We evaluated the anti-allergic effect of black colored rice (Oryza sativa L.) and its main constituents, cyanidin 3 glucoside (C3G) and cyanidin (Cy) on scratching behavior in mice. The black rice extract (BRE) and its constituts inhibited the scratching behavior induced by compound 48/80 and histamin.
To understand the role of intestinal microflora in the anti-allergic effect of C3G, which was suspected to play a key role in depressing scratching behavior, C3G was incubated with human fecal bacteria. Protocatechuic acid (PCA) was found within the 30 min and its concetration sharply increased. Vanillic acid (VA) was also detected in the incubated sample mixture. The anti-allergic effect of these compounds, C3G, Cy, PCA and VA, were investigated. PCA and Cy potentely reduced scratching behavior in mice induced by compound 48/80 and histamin.
These findings enable us to conclude that intestinal bacterial metabolites, PCA and VA, produced by intestinal micro flora contributed to suppressing the scratching behavior induced by compound 48/80 and histamin.