Anti-Proliferative Effects of Plant Extracts from Zimbabwean Medicinal Plants against Human Leukaemia Cell Lines

A selected group of 14 medicinal plants was screened for antiproliferative activity against two human leukaemia cell lines Jurkat T and Wil 2 in vitro. The Trypan Blue assay was used to assess antiproliferative and cytotoxic activity. The five most potent medicinal plants showed the following order of potency against Wil 2 cell line: Parinari curatellifolia > Aloe barbadensis > Croton gratissimus > Syzigium guineense > Vernonia adoensis with IG50s of 93, 115, 148, 149.8 and 130 μg/ml, respectively. The plants had comparable proliferation inhibition to the cancer drug doxorubicin. From these species, high levels of cytotoxicity were detected in extracts from Parinari curatellifolia and Aloe barbadensis to Wil 2 cell line at concentrations of 500 and 1 000 μg/ml. Croton gratissimus, Syzigium guineense and Vernonia adoensis extracts were found to be antiproliferative and not cytotoxic at the same concentrations. P. curatellifolia extract at a concentration of 10 μg/ml reduced cell proliferation of Jurkat T cells by 70% after 48 h of incubation. Studies were also carried out where the extract from P. curatellifolia combined with doxorubicin at concentrations 10 to 0.50 μg/ml were tested for antiproliferative activity against a Jurkat T cell line. The top five plant extracts had IG50s of less than 150 μg/ml. The results show that plants used traditionally for treatment of diseases such as tuberculosis, mycosis and diarrhea can be used to inhibit cell proliferation in leukaemia cell lines. The extract from P. curatellifolia could be a potential source of lead compounds that may be used as anticancer drugs. The plant extracts that showed cytotoxicity and inhibition of cell growth will be further characterized to identify the active fractions and compounds. _____________________________________________________________________________________________________________