Protocatechuic acid is not the major metabolite in rat blood plasma after oral administration of cyanidin 3-O-β-d-glucopyranoside

In this study, the formation of protocatechuic acid (PCA) as a degradation product of cyanidin 3-O-β-d-glucopyranoside (Cy3G) was evaluated in plasma after oral or intravenous administration of Cy3G in rats for better understanding of functionality of anthocyanins in vivo. Cy3G (100 mg/kg) was orally administered to rats and the blood was obtained time dependently. The plasma concentration of Cy3G and PCA was determined by high performance liquid chromatography. Cy3G was detected in rat blood plasma 15 min after oral administration and reached its maximum of 0.23 μM. Several metabolites reported in our previous studies were also observed at similar plasma levels. However, PCA was not detected in any rats at any time point, which indicates the formation of PCA from Cy3G is not a major pathway. Further, PCA was not detected in the blood plasma after intravenous administration of Cy3G. These results demonstrated that neither PCA was absorbed as the major intestinal metabolite of Cy3G after oral administration nor formed as the metabolite in liver and thus PCA does not exhibit high contribution to the functionality of Cy3G in vivo.