Bound Polyphenols from Red Quinoa Prevailed over Free Polyphenols in Reducing Postprandial Blood Glucose Rises by Inhibiting α-Glucosidase Activity and Starch Digestion

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.

Glycaemia Fluctuations Improvement in Old-Age Prediabetic Subjects Consuming a Quinoa-Based Diet: A Pilot Study

“…This was probably due to the fact that, despite maintaining a similar energy intake between products consumed in the RD and the QD, quinoa has diverse nutrients that, as we have said, may imply lower glycemia [ 1 ]. Likewise, antioxidant molecules and protein nutrients are also related to the same glycemic response in the QD, as previously has been observed [ 6 , 32 , 33 ]. Conversely, carbohydrates, as we could expect, but also fats, especially monounsaturated fatty acids (MUFA), were associated with higher glucose concentrations in this diet.…”

“…Among other nutrients, phenolic compounds found in quinoa [ 2 , 3 ] show inhibitory effects on α-glucosidase and lipase activities [ 4 , 5 ] that are involved in sugar and lipid digestion in the digestive tract, respectively. Specifically, it has recently been observed that the polyphenols present in quinoa could have an effect on the reduction in postprandial blood glucose [ 6 ]. All this leads us to think that quinoa can be used to improve the profile of metabolic risk factors and help control type 2 diabetes (T2D) [ 3 , 4 , 7 ].…”

Health Beneficial Phytochemicals in Dioscorea caucasica Lipsky Leaves and Tubers and Their Inhibitory Effects on Physiologically Important Enzymes

“…However, the inhibitory activity depends on the structural peculiarities of the phenolic compounds. Recently, Zhang et al [ 61 ] reported that the fraction of bound polyphenolics of red quinoa composed mainly of ferulic acid more strongly inhibited α-glucosidase than the fraction of free polyphenolics consisting mainly of hydroxybenzoic acid and its derivatives; the former fraction inhibited α-glucosidase in an uncompetitive mode, while the latter one in a non-competitive mode. This was explained by the peculiarities of the interactions between ferulic acid and enzyme amino acid sites.…”

Microwaving released more polyphenols from black quinoa grains with hypoglycemic effects compared with traditional cooking methods

“…8 Other than these nutrients, quinoa also contain rich healthbeneficial phytochemicals including polyphenols, saponins and phytosterols, etc. 9,10 Although some previous studies have reported the effects of cooking methods on fruits and vegetables, 2,5,11 studies about the comparison and effects of cooking methods on the polyphenols of quinoa in terms of their activities are yet to be seen. Thus, the present study used boiling, roasting and microwaving to cook black quinoa grains and extracted polyphenols from them.…”

“…Quinoa has attracted increasing attention due to its nutritional features, such as rich fiber, vitamins, minerals and balanced essential amino acids 8 . Other than these nutrients, quinoa also contain rich health‐beneficial phytochemicals including polyphenols, saponins and phytosterols, etc 9,10 . Although some previous studies have reported the effects of cooking methods on fruits and vegetables, 2,5,11 studies about the comparison and effects of cooking methods on the polyphenols of quinoa in terms of their activities are yet to be seen.…”