Bioavailability of phenolic compounds in grape juice cv. Autumn Royal

Abstract

The bioavailability of major phenolics in Autumn Royal grape juice was measured in 16 subjects distributed into two groups: the experimental group (n = 8 receiving 300 mL of juice) and the placebo group (n = 8 receiving 300 mL of artificial beverage). Blood was obtained before and after 30, 90, 180, and 300 min after juice or placebo intake and 24-h urine was collected. At 30 min, catechin and gallic acid levels were 3.18 ± 0.06 and 0.33 ± 0.06 nmol/mL plasma (p < 0.01), respectively. The maximal plasma levels of catechin and gallic acid observed at 180 min were 7.11 ± 0.53 and 1.56 ± 0.07 nmol/mL, respectively. After 300 min, gallic acid was not detected and only two subjects exhibited measurable levels of catechin. After juice intake, urinary catechin and gallic acid contents were significantly higher than the basal values (p < 0.001). After a regular serving of grape juice, catechin and gallic acid are bioavailable and thus potentially capable of exerting their expected biological effects.