Antimicrobial activities of Dilobeia thouarsii Roemer and Schulte, a traditional medicinal plant from Madagascar

Abstract

The leaves of Dilobeia thouarsii (Roemer and Schulte), a tree that is endemic to Madagascar (Proteaceae), are used in traditional Malagasy medicine to treat bacterial skin infections and wounds. This study investigated the in vitro antibacterial activities of D. thouarsii leaf extracts and identified the bioactive compounds with the aim of providing a scientific basis for its use against skin diseases. Using broth microdilution method for leaf crude extract and its compounds, we investigated inhibition of the growth of Bacillus cereus, Bacillus megaterium, Staphylococcus aureus, Enterococcus faecalis, Vibrio harveyi, Vibrio fisheri, Salmonella Typhimurium, Salmonella antarctica, Escherichia coli, and Klebsiella pneumoniae. The two purified phenolic compounds from leaf ethyl acetate extracts (1, 2) were found to be more active than the crude extract itself. The structure of the two compounds was elucidated by NMR and mass spectrometry: compound 1 was identified as 4-aminophenol and compound 2 as 4-hydroxybenzaldehyde. A marked inhibitory effect (MIC.. 1. mg/ml). To conclude, the high antimicrobial activity of D. thouarsii leaf extracts against S. aureus supports its traditional use to treat skin infections. © 2013 South African Association of Botanists.