Abstract
Gastrointestinal digestion (GID) is a physiological process that transforms the stability, bioaccessibility and antioxidant activity (AOX) of polyphenols from blackberries (Rubus spp.). This study aimed to investigate the effect of the INFOGEST® GID protocol on the phenolic stability, bioaccessibility and AOX of Mexican wild (WB) and commercial (CB) blackberries. After GID, the total phenolic and anthocyanin contents in blackberries decreased by ≥68% and ≥74%, respectively. More than 40 phenolics were identified during GID; most of them degraded completely during digestion. GID had a negative effect on the AOX of both fruits (>50%), but WB showed the highest antioxidant activities, as assessed by the ORAC, DPPH, reducing power and β-carotene bleaching methods. In Caco-2 cells, the cell-based antioxidant activity of digested blackberries (p < 0.05) decreased by 48% in WB and by 56% in CB. The capacity to inhibit intracellular ROS decreased by 50% in WB and by up to 86% in CB, after digestion. GID is a complex process that impacts on the bioactive properties of food nutrients, especially phenolics. In vitro and cellular AOX of WB polyphenols withstood the gastrointestinal environment better than CB phenolics. The in vitro assays results suggest that phenolics from underutilized WB have a higher bioaccessibility and antioxidant capacity than the polyphenols from the most frequently consumed CB. However, whether this corresponds to a better bioaccessibility in humans remains to be determined in future work.
Highlights
Blackberries (Rubus spp.) are a large group of fruits with a rich diversity of bioactive polyphenols, such as phenolic acids, flavonoids and tannins.[1]
The objectives of the present study were (a) to evaluate the bioaccessibility and digestive stability of each phenolic compound after Gastrointestinal digestion (GID), using the INFOGEST® 2.0 protocol; (b) to determine the in vitro antioxidant activity of wild (WB) and commercial (CB) blackberry polyphenols during GID; and (c) to assess the antioxidant potential of WB and commercial Rubus fruticosus brambles (CB) digestates based on their cellular antioxidant activity (CAA) and their capacity to inhibit the synthesis of reactive oxygen species (ROS) in the Caco-2 cell line
The oral phase is of special importance during the digestion process, since it is during this phase that the plant matrix containing phytocompounds is broken down during the chewing step, the components are exposed to the salivary fluids and to the action of α-amylase, and an anaerobic atmosphere begins
Summary
Blackberries (Rubus spp.) are a large group of fruits with a rich diversity of bioactive polyphenols, such as phenolic acids, flavonoids and tannins.[1] The phenolic profile of blackberries is closely related to biotic and abiotic stimuli, resulting in some important differences between wild species and cultivated. Different hydroxycinnamic and hydroxybenzoic acids are present in free forms, but they are mainly found as blocks of polymeric polyphenols, such as proanthocyanidins and hydrolysable tannins.[10] In contrast, flavonoid derivatives, which have a characteristic C6–C3–C6 (A, B and C rings) carbon skeleton, exhibit several patterns of hydroxylation, acylation, glycosylation and methoxylation of the main structure. These compounds are bound to macromolecules, such as proteins and peptides (linking the phenolic group of the phenol ring with the –NH group of peptides) or carbohydrates (liked by α- and β-glycosidic bonds), the dry matter content of which is about 80% and 5%, respectively.[8,16] It should be noted, that these macromolecules undergo marked degradation during GID, becoming bioavailable sugars and small peptides/amino acids.[17]
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