Cranberry leaves (Vaccinium macrocarpon) as a source of antimicrobial metabolites

Abstract

Secondary metabolites from the leaves of North American cranberry (Vaccinium macrocarpon) are under investigation for structure and inhibitory activity against bacterial biofilm formation and cancer cell growth. Compounds were separated by column chromatography using various stationary phases, and characterized by MS and NMR. In addition to several quercetin glycosides, proanthocyanidin subfractions ranging in oligomer size from dimer to octamers, were isolated from the aqueous extracts and characterized by MALDI-TOF MS. Cranberry leaf PACs inhibited biofilm formation by Staphylococcus aureus (MBIC=1.5–3.1µg/mL) as well as the growth of several Candida species and HeLa cells. The quercetin glycosides also inhibited S. aureus biofilms (MBIC=25µg/mL). Constituents of the nonpolar extracts include β-sitosterol and ursolic acid derivatives to be identified. Cranberry leaves may be a useful source of antimicrobial compounds.