Bioavailability of strawberry antioxidants in human subjects

Abstract

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 300 g of FS and SS on two separate occasions. Blood, before and at different time points from meal consumption, as well as 24 h urine, was collected, and parent compounds and metabolites of the different compounds were determined by HPLC or LC/MS/MS. A reduction in a-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 5 h (P,0·05) 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 8 h from strawberry consumption were retrieved in the plasma. Pelargonidin glucuronide, pelargonidin glucoside and pelargonidin aglycone peaked in urine within 2 h of strawberry consumption, and the 24 h amount excreted was always approximately 0·9 % 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.

Berries and anthocyanins: promising functional food ingredients with postprandial glycaemia-lowering effects

“…Microbiota can degrade anthocyanins to phenolic acids and aldehydes by splitting the C-ring and modifying the remaining A and B-rings (62) . Some of the main metabolites of microbiota degradation are gallic acid, vanillic acid, homovanilic acid, protocatechuic acid (PCA), syringic acid and 4-hydroxybenzoic acid (55,(65)(66)(67)(68) . Despite knowledge of the high rate of anthocyanin degradation by gut microbiota there is still no consensus about the proportion absorbed into the systemic circulation (45,53,55) .…”

Dietary anthocyanin‐rich plants: Biochemical basis and recent progress in health benefits studies

“…These phenolic acids are thought to be formed during anthocyanin metabolic processing by enteric bacteria or in chemical reactions [20]. These anthocyanin metabolites have also been found in humans [21][22][23]. It is therefore reasonable to take into account the potential effects of such metabolites when assessing the health benefits of anthocyanins.…”

Anthocyanins as Functional Food Factors— Chemistry, Nutrition and Health Promotion —

“…Tsuda protocatechuic acid, syringic acid, vanillic acid, phloroglucinol aldehyde, phloroglucinol acid, and gallic acid, have been reported in multiple studies as anthocyanin metabolites, depending on their structure (Gonthier et al, 2003;Aura et al, 2005;He et al, 2005;Keppler and Humpf, 2005;Borges et al, 2007;Forester andWaterhouse, 2008, 2010;Avila et al, 2009). These phenolic acids are likely to be produced during anthocyanin metabolism involving enteric bacteria, or by chemical conversion, and have also been found in humans (Kahle et al, 2006;Vitaglione et al, 2007;Azzini et al, 2010). The actions of these metabolites must be taken into consideration when discussing the health benefits of anthocyanins.…”