2.8.3. Inhibition assay for a-amylase activity
a-Amylase inhibitory activity was assayed according to the procedure
described by Wang, Du, and Song (2010) with a slight modification.
Amylase activity was determined using soluble starch
(1%) as a substrate in 0.05 M sodium phosphate buffer (pH 6.8)
containing 1 mM CaCl2. Briefly, 400 ll of a-amylase solution
(20 U/ml) was mixed with 1.0 ml of sodium phosphate buffer
(pH 6.8) and 200 ll of the TFs in 75% aqueous ethanol (8–64 mg/
ml). After incubation at 37 C for 10 min, 300 ll of the starch solution
(1%) was added and the mixture re-incubated at 37 C for
20 min. The reaction was terminated by adding 0.2 ml of dinitrosalicylic
acid solution and boiled for 10 min in a boiling water bath.
The total volume was made up to 8.0 ml with distilled water. The