Mutagenic screening of some commonly used medicinal plants in Nigeria

The uses of medicinal plants have always been part of human culture. The World Health Organization estimates that up to 80% of the world's population relies on traditional medicinal system for some aspect of primary health care. However, there are few reports on the toxicological properties of most medicinal plants especially, their mutagenicity and carcinogenicity. Therefore, this research is to determine the mutagenic potentials of Morinda lucida [Oruwo (Root)], Azadirachta indica [Dongoyaro (Leaf)], Terapluera tetraptera [Aridan (Fruit)], Plumbago zeylanica [Inabiri (Root)], Xylopia aethiopica [Erunje (Fruit)], Newbouldia laevis [Akoko (Leaf)], Alstonia boonei [Ahun (Bark)], Enantia chlorantha [Awopa (Bark)], and Rauvolfia vomitoria [Asofeyeje (Root)] using the Allium cepa Linn. model and the modified Ames assay. Allium cepa model was used to determine the mean root length, mitotic index and chromosomal aberrations effects of these plants on onion bulbs using 0.1, 1, 5 and 10mg/ml concentration of the plant extracts. The modified Ames test which is a modification of the standard Ames test as described by Ames et al. [Ames, B.N., McCann, J., Yamasaki, E., 1975. Methods for detecting carcinogens and mutagens with the Salmonella/mammalian microsome mutagenicity test. Mutation Research 31, 347-364] was done using Escherichia coli (0157:H7) that has the phenotypic characteristics of glucose and lactose fermentation, motile, urease negative, indole positive and citrate negative. The results obtained from Allium cepa assay showed increasing root growth inhibition with increased concentration, decreasing mitotic index with increased concentration and chromosomal aberrations. The modified Ames test showed an alteration in the biochemical characteristics of Escherichia coli (0157:H7) for all plants except Rauvolfia vomitoria and Plumbago zeylanica. Three of the medicinal plants altered at least three of the normal biochemical characteristics thus demonstrating mutagenic potentials. The results of internationally accepted Allium cepa were comparable with the modified Ames test. However, a long term in vivo and dose dependent study should be carried out to validate these results and the findings should be communicated to drug and food regulatory body and also to the general public.