The excretion of anthocyanins in urine following consumption of a mixed juice prepared from strawberry and red grape juice was investigated in a human intervention study. Unmetabolised anthocyanins, and glucuronide derivatives have been detected, with pelargonidin-3 glucoside metabolised into pelargonidin monoglucuronide and pelargonidin-3-glucoside monoglucuronide. The mass of urinary anthocyanins excreted in 24 h following consumption of the mixed juice (containing 21.93 mg of anthocyanins) was 144 nmol consisting of 106 nmol of anthocyanins derived from strawberries (0.32% of ingested dose) and 38 nmol derived from red grapes (0.22% of ingested dose). A higher proportion of delphinidin-3-glucoside was excreted in the unmetabolised form than less polar anthocyanins (at p ≤ 0.05). Excretion of anthocyanins peaked between 2 and 4 h following consumption of the juice. The proportion of the ingested anthocyanins excreted was not significantly different for strawberry and red grape anthocyanins despite the differences in the structures.
Keywords: anthocyanins; bioavailability; metabolites; urinary excretion.