Abstract: The purpose of this investigation was to evaluate the in vitro bioactivity of buckwheat hull extract (BHE). BHE was purified and separated into 5 fractions: BHE-M1, BHE-M2, BHE-M3, BHE-M4 and BHE-M5 by sequential chromatography on macroporous resins. The inhibitory activity against α-glycosidase and advanced glycosylation end products (AGEs) formation of these fractions was assessed. The results indicated that the purity of BHE was increased from 30.8 to 65.3 g/100 g after purification and BHE-M4 had the highest purity of 89.2 g/100 g among the five fractions. The percentage inhibition of α-glycosidase by BHE, purified BHE, BHE-M2, BHE-M3, BHE-M4 and BHE-M5 at a concentration of 1.000 mg/mL were 16.03%, 24.39%, 18.04%, 25.46%, 28.23% and 26.24%, respectively, which were significantly higher than that of the positive control arabinose. In glucose-bovine serum albumin (G-BSA) and fructose-bovine serum albumin (F-BSA) systems, all samples except BHE-M1 had a stronger inhibitory effect on AGEs formation than amino guanidine with BHE-M4 being the mwost effective. High performonce liquid chromatography-mass spectrometry (HPLC-MS) results indicated that flavonoids identified in BHE-M4 were kaempferol-3-O-β-D-glucoside or kaempferol-3-O-β-D-galactosidase, vitexin, rutin, isoquercitrin or hyperoside and quercitrin. Conclusively, flavonoid-rich extracts from buckwheat hull possessed a stronger inhibitory effect on α-glycosidase activity and AGEs formation, implying that flavonoids are the major antidiabetic components in buckwheat hull.

Key words: buckwheat hull, flavonoids, macroporous resin, diabetes mellitus, α-glycosidase, advanced glycosylation end products (AGEs)