INHIBITORY OF ?-AMYLASE AND ?-GLUCOSIDASE BY RAW, BOILED, AND ROASTED POTATOES

Man Kyu Huh* and In Sook Kye

ABSTRACT

This study was to evaluate and compare the α-amylase and α-glucosidase inhibitory activity of extracts from common brownish potato during two cooking methods. The α-amylase inhibitory activity of the raw potatoes was high, but not when boiled or toasted. α-amylase inhibitory activity of water extract for raw potato was evaluated 15.5% at 0.25 mg/ml and 38.4% at 1.0 mg/ml. The values of the boiled potato evaluated 16.3% at 1.0 mg/ml and that of the roasted potato evaluated 19.9%. There was no significant difference in the inhibitory activity of the two enzymes between boiled and roasted potatoes (p > 0.05). The half maximal inhibitory concentration (IC50) for α-amylase of raw potato was 170.8 ug/ml, whereas boiled potato was low, 209.7 ug/ml. α-glucosidase inhibition of water extract for raw potato evaluated at 0.25 mg/ml was 26.9% and that of 1.0 mg/ml was 51.5%. The values of α-glucosidase inhibition for boiled and roasted potatos evaluated at 1.0 mg/ml were 21.0% and 20.5%, respectively. The raw potatoes generally had slightly higher α-amylase and α-glucosidase inhibitory activity than boiled and roasted potatoes. Boiling and roasting treatments for potatoes showed reducing effects on the α-amylase and α-glucosidase inhibitory activity. The mode of inhibition of the raw potapo extracts against both α-amylase and α-glucosidase was confirmed by Lineweaver–Burk plots. Crude water extract competitively inhibited α-amylase and α-glucosidase.

Keywords: ?-amylase, ?-glucosidase, inhibitory activity, Lineweaver–Burk plots, potato.