Evaluation or genotoxicity of medicinal plant extracts by the comet and VITOTOX® tests

We report the results of our genotoxic evaluation of extracts from three medicinal plants-Acacia nilotica, Juglans regia, and Terminalia cbebula-and the herbal drug Triphala employing the VITOTOX (R) and comet tests. These tests detect DNA damage in prokaryotic and eukaryotic test systems, respectively. In the VITOTOX (R) test, none of the extracts were identified as genotoxic. In the comet assay, extracts of Acacia nilotica showed statistically significant DNA damage only in a concentration of 2500 ppm (highest tested dose), whereas extracts from Juglans regia showed significant damage in concentrations above 250 ppm and more. Extracts from Terminalia chebula and Tripahala significantly increased DNA damage in a concentration above 500 ppm. This is not considered contradictory, because DNA damage in the alkaline comet assay may not be permanent and hence may not necessarily result in mutations. All the extracts were previously found in the Ames assay to have potent antimutagenic effects against the direct acting mutagens NPD, sodium azide, and the S9-dependent mutagen 2-AF. The results of the previous study using the Ames assay are in conformity with those of the VITOTOX (R) test. It was found that the extracts were safe in concentrations of up to 1000 mu g/0.1 mL and 25 00 mu g/0.1 mL. A literature survey also showed that plant extracts can be mutagenic as well as antimutagenic depending on the test system used. This indicates that a battery of assays is needed before any conclusion can be reached.