Abstract:
BACKROUND:
Several herbs are traditionally used in the treatment of a variety of ailments
particularly in the rural areas of South Africa where herbal medicine is mainly the
source of health care system. Many of these herbs have not been assessed for safety or
toxicity to tissue or organs of the mammalian recipients.
METHODS:
This study evaluated the cytotoxicity of some medicinal plants used, inter alia, in the
treatment of diarrhoea, and stomach disorders. Six selected medicinal plants were
assessed for their antibacterial activities against ampicillin-resistant and kanamycinresistant
strains of Escherichia coli by the broth micro-dilution methods. The
cytotoxicities of methanol extracts and fractions of the six selected plants were
determined using a modified tetrazolium-based colorimetric assay (3-(4, 5-
dimethylthiazol)-2, 5-diphenyl tetrazolium bromide (MTT) assay).
RESULTS:
The average minimum inhibitory concentration (MIC) values of the plants extracts
ranged from 0.027 mg/mℓ to 2.5 mg/mℓ after 24 h of incubation. Eucomis autumnalis
and Cyathula uncinulata had the most significant biological activity with the least
MIC values. The in vitro cytotoxicity assay on human hepatocarcinoma cell line
(Huh-7) revealed that the methanol extract of E. autumnalis had the strongest
cytotoxicity with IC50 of 7.8 μg/mℓ. Ethyl acetate and butanol fractions of C.
uncinulata, Hypoxis latifolia, E. autumnalis and Lantana camara had lower cytotoxic
effects on the cancer cell lines tested with IC50 values ranging from 24.8 to 44.1
μg/mℓ; while all the fractions of Aloe arborescens and A. striatula had insignificant or
no cytotoxic effects after 72 h of treatment.
CONCLUSIONS:
Our results indicate that the methanol fraction of E. autumnalis had a profound
cytotoxic effect even though it possessed very significant antibacterial activity. This
puts a query on its safety and hence a call for caution in its usage, thus a product
being natural is not tantamount to being entirely safe.However, the antibacterial
activities and non-cytotoxic effects of A. arborescens and A. striatula validates their
continuous usage in ethnomedicine.
