Isolation and in vitro antimalarial activity of chloroform extract from Thai Picrasma javanica Bl stembark

Abstract

The in vitro antimalarial activity against Plasmodium falciparum K1 of the four extracts from the stembark of Picrasma javanica Bl, that is, water, methanol, chloroform and hexane were studied using a modification of the [³H]hypoxanthine incorporation method. It was found the chloroform extract showed in vitro antimalarial activity with IC₅₀ of 20.0 µg/ml. The extract was further isolated using acid-base solvent extraction method, yielding alkaloidal and non-alkaloidal portion. The alkaloidal portion was effective against P. falciparum with in vitro IC₅₀ of 15.0 µg/ml. The component of alkaloidal portion was determined using GC-MS technique. Mass spectrum of the major compound in alkaloidal portion corresponds to that of known antimalarial 4-methoxy-1-vinyl-B-carboline. Further purification using preparative TLC, the structure of this alkaloid was transformed to potential antimalarial Crenatine (1-ethyl-4-methoxy-B-carboline). According to the literature review data, further study should be focus on the antimalarial activity of sixteen indoalkaloids reported for this medicinal plant.

Keywords: B-carboline, antimalarial activity, Picrasma javanica Bl, 4-methoxy-1-vinyl-B-carboline, 1-ethyl-4-methoxy-B-carboline.