Anthocyanins as inhibitors of α-glucosidase and pancreatic lipase activity

Abstract

Food components providing glucose and fat-lowering effects in the body can be useful to attenuate the negative health effects associated to high-carbohydrates and/or high-fat diets. Here, anthocyanins were studied as potential inhibitors of α-glucosidase (α-G) and pancreatic lipase (PL) activities, two key enzymes responsible for carbohydrates and fats digestion. The anthocyanin profile of extracts obtained from bilberry (BB), blackcurrant (BC) and black rice (BR) was characterized. The capacity of extracts, pure anthocyanins, and mixtures (representative of anthocyanin extracts composition) to inhibit the activity of α-G and PL was evaluated using enzymatic assays, including acarbose and orlistat as positive controls for α-G and PL, respectively. In a concentration range of 20-320 μg/ mL, extracts showed a dose-dependent inhibitory effects on α-G activity. The calculated IC50 were 87 ± 7, 76 ± 7 and 236 ± 25 μg/mL for BB, BC and BR, respectively. Some pure anthocyanins showed inhibitory actions (cyanidin-3-O-glucoside˃delphinidin-3-O-glucoside˃petunidin-3-O-glucoside) whereas the mixtures were ineffective at the assayed range concentration. In a broader concentration range (0-2000 μg/mL), extracts did not show significant inhibition on porcine PL activity, but most of the pure anthocyanins were effective (petunidin-3-O-glucoside˃cyanidin-3-O-glucoside˃delphinidin-3-O-glucoside˃malvidin-3-O-glucoside). No inhibition was observed for peonidin-3-O-glucoside and mixtures of compounds. In summary, anthocyanins would contribute only marginally to the in vitro α-G inhibition. Regarding PL activity, their inhibitory capacity was reduced when present in extracts or mixtures, suggesting complex interactions with other components under the in vitro used conditions. In vivo studies are needed to confirm the effects of extracts/ pure anthocyanins on enzymatic activities observed here.