Catechins methylation

Cren-Olive C, Tessier E, Duriez P, Rolando C. Structure-activity relationship for the inhibition of LDL oxidation by catechin methylated metahoAtes and analogues. Free Rad Biol Med. In press. 

Sweeny JG, lacobucci GA. Regiospecificity of (+)-catechin methylation. J Org Chem 1979 44 2298-2299. 

Tea flavonoids, or tea extracts, are increasingly being added to foods. However, interactions with food and drink components remain unclear, and thus need to be carefully assessed in order that the full potential benefits from consuming tea, in whatever form, can be achieved. Meanwhile, tea catechins themselves undergo extensive O-methylation, glucuronidation, sulphation and ring fission... 

PEDRiELLi p and SKIBSTED L H (2002) Antioxidant syneigy and regeneration effect of quercetin, (-)epicatechin, and (+)-catechin on a-tocopherol in homogeneous solutions of peroxidating methyl linoleate, JAgric Food Chem, 50, 7138-44. 

Model systems indicate that aldehydes may also be produced by the action of polyphenoloxidases on amino acids in the presence of catechin, all of which are present in coffee beans at some stage between green and roasted. For example, valine yields isobutanal, leucine yields isopentanal, and isoleucine yields 2-methyl-butanal.14 Some of these aldehydes probably undergo condensation reactions in the acidic medium of the roasted bean when moisture is present.15 Some dienals in green coffee beans have recently been identified as (E,E)-2,4- and (E,Z)-2,4-nonadienal and (E,E)-2,4- and (E,Z)-2,4-decadienal.18... 

Catechin, epi-gallo LP" Catechin-3-0-(3 -0-methyl) -gallate, epi(-) Lf 0.08% Catechin-3-0-(3-0-methyl)-gallate,... 

The HPLC-FTIR technique has recently been used to identify six catechins and two methyl-xanthines present in green tea extracts." " A reversed-phase separation of the compounds was performed on a C-18 column equilibrated at 30°C using an isocratic mobile phase of acetonitrile-0.1% formic acid (15 85), prior to introduction to the deposition interface linked to the FTIR detector. The solvent was evaporated at 130°C and spectra were collected every 6 sec during the run. Two distinct designs for HPLC-FTIR interfaces have been developed flow cells and solvent elimination systems. Flow cell systems acquired spectra of the eluent in the solvent matrix through IR transparent, nonhydroscopic windows. The... 

Suzuki, M., Sano, M., Yoshida, R., Degawa, M., Miyase, T., and Maeda-Yamamoto, M., Epimerization of tea catechins and 0-methylated derivatives of (—)-epigallocatechin-3-0-gallate relationship between epimerization and chemical structure, J. Agric. Food Chem., 51, 510, 2003. 

Lu, H., Meng, X., and Yang, C.S., Enzymology of methylation of tea catechins and inhibition of catechol-0-methyltransferase by (—)-epigallocatechin gallate. Drug Metab. Dispos., 31, 572, 2003. 

The synthetic protocol (Scheme 11.2) toward the flavan-3-ol permethylaryl ethers is based upon the transformation of rc7ro-chalcones into 1,3-diarylpropenes. These compounds are then subjected to asymmetric dihydroxylation to give diarylpropan-l,2-diols that are used as chirons for essentially enantiopure flavan-3-ols. The protocol is demonstrated in Scheme 11.2 for the synthesis of the tetra-(9-methyl-3-(9-acetyl derivatives 61a, 61b, 62a, and 62b of (-l-)-catechin (2), (—)-e 7-catechin, (—)-epicatechin (3), and (+)-e 7-epicatechin (4). ... 

Simultaneous deprotection and cyclization of diols 60a and 60b with 3 M HCl in MeOH followed by acetylation yielded the 2,3-trans- ( 50%) (61a and 61b) and for the first time 2,3-cw-flavan-3-ol methylether acetate derivatives ( 20%) (62a and 62b) in excellent enantiomeric excesses (>99%). The optical purity was assessed by H NMR using [Eu(hfc)3] as chiral shift reagent. The absolute configuration of the derivatives of the tram- and cii-flavan-3-ol derivatives was assigned by comparison of CD data with those of authentic samples in the catechin or epicatechin series flavan-3-ols. Thus, the absolute configuration of the flavan-3-ol methyl ether acetates confirms the assigned configuration of the diols as derived from the Sharpless model. 

Elaeagnus pungens Thunb. E. umbellata Thunb. Hu Tin Chi (root, leaf, fruit) Harman, tetrahydroharman, dihydroharman, 2-methyl-l,2,3, 4-tetrahydro-P-carboline, caffeic acid, chlorogenic acid, catechin, neochlorogenic acid, epicatechin.48 Treat coughs, watery diarrhea, an astringent in hemoptysis. 

Other authors suggested that catechins are converted to glucuronyl derivatives in the intestinal mucosa and are further metabolized by methylation, sulfation and conjugation with glucuronic acid, sulfate and glycine [101]. 

LC/ESI-MS analyses were applied to determine urinary glucuronidated and sulfated tea catechins after the administration of green tea to humans, mouse and rats [109]. The major conjugates were identified as monoglucuronides and monosulfates of EGC and EC. Besides these metabolites, also G-methyl-EGC-G-glucuronides, O-sulfates and O-methyl-EC-O-sulfates in human urine were detected. Furthermore, the ring-fission metabolites of EGC and (-)-epicatechin, 5-(3 ,4 ,5 -trihydroxyphenyl)-y-valerolactone and 5-(3 ,4 -dihydroxyphenyl)- valerolactone respectively, have been detected in the monoglucuronide and monosulfate forms. 

Ring contraction was also noted on acetolysis of 3-tosyltetra-O- methyl-(+)-catechin the 2,3-dihydrobenzo[Z> ]furan formed can be oxidized to the benzo[f>]furan (Scheme 105) (66JCS(C)634). The 2-phenylbenzo[6]furan and its 2,3-dihydro derivative are degradation products of lignin and as such have been investigated extensively. 

The structure of 8-bromotetra-0-methyl-(+)-catechin (161) has been determined. The conformation of the heterocyclic ring in the crystal is between a C-2, C-3 half-chair and a C-2 sofa arrangement. The 2R,1R absolute configuration of (-l-)-catechin is confirmed (78CC695). 

Meng X, Sang S, Zhu N, Lu H, Sheng S, Lee MJ, Ho CT, Yang CS. 2002. Identification and characterization of methylated and ring-fission metabolites of tea catechins formed in humans, mice, and rats. Chem Res Toxicol 15 1042-1050. 

The major metabolic pathways for tea catechins include glucuronidation, sulfation, and methylation. There are species and tissue-specific differences in... 

Nagai, M., Conney, A.H., and Zhu, B.T., Strong inhibitory effects of common tea catechins and bioflavonoids on the O-methylation of catechol estrogens catalyzed by human Ever cytosolic catechol-O-methyltransferase, Drug Metab. Dispos., 32,497, 2004. 

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