Potato peel waste, with the annual production of 70,000 tons worldwide, is a burden to the agriculture with insufficient utilization. However, potato peel wastes contain some valuable components which can modulate postprandial glycemic response that would benefit the management of some high glycemia related health concerns (e.g. Type II diabetes). Our objective was to examine the influence of potato peels on starch digestive enzymes, α-amylase and mucosal α-glucosidase, in an in vitro system and investigate its inhibition mechanism. Potato peels obtained from the industry were freeze-dried, grounded and extracted with water according to our preliminary studies. Maltose and soluble starch were used as the substrates and digestive enzymes were extracted and purified from rat small intestine. The inhibition efficacy was evaluated by quantifying the released glucose using an enzymatic assay. Lineweaver-Burk plots were constructed to study inhibition kinetics and mechanism and multiple linear regression was performed to determine the significance of enzyme inhibition from different inhibitor sources. The composition of potato peel extract, including dietary fiber, minerals, and calystegine (a known inhibitor of α-glucosidase in potato peels) were characterized and quantified. Our data showed that potato peel extract decreased the activity of both α-amylase and α-glucosidase with a mixture of competitive inhibition contributed by calystegine (i.e. A3 and B2 isoforms), and non-competitive inhibition provided by some minerals. Furthermore, pectin, the major soluble dietary fiber in potato, interfered the binding capacity of both enzymes to the substrate and decreased the glucogenesis. Our research revealed that potato peel extract interfered the activities of α-amylase that hydrolyzed starch to small molecules and mucosal α-amylase that functions as a gatekeeper of glucogenesis. These findings lead to developing a new strategy to modulate starch digestion from an agricultural approach and provide a novel solution to utilize potato peels for promoting the crop sustainability.

Inhibitory effect of aqueous extract of the potato peel waste on starch digestive enzymes

255th National Meeting (2018)

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