Bioactivity-guided fractionation has led to the successful isolation of calceolarioside A ( 1) from the methanolic extract of night jasmine leaves. The in vitro antileishmanial activity of compound 1 was determined (IC (50) = 20 microg/mL). Its IN VIVO efficacy was noted at 20 mg/kg body weight when it reduced the hepatic and splenic parasite burden by 79 and 84 %, respectively, in an established model of L. donovani Ag83 infected golden hamster. Furthermore, synergistic potentiations of compound 1 at 20 mg/kg body weight and SAG at 5 mg/kg body weight showed a significant reduction of hepatic and splenic parasite burden. No cytotoxicity was observed against the U937 cell line. This is the first report describing the isolation of compound 1 from N. arbor-tristis L. and the first demonstration of its potent activity against visceral leishmaniasis.