Traditional medicine is widely practiced in Ethiopia. Here we investigate the toxicity of extracts of seven medicinal plants traditionally used to treat breast cancer in Ethiopia. These plants, Sideroxylon oxyacanthum, Zanthoxylum chalybeum, Clematis simensis, Clematis longicauda, Dovyalis abyssinica, Vernonia leopoldi, and Clerodendrum myricoides, were selected based on recommendations by traditional healers and on the frequency of use. After harvesting the plant material, the water content was determined and the powder was subjected to methanol extraction resulting in crude extracts which were tested for cytotoxicity in dose response assay. Then the methanol extract of the most toxic plants was subjected to further solvent-solvent fractionation to gain petroleum ether, hexane, chloroform, ethyl acetate, and water fractions and these were also tested for cytotoxicity in dose response assays. Extracts of Z. chalybeum and C. myricoides were not toxic. The crude extracts of S. oxyacanthum, C. simensis, and D. abyssinica showed cytotoxicity with half maximal inhibitory concentration 50% (IC50) below 1 μg/ml in the human breast cancer cell lines JIMT-1, MCF-7, and HCC1937. The ethyl acetate fraction of V. leopoldi was the most cytotoxic fraction of all fractions tested with an IC50 of 0.87 μg/ml in JIMT-1 cells. The aqueous fraction of S. oxyacanthum and the chloroform fraction of C. simensis were also cytotoxic. In conclusion, our data show a wide difference in in vitro toxicity of medicinal plants used to treat breast cancer patients, which may guide the use of traditional medicine and the choice of plants for isolation of new compounds for cancer treatment.
Key words: Cancer, Ethiopia, in vitro cytotoxicity, 3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide (MTT), traditional medicine.
DMSO, Dimethyl sulfoxide; FBS, fetal bovine serum; IC50, half maximal inhibitory concentration 50%; MTT, 3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide; PDT, population doubling time; TM, traditional medicine.
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