Cytotoxicity and mutagenicity investigation of extracts of common South African ethnoveterinary plants

Rural livestock keepers in southern Africa have access to an extraordinary diversity of plants to provide treatments for various diseases in their animals, particularly infections and wounds. Many of these plants have been shown in our previous studies to possess promising antibacterial, antifungal and antiviral properties, but have rarely been investigated for toxicity. Cytotoxic and genotoxic effects of acetone extracts of sixteen plants used widely in South African ethnoveterinary medicine (EVM) were studied. Cytotoxicity was determined against Vero kidney cells and bovine dermis cells using various assays. Mutagenic effects were investigated using the Ames test with Salmonella typhimurium strains TA98 and TA100. Bovine dermis cells were generally more sensitive to the extracts than Vero cells. Combretum caffrum was the most cytotoxic, with LC50 less than 50 ug/ml against both cell types. Markhamia zanzibarica was also fairly cytotoxic, but most of the plant extracts had LC50 values between 0.1 and 1mg/ml. Sclerocarya birrea was not cytotoxic to the cell lines up to the highest test concentration of 1mg/ml. None of the plant extracts exhibited mutagenic effects against the strains tested. Obtaining an indication of toxicity of ethnoveterinary plant extracts aids in the selection of plants for isolation studies of anti-infective compounds lacking non-specific toxicity. These studies also provide useful indications of toxicity of presently used traditional remedies particularly in the case of topical applications, bearing in mind the limitations of in vitro tests.