Bioassay-guided isolation of ochrolifuanine: A bisindole alkaloid of Dyera costulata active on Trypanosoma brucei brucei

Abstract

Dyera costulata, locally known as jelutong, have shown promising in vitro inhibitory activity against Trypanosoma brucei brucei strain BS221. The methanolic leaf extract, evaluated using Alamar Blue Assay, showed strong antitrypanosomal activity (IC50 0.58 ± 0.01 µg mL-1) and high selectivity index (SI value 169.5) towards the protozoa. While, the hexane leaf extract was moderately active (IC50 4.4 ± 0.05 µg mL-1; SI value of 22.7). Total alkaloids extracted from the active methanolic fraction showed strong activity and high selectivity (IC50 0.08 ± 0.07 µg mL-1, SI value 890) towards T. b. brucei. Bioassay-guided fractionation of the total alkaloid extract yielded an active compound 1 (IC50 0.06 ± 0.03 µg mL-1, SI value 76.3). Compound 1 was identified as ochrolifuanine from the bisindole alkaloid group, based on spectral analysis (MS, 1D and 2D NMR). The presence of alkaloids in D. costulata leaves may be indicative of the various bioactivities observed in this plant. Previously, ochrolifuanine has been reported for antimalarial and antimicrobial activity. This study reports, for the first time, on the antitrypanosomal activity of ochrolifuanine from D. costulata.