Strawberry Anthocyanins Are Recovered in Urine as Glucuro- and Sulfoconjugates in Humans

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Abstract
Anthocyanins are phenolic compounds widely distributed in fruits and vegetables. Their consumption has been shown to prevent some chronic diseases. Anthocyanin metabolism, however, is still not fully understood. The aim of this work was to evaluate the bioavailability of anthocyanins in humans consuming a meal containing strawberries and to identify possible metabolites in urine. Six healthy volunteers (three women and three men) consumed a meal containing 200 g strawberries (providing 179 μmol pelargonidin-3-glucoside). Urine samples were collected before and after the meal and rapidly treated by solid-phase extraction. Identification and quantification of anthocyanin metabolites were carried out by HPLC-ESI-MS-MS and HPLC with UV-visible detection, respectively. In addition to pelargonidin-3-glucoside, five anthocyanin metabolites were identified in urine: three monoglucuronides of pelargonidin, one sulfoconjugate of pelargonidin and pelargonidin itself. Total urinary excretion of strawberry anthocyanin metabolites corresponded to 1.80 ± 0.29% (mean ± sem, n = 6) of pelargonidin-3-glucoside ingested. More than 80% of this excretion was related to a monoglucuronide. Four hours after the meal, more than two-thirds of anthocyanin metabolites had been excreted, although urinary excretion of the metabolites continued until the end of the 24-h experiment. This study demonstrated that anthocyanins were glucuro- and sulfo-conjugated in humans and that the main metabolite of strawberry anthocyanins in human urine was a monoglucuronide of pelargonidin.