An investigation on the antimutagenic properties of South African herbal teas

The antimutagenic properties of South African herbal teas were investigated using the Salmonella typhimurium mutagenicity assay. Aqueous extracts of f ermented and unfermented rooibos tea (Aspalathus linearis) and honeybush te a (Cyclopia intermedia) both possess antimutagenic activity against 2-acety laminofluorene (2-AAF) and aflatoxin B-1 (AFB(1))-induced mutagenesis using tester strains TA98 and TA100 in the presence of metabolic activation. A f ar less inhibitory effect was noticed against the direct acting mutagens, m ethyl methanesulfonate (MMS), cumolhydroperoxide (CHP), and hydrogen peroxi de (H2O2) using TA102, a strain designed to detect oxidative mutagens and c arcinogens. Depending on the mutagen used, the unfermented tea exhibited th e highest protective effect. A similar response regarding the protection ag ainst mutagenesis was obtained when utilising different variations of the d ouble layer Salmonella assay. The double layer technique proved to be more effective to detect the protective effect of the different tea preparations against the direct acting mutagens. With respect to indirect mutagens, the highest protection was noticed when the carcinogen was metabolically activ ated in the presence of the tea extract as compared with when the tea extra ct was incubated in a separate layer with the bacteria. The current data su ggest that two mechanisms seem to be involved in the antimutagenicity of th e tea extracts towards carcinogens that require metabolic activation: (i) t he tea components may interfere with cytochrome P350-mediated metabolism of these mutagens and (ii) the direct interaction between the tea constituent s, presumably the polyphenolic compounds, with the promutagens and/or the a ctive mutagenic metabolites. However, the mild and/or lack of protection an d in some cases even enhancement of mutagenesis induced by direct acting or oxidative mutagens, provide new perspectives regarding the role of the pol yphenolic compounds known to exhibit antioxidant properties, in the protect ion against mutagenesis in the Salmonella assay. The present study provides the first evidence on the antimutagenic activity of honeybush tea and furt her evidence on the antimutagenicity of rooibos tea. (C) 2000 Elsevier Scie nce B.V. All rights reserved.