Cytotoxicity of three South African medicinal plants using the Chang liver cell line
Arctotis arctotoides (Asteraceae), Gasteria bicolor (Asphodelaceae) and Pittosporum viridiflorum (Pittosporaceae) are commonly used in the Eastern Cape, South Africa by traditional healers for the treatment of opportunistic fungal infections in HIV/AIDS patients. Unfortunately, there is a dearth of published data regarding the toxicity of the selected plants, despite the fact that experimental screening of toxicity is crucial to guarantee the safety of the users. It was, therefore, decided to evaluate the cytotoxicity of the hexane and acetone extracts of the medicinal plants against the Chang liver cell line using the in vitro MTT assay. Different concentrations of the extracts were added into 24-hour cultured cells and incubated for 72 hours under specific conditions (37 °C, 5% CO2). Cell survival was evaluated using the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. Depending on the dosage and duration of treatment, the cytotoxic effects of G. bicolor and P. viridiflorum were considered relatively weak (but not entirely absent). A. arctotoides extracts were the most toxic both in terms of IC50 values as well as the steeper slope of the dose response curve. The IC50 values for the acetone and hexane extracts of this plant were 17.4 and 12.4 µg/ml respectively. Many members of the Asteraceae family (including members of the genus Arctotis) are known to exert contact dermatitis due to sesquiterpene lactones in the oleoresins found on their leaf and stem surfaces. Normally, these constituents are only allergenic on the skin and extracts of these plants are safe for ingestion. Therefore there exists the possibility that the negative reaction of the liver cells in this in vitro assay might be due to a reaction akin to contact dermatitis after the unphysiological direct contact of the liver cells to the extracts and therefore not as compromising to the traditional use of this plant as one might otherwise suppose.
Keywords: Cytotoxicity, medicinal plants, opportunistic fungal infections, Chang liver cell line