast cell based systems are likely to have wider applications in the syntheses of medicinally important polyphenolic compounds.
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Litvinenko,Denikeeva
, (1971)
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Oxidation of Flavone, 5-Hydroxyflavone, and 5,7-Dihydroxyflavone to Mono-, Di-, and Tri-Hydroxyflavones by Human Cytochrome P450 Enzymes
Nagayoshi, Haruna,Murayama, Norie,Kakimoto, Kensaku,Tsujino, Masaki,Takenaka, Shigeo,Katahira, Jun,Lim, Young-Ran,Kim, Donghak,Yamazaki, Hiroshi,Komori, Masayuki,Guengerich, F. Peter,Shimada, Tsutomu
, p. 1268 - 1280 (2019/05/07)
Biologically active plant flavonoids, including 5,7-dihydroxyflavone (57diOHF, chrysin), 4′,5,7-trihydroxyflavone (4′57triOHF, apigenin), and 5,6,7-trihydroxyflavone (567triOHF, baicalein), have important pharmacological and toxicological significance, e.g., antiallergic, anti-inflammatory, antioxidative, antimicrobial, and antitumorgenic properties. In order to better understand the metabolism of these flavonoids in humans, we examined the oxidation of flavone, 5-hydroxyflavone (5OHF), and 57diOHF to various products by human cytochrome P450 (P450 or CYP) and liver microsomal enzymes. Individual human P450s and liver microsomes oxidized flavone to 6-hydroxyflavone, small amounts of 5OHF, and 11 other monohydroxylated products at different rates and also produced several dihydroxylated products (including 57diOHF and 7,8-dihydroxyflavone) from flavone. We also found that 5OHF was oxidized by several P450 enzymes and human liver microsomes to 57diOHF and further to 567triOHF, but the turnover rates in these reactions were low. Interestingly, both CYP1B1.1 and 1B1.3 converted 57diOHF to 567triOHF at turnover rates (on the basis of P450 contents) of >3.0 min-1, and CYP1A1 and 1A2 produced 567triOHF at rates of 0.51 and 0.72 min-1, respectively. CYP2A13 and 2A6 catalyzed the oxidation of 57diOHF to 4′57triOHF at rates of 0.7 and 0.1 min-1, respectively. Our present results show that different P450s have individual roles in oxidizing these phytochemical flavonoids and that these reactions may cause changes in their biological and toxicological properties in mammals.
Synthesis of oroxylin A starting from naturally abundant baicalin
Fujita, Rie,Hanaya, Kengo,Higashibayashi, Shuhei,Sugai, Takeshi
, p. 1165 - 1174 (2019/07/31)
– A new approach to oroxylin A, a monomethylated trihydroxyflavone, is described. The starting material was baicalin, a representative naturally abundant flavonoid glucuronide. First, conditions for the cleavage of the glycosidic bond were established, using a mixture of water and conc. sulfuric acid (5:2) at 121 °C for 40 min. The hydrolysis was performed in a high-pressure steam sterilizer so that the temperature and reaction time were precisely controlled. Subsequent acetylation of the crude material furnished baicalein 6,7-diacetate on a preparative scale and in a reproducible manner. Next, the C-7 position was protected site-selectively with a methoxymethyl (MOM) group, taking advantage of an unexpected sequential migration of the two acetyl groups among the C-5, C-6, and C-7 positions under basic conditions. The removal of the two remaining acetyl groups followed by site-selective methylation of the C-6 position furnished 5-hydroxy-6-methoxy-7-methoxymethoxyflavone (oroxylin A C-7 MOM ether). Finally, by the deprotection of the MOM ether, oroxylin A was obtained in 6 total steps and 62% overall yield from baicalin.