Antibacterial prenylated stilbenoids from peanut (Arachis hypogaea)
Stilbenoids are a class of secondary metabolites with a stilbene backbone that can be produced by peanut (Arachis hypogaea) as defence metabolites. Six monomeric prenylated stilbenoids, including the compound arachidin-6 (4), were isolated from extracts of fungus-elicited peanuts (Arachis hypogaea) using preparative liquid chromatography. Their structures were confirmed by MSn, HRMS and NMR spectroscopy and their antibacterial activity was evaluated against methicillin-resistant Staphylococcus aureus (MRSA). Similarly to other phenolic compounds, prenylated derivatives of stilbenoids were more active than their non-prenylated precursors piceatannol, resveratrol, and pinosylvin. Chiricanine A (6), a chain-prenylated pinosylvin derivative, was the most potent compound tested, with a minimum inhibitory concentration (MIC) of 12.5 μg mL−1. Arachidin-6 (4), a ring-prenylated piceatannol derivative, had moderate potency (MIC 50–75 μg mL−1). In conclusion, prenylated stilbenoids represent a group of potential natural antibacterials which show promising activity against MRSA.