Antibacterial activity of plant extracts from azuki beans (Vigna angularis) in vitro.

This study was undertaken to examine the antimicrobial property of azuki beans (Vigna angularis). The water extracts of green, black and red colored azuki beans showed antibacterial effects against Staphylococcus aureus, Aeromonas hydrophila and Vibrio parahaemolyticus. In contrast, the extract of white azuki beans showed no inhibition towards any of the microorganisms examined. The extracts of colored azuki beans contained larger amounts of polyphenols including proanthocyanidins than the extracts of white azuki beans. The counts of S. aureus cells, inoculated in the medium containing the extracts of colored azuki beans, were significantly reduced in comparison with those of control and white azuki beans after 24 h (p < 0.05). These results suggest that polyphenols including proanthocyanidins in colored azuki beans may be responsible for their antibacterial activity.