In search of antitrypanosomal compounds from medicinal plant, dried fruits of Piper nigrum (Black pepper)were extracted with methanolic solvent at concentrations (250-1000 μg ml-1). The methanolic plant extract (MPE) obtained was tested against Trypanosoma evansi for trypanocidal activity. This was carried out on Vero cells grown in Dulbecco's Modified Eagle Medium (DMEM) and supplemented with foetal calf serum (FCS) 20-40% at appropriate conditions. In vitro cytotoxicity test of P, nigrum fruitsextract at concentrations (1.56-100 μg ml-1) was done on Vero cells but without FCS. In vitro trypanocidal activity varied from immobilization, reduction and to the killing of trypanosomes in corresponding ELISA plate wells. At 750 μg ml-1of MPE, there was reduction of average mean trypanosomes count in extract as observed. At 1000 μg ml-1 of the test extract of P. Nigrum, there was complete killing of trypanosomes at 7 h of incubation. Trypanosomes counts decreased in concentration and time –dependent manner with significant difference (P<0.05). MPE of P, nigrum and diminazine aceturate, standard drug, were cytotoxic to Vero cells except at concentrations of 1.56-3.13 and 1.56-6. 25 μg ml-1. Moderate anti-trypanosmal activity of MPE of P. nigrum was observed.
Key words: Piper nigrum (fruits), trypanocidal activity, in vitro cytotoxicity test