Leishmanicidal activity expressed in vitro by some Nepalese medicinal plants against Leishmania donovani

Abstract

Leishmanicidal activity expressed in vitro by some Nepalese medicinal plants against Leishmania donovani Visceral leishmaniasis (VL), a neglected tropical disease, affects millions of peopleworldwide especially in the developing nations. Owing to the limited and toxic chemotherapeutic interventions, there is a greater interest in new drug developments against VL, particularly from plants with unparalleled diversity in phytocompounds and bioactivity. The aim of this study was to evaluate the in vitro anti-leishmanial activity of five traditionally used Nepalese medicinal plants, namely Boerhavia diffusa (Nyctaginaceae), Calotropis procera (Asclepiadaceae), Phyllanthus niruri (Euphorbiaceae), Hedychium spicatum (Zingiberaceae), and Woodfordia fruticosa (Lythraceae) selected on the basis of their ethnomedical use in the treatment of various liver diseases and conditions such as hepatospenomegaly, a hallmark of VL. The crude ethanolic extract of W. fruticosa flowers displayed the maximum efficacy with IC 150 valuesof 35.30 ± 2.43 µg/mL against the promastigotes and 27.25 ± 1.88 µg/mL against the axenic amastigotes of Leishmania donovani. The parasites were also significantly inhibited by other three plants namely P. niruri (IC50 for promastigote = 67.46 ± 3.03µg/mL and IC 50 for amastigote = 40.23 ± 2.23 µg/mL), H. spicatum (IC50 for promastigote'= 73.63 ± 4.34 µg/mL and IC 50 for amastigote = 46.96 ± 2.11 µg/mL) and C. procera (IC 50for promastigote = 96.32 ± 8.79 µg/mL and IC50for amastigote = 57.96 ± 0.13 µg/mL). Time dependent efficacy evaluation of the extracts resulted in inhibition greater than 99% over 96 hours. The reference drugs (Miltefosine and Amphotericin B) used, though better in activity were found to be highly toxic. On the other hand, cytotoxicity tests revealed the overall safety of the extracts, the extract of W. fruticosa being the most safe (selectivity indices of 2.56 and 3.31 against promastigotes and amastigotes respectively). An antibacterial screening conducted in parallel indicated a selective action towards the parasites. Both the antibacterial and cytotoxicity tests suggested that the leishmanicidal efficacy of the extracts was not due to in vitro It is important to point out that all five investigated plant species have never been evaluated before for their antileishmanial potential and focuses on the need of such screening works. Keywords: Visceral leishmaniasis, Leishmania donovani, medicinal plants, antileishmanial, IC 50 Cytotoxicity, NepaL