Inhibition of α-glucosidase activity by Morus australis fruit food

Abstract

Mulberry fruit is thought as a healthy sweetener because it contains iminosugars, such as 1deoxynojirimycin (1-DNJ), fagomine and 2-O-α-D-galactopyranosyl deoxynojirimycin (GAL-DNJ), that inhibits α-glucosidase. In this study, we quantified iminosugars and glucose concentrations in Morus australis fruit foods and analyzed their inhibitory effects against the activities of αglucosidase-related four enzymes, maltase, glucoamylase, sucrase, and isomaltase. By LC-MS/MS, the concentrations of 1-DNJ, fagomine, and GAL-DNJ of the M. australis fruit wine, juice, vinegar drink, vinegar, and jam were 1.76-32.5, 0.058-0.290, and 30.2-209 μg/mL, respectively. By highperformance anion-exchange chromatography with pulsed amperometric detection (HPAE-PAD),the glucose concentrations were 0 mg/mL for wine and 13.9-39.7 mg/mL for juice, vinegar drink, vinegar, and jam. The IC50 values of these five foods were 1.9-4.4 % v/v for maltase, 0.37-5.0 % for glucoamylase, and 0.28-1.2 % for sucrase, and 2.0% for isomaltase. Considering the 1-DNJ and glucose concentrations in these five M. australis fruit foods and the IC50 values of 1-DNJ and glucose for α-glucosidase, it was suggested that 1-DNJ is a main inhibitor for α-glucosidase in these foods, and glucose is involved in the inhibition except for wine.