Abstract
Inhibiting α-glucosidase activity is important in controlling postprandial hyperglycemia and, thus, helping to manage type-2 diabetes mellitus (T2DM). In the present study, free polyphenols (FPE) and bound polyphenols (BPE) were extracted from red quinoa and their inhibitory effects on α-glucosidase and postprandial glucose, as well as related mechanisms, were investigated. HPLC-MS analysis showed that the components of FPE and BPE were different. FPE was mainly composed of hydroxybenzoic acid and its derivatives, while BPE was mainly composed of ferulic acid and its derivatives. BPE exhibited stronger DPPH and ABTS antioxidant activities, and had a lower IC50 (10.295 mg/mL) value in inhibiting α-glucosidase activity. The inhibition kinetic mode analysis revealed that FPE and BPE inhibited α-glucosidase in a non-competitive mode and an uncompetitive mode, respectively. Furthermore, compared to FPE, BPE delayed starch digestion more effectively. BPE at 50 mg/kg reduced postprandial glucose increases comparably to acarbose at 20 mg/kg in ICR mice. These results could provide perspectives on the potential of BPE from red quinoa, as a functional food, to inhibit α-glucosidase activity, delay postprandial glucose increases and manage T2DM.
Highlights
According to the World Health Organization, the number of people with diabetes rose from 108 million in 1980 to 422 million in 2014
The results of the Folin–Ciocalteu assay showed that the total polyphenols content (TPC) of free polyphenols extract (FPE) and bound polyphenols extract (BPE) were 1.710 ± 0.031 mg gallic acid equivalents (GAE)/g and
Alkaline and acid treatment released a large amount of bound polyphenols from red quinoa, and BPE showed higher levels of TPC and total flavonoids content (TFC) than those of FPE
Summary
According to the World Health Organization, the number of people with diabetes rose from 108 million in 1980 to 422 million in 2014. In 2019, an estimated 1.5 million deaths were directly caused by diabetes [1]. Glycemic control is considered as an effective way to manage T2DM, and prolonged carbohydrate digestion is beneficial for T2DM patients. Inhibiting α-glucosidase activity serves as an effective strategy in delaying the digestion of carbohydrate in the gut and reducing the postprandial blood glucose peak [2]. Some clinical drugs aimed at inhibiting the activity of α-glucosidase have been invented, such as acarbose, miglitol and voglibose. Long-term use of clinical α-glucosidase inhibitors often causes some side effects, such as abdominal discomfort and flatulence [3]. Natural food-derived substances with α-glucosidase inhibitory activity show superiority over some clinical drugs due to their safety and reduced risks of side effects
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