High Throughput Screening of Extracts From Plants Used in Traditional Chinese Medicine Against Trypanosoma brucei brucei 427

Abstract

Trypanosoma brucei, the protozoan blood parasite, is the etiological agent for African trypanosomiasis (also known as "sleeping sickness"). This parasite is estimated to infect almost 30,000 people each year in central Africa, and has a 100% mortality rate if left untreated. The current drugs used to treat infection by T. brucei were developed almost a century ago. These compounds are toxic, expensive, and are becoming ineffective due to increased resistance. There are significant needs for new drug therapies for the treatment of T. brucei infections. The purpose of this study was to screen plants used in traditional Chinese medicine for activity against T. brucei. A library of 144 crude extracts from 34 different plants was screened against the trypanosomes using high throughput screening techniques and a resazurin based PrestoBlue assay. The extract cytotoxicity was also evaluated using L6 rat skeletal myoblast cells. The chloroform and water extracts of Scutellaria baicalensis showed the highest activity against the trypanosomes (IC50 of 11.43 and 19.86 μg/ml) as well as selectivity for the trypanosomes over the mammalian cells. The petroleum ether extracts of Psychotria rubra, and Elephantopus scaber, the ethyl acetate extract of Pandanus tectorius, and the extract of Belamcanda chinensis prepared with 95% ethanol all showed promising activity (IC50 of 38.02 - 49.6 μg/ml) and high selectivity. The results suggest that plants used in traditional Chinese medicine may have biochemical compounds of potential interest in the search for better drugs to treat African sleeping sickness.