Inhibition of α‐amylase and α‐glucosidase by Morus australis fruit extract and its components iminosugar, anthocyanin, and glucose

Abstract

The inhibition of α‐amylase and α‐glucosidase are important for the maintenance of blood glucose level. Mammalian α‐glucosidase includes maltase–glucoamylase and sucrase–isomaltase complexes. In this study, we examined the inhibitory effects of Morus australis fruit extract and its components, that is, three iminosugars (1‐deoxynojirimycin [1‐DNJ], fagomine, and 2‐O‐α‐D‐galactopyranosyl deoxynojirimycin), two anthocyanins (cyanidin‐3‐glucoside and cyanidin‐3‐rutinoside), and glucose, against α‐amylase and α‐glucosidase. We also quantified the concentration of each component in M. australis fruit extract. The IC50 values of the fruit extracts of four M. australis subspecies were >10 mg/ml for α‐amylase, 1.1–1.7 mg/ml for maltase, 6.9–8.6 mg/ml for glucoamylase, 0.13–1.0 mg/ml for sucrase, and 0.46–1.4 mg/ml for isomaltase. When the IC50 value of each component and the concentration of each component in the fruit extract were taken into consideration, our results indicated that glucose are involved in the inhibition of α‐amylase, and 1‐DNJ and glucose are involved in the inhibition of α‐glucosidase. This is in contrast to that in M. australis leaf, neither anthocyanin nor glucose are contained, and 1‐DNJ is a main inhibitor. Practical Application It is widely accepted that inhibition of α‐amylase and α‐glucosidase is one of the strategies to treat type‐2 diabetes. Today, acarbose, miglitol, and voglibose are clinically used for this purpose. Our results that 1‐DNJ and anthocyanin are present in Morus australis fruit and are involved in the inhibition of α‐amylase and α‐glucosidase suggest that M. australis fruit is a healthy sweetener.

A Basic Study of the Effects of Mulberry Leaf Administration to Healthy C57BL/6 Mice on Gut Microbiota and Metabolites

“…First, the presence of maltose in feces indicates that maltose production occurred, but further degradation did not occur, indicating that the inhibition of α-glucosidase, mainly DNJ-1, by MLP was stronger than the inhibition of α-amylase activity. This result is consistent with previous findings showing that 1-DNJ also has inhibitory activity against α-amylase, but is less potent than its inhibitory activity against α-glycosidase [ 42 , 43 , 44 ]. Furthermore, it is likely that maltose, which may have been produced in the upper gastrointestinal tract and small intestine, was not efficiently degraded or utilized by bacteria in the colon and was excreted in the feces.…”

Inhibition of α-glucosidase activity by Morus australis fruit food

“…The glucose concentration in the M. australis dried fruit was 123-262 mg/g [13]. We also reported that 1-DNJ and glucose are the components in M. australis fruit, that are involved in the inhibition of maltase, glucoamylase, sucrase, and isomaltase [13].…”

“…We previously reported that the 1-DNJ concentration in the M. australis dried fruit were 0.04-0.29 mg/g, which was considerably smaller than that in the M. australis leaf (4.0 mg/g) [11,13]. The glucose concentration in the M. australis dried fruit was 123-262 mg/g [13]. We also reported that 1-DNJ and glucose are the components in M. australis fruit, that are involved in the inhibition of maltase, glucoamylase, sucrase, and isomaltase [13].…”

“…However, little has been known about the inhibition of α-glucosidase by compounds contained in mulberry fruit. We previously reported that the 1-DNJ concentration in the M. australis dried fruit were 0.04-0.29 mg/g, which was considerably smaller than that in the M. australis leaf (4.0 mg/g) [11,13]. The glucose concentration in the M. australis dried fruit was 123-262 mg/g [13].…”

“…The glucose concentration of wine was 0 mg/mL while those of juice, vinegar drink, vinegar, and jam were 13.9-39.7 mg/mL. We previously reported the glucose concentrations of the M. australis fruits were 123-262 mg/g [13].…”