Protocatechuic acid is the major human metabolite of cyanidin-glucosides

Abstract

The metabolic fate of dietary anthocyanins (ACN) has not been fully clarified in humans. In all previous studies, the proportion of total ACN absorbed and excreted in urine was < 1% intake. This study aimed to elucidate the human metabolism of cyanidin-glucosides (CyG) contained in blood orange juice (BOJ). One liter of BOJ, containing 71 mg CyG, was consumed by 6 healthy, fasting volunteers. Blood, urine, and fecal samples were collected at baseline and at different times up to 24 h after juice consumption. The content of native CyG, glucuronidated/methylated derivatives, and various phenolic acids was determined by HPLC/MS/MS. The serum maximal concentration of cyanidin-3-glucoside (Cy-3-glc) was 1.9 ± 0.6 nmol/L and that of protocatechuic acid (PCA) was 492 ± 62 nmol/L at 0.5 h and 2 h after juice consumption, respectively. The calculated total amounts in plasma corresponded for Cy-3-glc to 0.02% and for PCA to 44% of CyG ingested. CyG and glucuronidated/methylated metabolites, but not PCA, were detected in urine. ACN recovered in 24-h urine collections represented ∼1.2% of the ingested dose. Both CyG (1.90 ± 0.04 nmol/g) and PCA (277 ± 0.2 nmol/g) were recovered in 24-h fecal samples. Data explained the metabolic fate of 74% of BOJ ACN. PCA was for the first time, to our knowledge, identified in humans as a CyG metabolite, accounting for almost 73% of ingested CyG. A high concentration of PCA may explain the short-term increased plasma antioxidant activity observed after intake of cyanidin-rich food and it can also contribute to the numerous health benefits attributed to dietary ACN consumption. © 2007 American Society for Nutrition.