Abstract
Extracts and fractions of some Ochna species had excellent antibacterial activity. Before considering the potential therapeutic use of these extracts it is important to determine the safety of extracts. The cytotoxicity of Ochna natalitia, Ochna pretoriensis, Ochna pulchra, Ochna gamostigmata, and Ochna serrulata (Ochnaceae) was determined in monkey kidney (Vero) cells, human hepatocellular carcinoma (C3A) cells and bovine dermis cells using the mitochondrial viability MTT assay. Their potential mutagenic effects were also determined using the Ames test with strains Salmonella typhimurium TA98 and TA100 with and without metabolic activation. The LC50 values (the lethal concentration at which 50% of the cells are killed) of the extracts on the various cell lines ranged from 26 to 99μg/ml. None of the plant species was mutagenic (mutagenic index values≤1.59 for TA98 and ≤0.92 for TA100). In a previous study, we determined the antibacterial activity of the five extracts against Staphylococcus aureus, Escherichia coli, Enterococcus faecalis and Pseudomonas aeruginosa. From this we calculated the selectivity index (SI) values by dividing the LC50 value by the minimum inhibitory concentration (MIC) to obtain the ratio of toxicity to bioactivity of each extract. The plant extracts had low SI values≤1.307. This is a clear indication of non-selective toxicity, i.e. extracts are almost equally toxic to the bacteria and mammalian cell lines used in the assays. As a result, the extracts may have limited application as ingestible or intravenous therapeutic agents based on the in vitro findings. However, it may be necessary to also evaluate in vivo toxicity of the extracts in animal models as in vitro toxicity does not always equate to in vivo toxicity because of the difference in physiological microenvironment in live animals and tissue culture. Additionally, if it is the case that the toxic compounds are not the same as the active compounds, it may be possible to potentiate the extracts by the removal of toxic compounds and concentration of active compounds. The extracts may then be useful for development into treatments for topical bacterial infections.
Highlights
The reliance on medicinal plants as an alternative form of health care warrants scientific validation of their safety
It was for these reasons that we investigated the cytotoxic effects of extracts of five Ochna species
Based on the results obtained from this study, the previously reported high antibacterial activity of the five Ochna species may be a result of non-selective toxicity i.e. general toxicity
Summary
The reliance on medicinal plants as an alternative form of health care warrants scientific validation of their safety. 60-80% of the South African population relies on traditional herbal medicine for their primary health care needs (Mander, 1998). Despite the known pharmacological/therapeutic effects of traditional medicinal plants, it is crucial to validate their safety as well as their efficacy when studying their traditional uses. Medicinal plants and pharmaceutical drugs may be therapeutic at one dose and toxic at another (McGaw et al, 2007). Since extracts of medicinal plants are natural, they are safe. Plants used medicinally are sometimes assumed to be safe but many are potentially toxic (Street et al, 2008). Secondary metabolites, which are the basis of biological activity of medicinal plants, are not benign molecules. Plants have evolved many chemical defences to deter, stun, poison or kill threatening species (Gurib-Fakim, 2006)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
