title: Inhibitory effect(s) of polymeric black tea polyphenol fractions on the formation of [(3)H]-B(a)P-derived DNA adducts.
abstract: Five polymeric black tea polyphenol fractions (PBP-1-5) were isolated from a popular brand of black tea. The effect of these PBPs and epigallocatechin gallate (EGCG), a major green tea polyphenol, was studied on the formation of [(3)H]-B(a)P-derived DNA adducts in vitro, employing rat liver microsomes. PBP-1-3 inhibited microsome-catalyzed [(3)H]-B(a)P-derived DNA adduct formation in vitro in a dose-dependent manner. This inhibition was further enhanced on preincubation of microsomes with each of the PBPs. PBP-4 was not effective per se and required preincubation with microsomes to exhibit its inhibitory effect, whereas PBP-5 remained ineffective with or without preincubation with microsomes. Further investigations revealed that the observed decrease in [(3)H]-B(a)P-DNA adduct formation was due to inhibition of isozymes of CYP450s by PBPs. Overall, results suggest that polymeric black tea polyphenol fractions retain one of the chemopreventive effects exhibited by the monomeric green tea polyphenol EGCG in vitro.
authors.affiliation: Tobacco Carcinogenesis Group, Cancer Research Institute, Advanced Centre for Treatment, Research and Education in Cancer (ACTREC), Tata Memorial Centre, Kharghar, Navi Mumbai 410 208, India.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Krishnan
authors.forename: Girish B
authors.initials: GB
authors.lastname: Maru
mesh_terms: D000818:Animals; D001564:Benzo(a)pyrene / Q000737:chemistry*; D028241:Camellia sinensis / Q000737:chemistry*; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D018736:DNA Adducts / Q000187:drug effects*; D005419:Flavonoids / Q000494:pharmacology*; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology; D010078:Oxazines / Q000378:metabolism; D010636:Phenols / Q000494:pharmacology*; D018515:Plant Leaves / Q000737:chemistry*; D059808:Polyphenols; D051381:Rats; D017207:Rats, Sprague-Dawley; D014316:Tritium
chemical_list: D018736:DNA Adducts; D005419:Flavonoids; D010078:Oxazines; D010636:Phenols; D059808:Polyphenols; D014316:Tritium; D001564:Benzo(a)pyrene; C007649:ethoxyresorufin; C014180:resorufin; D002392:Catechin; D003577:Cytochrome P-450 Enzyme System; C045651:epigallocatechin gallate