Beninese Medicinal Plants as a Source of Antimycobacterial Agents: Bioguided Fractionation and In Vitro Activity of Alkaloids Isolated from Holarrhena floribunda Used in Traditional Treabnent of Buruli Ulcer

Abstract

Buruli ulcer (BU) imposes a serious economie burden on atfected households and on health systems that are involvcd in diagnosing the disease and treating patients. Research is needed to find cost-effective therapies for this costly disease. Plants have always been an important source of new pharmacologically active molecules. Consequently we decided to undertake the study of plants used in traditional treatment of BU in Benin and investigate their antimycobacterial activity as weil as their chemieal composition. Extracts from forty-four (44) plant species were selected on account of reported traditional uses for the treatment of BU in Benin and were assayed for antimycobacterial activities. Crude hydroethanolic extract from aerial parts ofHolarrhenafloribunda (G. Don) T. Durand and Schinz was found to have significant antimycobacterial activityagainst M. ulcerans (MIC =125 ~g/mL). We describc here the identification of four steroidal aIkaloids from Mycobacterium ulcerans growth-inhibiting fractions of the alkaloidal extract of the aerial parts of Holarrhena floribunda. Holadysamine was purified in sufficient amount to allow the determination of its MCl (=50 ~g/mL). These resuIts give sorne support to the use of this plant in traditional medicine.