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.