Blackberry anthocyanins are slightly bioavailable in rats

Anthocyanins are phenolic compounds widely distributed in fruits and vegetables. Several positive effects of anthocyanin feeding have been described. We evaluated the absorption and metabolism of anthocyanins (cyanidin 3-glucoside and malvidin 3-glucoside) in rats adapted for 8 d to a diet enriched with a lyophilized blackberry powder. Rats had free access to an anthocyanin-containing diet for 8 h/d. Food was consumed throughout this period, and no anthocyanin accumulated in plasma at any of the times of sampling. Anthocyanins were recovered in urine as the intact glycosidic forms, whereas neither aglycone nor conjugates were detected. Moreover, peonidin 3-glucoside was present in urine and could have resulted from hepatic methylation at the 3' hydroxyl moiety position of cyanidin 3-glucoside. Urinary recovery of cyanidin 3-glucoside in either intact or methylated forms was approximately 0.26% of the ingested amount, whereas that of malvidin 3-glucoside was 0.67%. This result suggested that structure of the aglycone moiety of anthocyanins could play an important role in their metabolism. Low amounts of glucosides as well as of cyanidin were recovered in cecal contents. This could result from adaptation of microflora to anthocyanin degradation. Overall, these data indicate that blackberry anthocyanins are excreted in urine as intact and methylated glucoside forms and that their bioavailability is very low compared with other flavonoids.