Bioavailability of Anthocyanin Cyanidin-3-Glucoside from Black Rice (<i>Oryza sativa</i> L.) Extract after Co-Administration with Allyl Isothiocyanate in Rats

Black rice (BR) is beneficial for the health of animals and humans. Herein, we investigated the pharmacokinetics of cyanidin-3-glucoside (C3G), a major anthocyanin constituent of BR, in male rats. After its intravenous administration, C3G was rapidly distributed throughout the body and disappeared from the plasma. Its cumulative urinary excretion accounted for less than 20% of the dose administered. After a single dose of BR extract (C3G40) containing C3G was orally administered (300 mg C3G/kg body weight), the C3G plasma concentration peaked at 30 min and then rapidly declined within 4 h. The extent of the cumulative urinary excretion of C3G, together with the area under the curve (AUC) of the plasma C3G concentration, indicated a bioavailability of approximately 0.5-1.5%. These results suggest that C3G was rapidly absorbed from the gastrointestinal tract in rats; however, its plasma concentration was very low. We also examined the enhancing effect of allyl isothiocyanate (AITC), a pungent component of wasabi, on the gastrointestinal absorption of C3G in rats. Following the co-administration of C3G with AITC dissolved in PEG200, the urinary excretion and AUC of C3G were 4.5- and 2.7-fold higher than those in the control group (without AITC) (p<0.01), respectively. This is the first study to show that the gastrointestinal absorption of BR anthocyanins is promoted by AITC.