The Inhibitory Effect of Chinese Tea and Its Polyphenols on in vitro and in vivo N-Nitrosation

The objective of this study is to evaluate the possible role of Chinese tea as a naturalinhibitor of N-nitrosation,and to compare the relative inhibitory potency of various kinds ofChinese tea in vitro and in vivo.Studies on the inhibitory effect of 145 samples of Chinese teaon the formation of N-nitrosomorpholine(NMOR)showed that the inhibitory potency of the7 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 ChineseGongfu 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 alsoconfirmed in 3 human volunteer experiments.Drinking tea after meal had a greater effect thandrinking it before meal.It is concluded that Chinese tea can exert a relatively strong inhibitorypotency for N-Nitroso compounds(NOC)fo