Triterpenes, steroids and lichexantone from Macrolobium acaciifolium leaves and branches hexane extracts and antibacterial activity

Abstract

Macrolobium acaciifolium belongs to Fabaceae family and only few phytochemical studies were carried out in the scientific literature consulted. The objective of this work was to isolate and identify the secondary metabolites from M. acaciifolium leaves and branches hexane extracts, in addition to evaluate the antibacterial potential of the extracts. The plant materials were dried and extracted with hexane, then methanol and water. The hexane extracts showed the presence of terpenoids (including steroids) by thin layer chromatography and nuclear magnetic resonance analysis. The phytochemical fractionation allowed to isolate the triterpenes: lupeol, β-amyrin and 24-methylenecycloartanol from hexane leaves extract. The mixture of the triterpene friedelin and the xanthone 1-hydroxy-3,6-dimethoxy-8-methyl-9h-xanthen-9-one (lichexanthone) were isolated from branches hexane extract. In both extracts, the mixture of the steroids β-sitosterol and stigmasterol were also isolated. The leaves hexane extract showed to be toxic to Aeromonas hydrophila with 87% growth inhibition at a concentration of 1000 µg/mL. This is the first description of the isolation of these substances in Macrolobium acaciifolium and the antibacterial activity.