Bioavailability of strawberry antioxidants in human subjects

Strawberries contain many antioxidant phytochemicals such as vitamin C, carotenoids and phenolic compounds including anthocyanins (ACN). In the present study, antioxidant composition of fresh strawberries (FS) and stored strawberries (SS) and the bioavailability of the main strawberry bioactive compounds were determined in human subjects. Thirteen healthy volunteers consumed 300g of FS and SS on two separate occasions. Blood, before and at different time points from meal consumption, as well as 24h urine, was collected, and parent compounds and metabolites of the different compounds were determined by HPLC or LC/MS/MS. A reduction in -carotene plasma concentrations v. baseline values was recorded after the consumption of FS, although the amount of this carotenoid was higher in the SS. On the contrary, a significant increase of plasma vitamin C after 2, 3 and 5h (P<005) of FS and SS consumption was recorded. No quercetin and ACN were found in plasma, while coumaric acid, 4-hydroxybenzoic acid (4HBA, 56 and 54% of pelargonidin-3- glucoside (Pel-glc) ingested with FS and SS, respectively) and protocatechuic acid (59 and 34% of cyanidin-3-glucoside ingested with FS and SS, respectively) over 8h from strawberry consumption were retrieved in the plasma. Pelargonidin glucuronide, pelargonidin glucoside and pelargonidin aglycone peaked in urine within 2h of strawberry consumption, and the 24h amount excreted was always approximately 09% of the Pel-glc dose ingested. The data indicated that the content of phytochemicals in strawberries may influence the bioavailability of individual compounds. Furthermore, in the present study, the metabolism of Pel-glc was elucidated, and, for the first time, 4HBA was suggested to be a major human metabolite of Pel-glc.