Antileishmaniasis and phytotoxicity of the methanolic extracts of the stem and leaves of three Nigerian medicinal Acalypha species namely: Acalypha hispida, Acalypha torta and Acalypha wilkesiana was evaluated in vitro, as part of the screening of ethno - medically useful plants from the Nigerian flora as source for bioactive compounds. Leishmaniasis has received increasing attention in developed countries because of the growing number of cases seen in AIDS patients. Prevalent drugs not only have several adverse effects but drug resistance and treatment failures are becoming increasingly common especially in immuno-compromised patients who often fail to respond or relapse. There is thus, still need for development of new drugs. It has also been observed that bioactive and natural antitumor compounds can inhibit the growth of Lemna minor. The antileishmanial activity was assessed using promastigote culture of Pakistani leishmanial strain (L. major) in 96 well micro titer plate bioassay and phytotoxicity using the Lemna bioassay. The leaf extract of A. torta exhibited dose dependent phytotoxicity with significant phytotoxicity at the highest dose investigated. The leaf extract of A. hispida and the stem extract of A. wilkesiana also gave significant phytotoxicity at a high concenteration. The leaf extract of A. wilkesiana and the stem extract of A.torta on the other hand, displayed only moderate phytotoxicity at the highest dose studied. Only the leaf extract of A. hispida was found to be leishmanicidal with an IC50 of 71.75 μg ml-1. All the other extracts tested were not leishmanicidal. These results are indicative of the presence of bioactive compounds in these plants and could be considered a valuable support of the ethno medicinal uses of these plants.
