Glutinous rice ( Oryza sativa L.) protein extract with potent α-amylase inhibitory activity

This research screened for α-amylase inhibitory activity of twenties-five varieties Thai indigenous rice seeds. Based on specific inhibition, crude protein of var. Gai Ngaw (Gs. No. 13719) was selected for purification. The unbound proteins of the Q-Sepharose column named partially purified rice α-amylase inhibitor (RAI) revealed MW of approximately 14.4 kDa. The RAI was stable at pH 4 to 7 and heat stable up to 80 °C. The RAI had IC₅₀ of 15.92 ± 1.08 µg/ml. The double reciprocal plot implied a mixed-type inhibitor. The Dixon and Cornish-Bowden plots were used to estimate Ki and αKi. This suggested Thai indigenous rice seeds could potentially be developed as a food supplement for blood sugar and weight controls.

Keywords: Blood sugar lowering; Indigenous rice; Mixed-type inhibition; Weight control; α-amylase inhibitor protein.