title: The inhibitory effect of Chinese tea and its polyphenols on in vitro and in vivo N-nitrosation.
abstract: The objective of this study is to evaluate the possible role of Chinese tea as a natural inhibitor of N-nitrosation, and to compare the relative inhibitory potency of various kinds of Chinese tea in vitro and in vivo. Studies on the inhibitory effect of 145 samples of Chinese tea on the formation of N-nitrosomorpholine (NMOR) showed that the inhibitory potency of the 7 types of Chinese tea differed greatly, the average blocking rate of green tea (89.04%, n = 60), crush, tear, and curl (CTC) black tea (86.99%, n = 13), brick tea (85.40%, n = 7), jasmine tea (84.99%, n = 21), Oolong tea (82.37%, n = 9), sun-dried tea (61.99%, n = 13) and Chinese Gongfu black tea (54.98%, n = 22), were positively correlated with their polyphenols contents. The inhibitory effect of green tea and black tea on endogenous N-nitrosation was also confirmed in 3 human volunteer experiments. Drinking tea after meal had a greater effect than drinking it before meal. It is concluded that Chinese tea can exert a relatively strong inhibitory potency for N-Nitroso compounds (NOC) formation both in vitro and in humans, and the active constituents may be related to their polyphenols contents, especially the tea catechin derivatives. The results also demonstrated that the amounts of NMOR formed in vitro depended on the molecular structure of tea catechin derivatives and their molar ratios to nitrite.
authors.affiliation: Institute of Nutrition and Food Hygiene, Chinese Academy of Preventive Medicine, Beijing.
authors.forename: Y N
authors.initials: YN
authors.lastname: Wu
authors.forename: H Z
authors.initials: HZ
authors.lastname: Wang
authors.forename: J S
authors.initials: JS
authors.lastname: Li
authors.forename: C
authors.initials: C
authors.lastname: Han
mesh_terms: D000328:Adult; D001704:Biopolymers; D002273:Carcinogens / Q000138:chemical synthesis; D005260:Female; D006801:Humans; D008297:Male; D015394:Molecular Structure; D009602:Nitrosamines / Q000138:chemical synthesis; D015538:Nitrosation; D010636:Phenols / Q000494:pharmacology*; D013048:Specimen Handling; D013662:Tea / Q000737:chemistry
chemical_list: D001704:Biopolymers; D002273:Carcinogens; D009602:Nitrosamines; D010636:Phenols; D013662:Tea; C002741:N-nitrosomorpholine