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

Vahinalahaja Razafintsalama (1) , Samira Sarter (2) , Lengo Angèle Mambu (3) , Ranjana Randrianarivo (1) , Thomas Petit (4) , Jean F. Rajaonarison (5) , Christian Mertz (2) , Danielle Rakoto (1) , Victor Jeannoda (1)

1 MCAM - Molécules de Communication et Adaptation des Micro-Organismes
2 Université d'Antananarivo
3 UMR Qualisud - Démarche intégrée pour l'obtention d'aliments de qualité
4 LCSNSA - Laboratoire de Chimie des Substances Naturelles et des Sciences des Aliments
5 Département de Biochimie Fondamentale et Appliquée

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 < 0.1 mg/ml) was found against S. aureus, which is a major agent in skin infections. We observed moderate activities (MIC values of between 0.1 and 0.5 mg/ml) for E. faecalis, Vibrio spp., and Bacillus spp. Neither compound was active against Salmonella spp., E. coli and K. pneumoniae (MICs > 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.

Domaines: Chimie

Vahinalahaja Razafintsalama, Samira Sarter, Lengo Angèle Mambu, Ranjana Randrianarivo, Thomas Petit, et al.. Antimicrobial activities of Dilobeia thouarsii Roemer and Schulte, a traditional medicinal plant from Madagascar. South African Journal of Botany, 2013, 87, pp.1--3. ⟨10.1016/j.sajb.2013.02.171⟩. ⟨hal-01188116⟩