Isolation and identification of antimalarial substances from streptomyces culture broth

Abstract

Streptomyces sp. var. 245.1, a new isolate of Streptomyces from soil collected from Petchaboon province (northern Thailand), was used as a producer of an antimalarial substance. The antimalarial activity was determined by using the in vitro microtest technique. The crude culture broth actively inhibited the development of Plasmodium falciparum at an MIC of 1 ug/ml. It was extracted with dichloromethane and ethyl acetate consecutively. The extract was active at an MIC of 0.1 ug/ml. Cultivation of the organism was done in both small and large scales. The antimalarial substance(s) from small scale cultivation was extracted with dichloromethane and ethyl acetate and then partially purified-by preparative thin-layer chromatography (PLC). The fractions named PLC 4/S and PLC 5/S were found to possess high antimalarial activity with an MIC of 10 ng/ml. Antimalarial substance(s) from large scale cultivation was firstly extracted with dichloromethane, ethyl acetate and followed by hexane in order to get rid of antifoam. The antimalarial substance(s) was found mainly in hexane insoluble part. PLC separation of the hexane insoluble part yielded 5 prominent fractions. One of the fractions, PLC 5/F, showed very high antimalarial activity with an MIC of 1 ng/ml. It was further used for physical and chemical analyses (NMR, IR).