Investigating the safety of plants used in South African traditional medicine: testing for genotoxicity in the micronucleus and alkaline comet assays.

Previous studies indicate that traditional botanical remedies can be valuable for treating human disease. The potential risk from long-term use of such remedies has not, however, been fully investigated, especially in terms of their potential carcinogenic activity. In the present study, 51 South African plant species were selected on the basis of their use in traditional medicine and crude extracts were sequentially prepared from different dried plant parts using dichloromethane followed by 90% methanol. These extracts were tested for genotoxic activity in human peripheral blood lymphocytes using the micronucleus test, with further testing of select extracts using the alkaline comet assay. Screening results indicated the induction of significant numbers of micronuclei by many of the plant extracts. Several samples also induced DNA damage in human white blood cells using the alkaline comet assay. Although a number of these plants are recognised as toxic by traditional healers, several plants that are used in common remedies were found to be genotoxic and potentially dangerous. Environ. Copyright 2003 Wiley-Liss, Inc.