Antibacterial Action of Bainiku-Ekisu (Japanese Apricot Fruit Extracts), a Traditional Drug, on Vibrio parahaemolyticus and Its Organic Acid Components

Abstract

Bainiku-ekisu (Japanese Apricot Fruit Extracts) is a traditional drug in Japan and its main components were shown to be citric acid and malic acid (32% and 11% on average) by HPLC analysis of 9 commercial products. The antibacterial action of Bainiku-ekisu was investigated in vitro against one of the causative bacteria of food-borne infection, Vibrio parahaemolyticus. Addition of both Bainiku-ekisu (1%) and cholic acid (0.2%) to 2% polypepton medium with sodium chloride at about pH 7.0 decreased the viability of V. parahaemolyticus remarkably, although Bainiku-ekisu did not show the activity by itself. Citric acid is considered to be responsible for this antibacterial action with cholic acid, because we confirmed the effectiveness of citric acid but not of malic acid. The strong acidity of Bainiku-ekisu was enough to change the pH of a model intestinal solution (pH 8.03) to 6, even at 1% concentration.
Based on these results, the inhibitory effect of Bainiku-ekisu on Gram-negative and food-borne infectious bacteria in vivo is discussed.