Contents and antibacterial activity of flavonoids extracted from leaves of Psidium guajava

Abstract

Four antibacterial flavonoids (morin-3-O-lyxoside, morin-3-O-arabinoside, quercetin, and quercetin-3-O-arabinoside) were isolated from fresh and driedPsidium guajava leaves, and their concentrations were determined. Among them, quercetin and morin-3-O-arabinoside were the most and the least abundant, respectively. Studies on inhibitory effects of the flavonoids on spoilage and foodborne pathogenic bacteria revealed that they had bacteriostatic mode of action against all tested spoilage and foodborne pathogenic bacteria includingBacillus stearothermophilus, Brochothrix thermosphacta, Escherichia coliO157:H7, Listeria monocytogenes, Pseudomonas fluorescens, Salmonella enterica, Staphylococcus aureus and Vibrio cholerae.   Key words: Antibacterial activity, flavonoids, guava, Psidium guajava.