Evaluation of α-glucosidase inhibitory activity in colored foods: A trial using slope factors of regression curves

Abstract

Functional foods which have α-glucosidase inhibitory activity are effective in controlling blood sugar levels in persons with a risk of diabetes. We have developed a simple method for screening of functional foods which is useful for colored samples. In this method, we use the slope of the liner regression curve of the absorbance of product in a 96-well microplate as an index of activity. This was applied to the measurement of α-glucosidase inhibitory activity in beverages such as tea. Mulberry leaf tea had the highest inhibitory activity and Guava tea had the second highest activity of all samples used in this experiment. Green teas showed little α-glucosidase inhibitory activity, and coffee had no activity. In order to confirm the effectiveness of this method, we undertook addition and recovery of 1-Deoxynojirimycin in a coffee sample. The regression curve obtained showed good linearity. This method seems to be useful and convenient for measurement of α-glucosidase inhibitory activity in colored beverages.