Isolation of an antibacterial sesquiterpenoid from Warburgia salutaris

The bark of Warburgia salutaris is used in traditional medicine as an expec torant and smoked for coughs and colds, including a topical application for sores and inflammation. A previous screening of South African medicinal pl ants showed that this plant had;promising antibacterial activity. Subsequen tly, this endangered tree species was selected for bioassay-guided fraction ation in order to identify the active principles. Fractionation of the ethy l acetate extract of the stem bark by chromatographic techniques yielded a sesquiterpenoid which exhibited antimicrobial activity against Gram-positiv e bacteria. The compound, muzigadial, has previously been reported in two o ther Warburgia species, this being the first time it has been reported from W. salutaris. Muzigadial had minimum inhibitory concentration values rangi ng from 12.5 to 100 mug ml(-1). (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.