Inhibitory properties of polyphenols in Malus "Winter Red" crabapple fruit on α‐glucosidase and α‐amylase using improved methods.

To explore the inhibitory activity of polyphenols on α‐glucosidase and α‐amylase, 16 polyphenols were isolated, identified, and quantified in an edible Malus "Winter Red" crabapple fruit. The limitations of two traditional methods for α‐glucosidase and α‐amylase activity assay in vitro were assayed. An improved method based on an HPLC assay for α‐glucosidase and a colorimetric method coupled with a custom‐made mini‐column for α‐amylase were established. Compared with positive controls, acarbose and miglito, most polyphenols, especially the four aglycones (cyanidin, quercetin, phloretin, and 3‐hydroxyphloretin) showed higher inhibition rates on α‐glucosidase. None of the polyphenols showed higher inhibition rates on α‐amylase than acarbose, but most, especially the four aglycones, showed higher inhibition rates on α‐amylase than miglito. The Malus Winter Red fruit has great potential for postprandial blood glucose management as a potential diet therapy for diabetic patients. [ABSTRACT FROM AUTHOR]