Potent antimutagenic activity of white tea in comparison with green tea inthe Salmonella assay

There is growing interest in the potential health benefits of tea, includin g the antimutagenic properties. Four varieties of white tea, which represen t the least processed form of tea, were shown to have marked antimutagenic activity in the Salmonella assay, particularly in the presence of S9. The m ost active of these teas, Exotica China white tea, was significantly more e ffective than Premium green tea (Dragonwell special grade) against 2-amino- 3-methylimidazo[4,5-f]quinoline (IQ) and four other heterocyclic amine muta gens, namely 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 2-amino -3,4,8-trimethyl-3H-imidazo[4,5-f]quinoxaline (4,8-DiMeIQx), 2-amino-1-meth yl-6-phenylimidazo[4,5-b]pyridine (PhIP), and 3-amino-1-methyl-5H-pyrido[4, 3-b]indole (Trp-P-2). Mechanism studies were performed using rat liver S9 i n assays for methoxyresorufln O-demethylase (MROD), a marker for the enzyme cytochrome P4501A2 that activates heterocyclic an-tines, as well as Salmon ella assays with the direct-acting mutagen 2-hydroxyamino-3-methylimidazo[4 ,5-f]quinoline (N-hydroxy-IQ). White tea at low concentrations in the assay inhibited MROD activity, and attenuated the mutagenic activity of N-hydrox y-IQ in the absence of S9. Nine of the major constituents found in green te a also were detected in white tea, including high levels of epigallocatechi n-3-gallate (EGCG) and several other polyphenols. When these major constitu ents were mixed to produce 'artificial' teas, according to their relative l evels in white and green teas, the complete tea exhibited higher antimutage nic potency compared with the corresponding artificial tea. The results sug gest that the greater inhibitory potency of white versus green tea in the S almonella assay might be related to the relative levels of the nine major c onstituents, perhaps acting synergistically with other (minor) constituents , to inhibit mutagen activation as well as 'scavenging' the reactive interm ediate(s). (C) 2001 Elsevier Science B.V. All rights reserved.