Evaluation of α-Amylase and α-Glucosidase Inhibitory Activity of Flavonoids

Ken Ng

doi:10.15436/2377-0619.15.042

Abstract

A number of phenolic acids and flavonoids were screened for inhibitory activity against rat intestinal α-glucosidase and porcine pancreatic α-amylase. The phenolic acids were not inhibitory to both enzymes at 1 mM. Inhibition of α-amylase by flavonoids mirrored the inhibition of α-glucosidase in that both baicalein and myricetin inhibited the enzyme most strongly, but differs in that spectrum of flavonoid inhibition for α-amylase only restricted to these two flavonoids while it was more wide spread for the inhibition of α-glucosidase. Baicalein inhibited α-amylase and α-glucosidase activity by 41.1±2.6% and 56.9±1.7% at 1 mM, respectively. Myricetin inhibited α-amylase and α-glucosidase activity by 35.9±3.8% and 47.7±2.4% at 1 mM, respectively. The IC50 (concentration required for 50% reduction activity) of baicalein (0.713±0.034 mM) and myricetin (1.030±0.026 mM) confirmed that baicalein is the most potent flavonoid inhibitor against α-glucosidase in the flavonoid series studied.

Highlights

Controlling postprandial hyperglycaemia at the early pre-diabetes stage is an important preventative strategy against developing full blown diabetes mellitus and in glycemic control for diabetics (DM)[1]
Inhibition of rat intestinal α-glucosidase by flavonoids Figure 1 shows the structures of the flavonoids studied, which are flavones, isoflavones, flavonols, flavanones, and flavanols ((±)-catechin, (-)-epigallocatechin, (-)-epigallocatechin gallate)
In order to get a better evaluation of the potency of the inhibitory flavonoids, the IC50, which is the concentration of inhibitor required for 50% reduction in activity, were determined (Table 1)

Summary

Introduction

Controlling postprandial hyperglycaemia at the early pre-diabetes stage is an important preventative strategy against developing full blown diabetes mellitus and in glycemic control for diabetics (DM)[1]. In this paper we compare the inhibition of mammalian α-amylase and α-glucosidase by different classes of flavonoids so as to get a better understanding of their contribution to inhibitory activities in plant foods or herbs. Inhibition of rat intestinal α-glucosidase by flavonoids Figure 1 shows the structures of the flavonoids studied, which are flavones (flavone, 5-hydroxyflavone, 6-hydroxy-flavone, 7-hydroxyflavone, chrysin, baicalein, baicalin, oroxylin A), isoflavones (genistein, daidzein), flavonols (galangan, kaempferol, quercetin, myricetin), flavanones (pinocembrin, naringenin), and flavanols ((±)-catechin, (-)-epigallocatechin, (-)-epigallocatechin gallate).

Results

Conclusion