Abstract:

The respective effects of buckwheat bran ethanol extract mainly composed of flavonoids and its high-pressure hydrolysate as well as the water extract from the material mainly composed of fagopyritols on α-glucosidase activity were measured using acarbose or D-chiro-inositol as a reference substance. The major components of the ethanol extract were flavonoids, with a total content of 74.0%, in which the relative content of rutin was 86.5% and those of quercetin and isoquercetin were at trace levels according to colorimetric and HPLC determinations. However, after high-pressure hydrolysis, the content of total flavonoids in the ethanol extract increased to 76.2%, of which rutin, quercetin and isoquercetin represented 60.6%, 25.2% and 13.5%, respectively. The major components of the water extract were 43.6% D-chiro-inositol and 2.9% inositol. All the three tested samples had inhibition effect onα-glucosidase in the following decreasing order: the hydrolysate of the ethanol extract ＞the ethanol extract ＞ the water extract. Their IC50 values were 0.0085, 0.0578 g/L and 17.3551 g/L, respectively. Therefore, highpressure hydrolysis could increase the inhibition effect of buckwheat bran ethanol extract onα-glucosidase activity (the IC50 of the hydrolysate was approximately one quarter of that of acarbose; the smaller IC50, the stronger inhibition effect). In addition, the water extract did not inhibit the activity of the enzyme at low concentrations, but had inhibition effect at high concentrations.

Key words: buckwheat extract, α-glucosidase, inhibitor, diabetes