Antimicrobial activity of extracts and a germacranolidetype sesquiterpene lactone from Tithonia diversifolia leaf extract

Abstract

The in vitro antimicrobial activity of the hexane, ethyl acetate and methanol extracts of the leaf of Tithonia diversifolia, and one sesquiterpene lactone 1 isolated from the ethyl acetate extract was studied. Of the fourteen strains of bacteria used, the ethyl acetate extract was the most active, showing inhibitory activity against five Gram +ve and two Gram ‐ve organisms. This was followed by the hexane extract and then methanol. The ethyl acetate fractions (TDE 2 ‐ TDE 5, TDE 7, TDE 8 and TDE 10) showed varying degrees of inhibitory activity. The sesquiterpene lactone 1 showed activity against all the tested microorganisms, except Staphylococcus aureus and Bacillus cereus (MICs = 15.6 ‐ 62.5 μg/ml for most stains). All the extracts, fractions and compound 1 showed activity against the fungus Candida albicans. The results of the present study indicate that the non-polar leaf extract of T. diversifolia could be useful in the treatment of some disease conditions and the sesquiterpene lactone 1 could be a good candidate as a phytotherapeutic agent against some bacterial infections.