Antileishmaniasis, phytotoxicity and cytotoxicity of Nigerian Euphorbiaceous Plants 2: Phyllanthus amarus and Phyllanthus muellerianus Extracts.

Methanolic extracts of the leaves of Phyllanthus amarus and stem of Phyllanthus muellerianus were studied for antileishmaniasis activity, phytotoxicity and cytotoxicity. The antileishmanial activity was evaluated in vitro using promastigote culture of Pakistani leishmanial strain (L. major) in 96 well micro titer plate bioassay, while phytotoxicity was assessed using the Lemna bioassay and cytotoxicity using brine shrimp lethality assay. Methanolic extract of stem of P. muellerianus was found to exhibit cytotoxicity with a positive lethality of LD50 4.867 µg/ml, low phytotoxicity at 100 µg /ml and significant phytotoxicity at 1000 µg/ml. It showed no anti-leishmanial activity. On the other hand, the methanolic extract of leaf of P. amarus was found to be leishmanicidal with an IC50 of 78.27 µg/ml, low phytotoxicity at 1000 µg /ml and no cytotoxic activity. Bioactive compounds are often toxic to Artemia salina (shrimp eggs) and it has been observed that natural antitumor compounds can inhibit the growth of Lemna minor. The higher cytotoxicity exhibited by P. muellerianus when compared with the standard drug, etoposide used (LD50 7.4605 µg/ml) as well as the good anti-leishmanial activity displayed by P. amarus justifies their ethno-medicinal uses and is suggestive of the presence of physiologically active natural products in both plants.