Determination of antioxidant activities and amylase inhibitory of the bioactive compounds extracted from colored beans using solvent extraction method

Abstract

The colored bean extracts had revealed the inhibitory potential against two carbohydrate digestive enzymes: alpha-glucosidase and alpha-amylase. The meal extract showed the presence of phenolic and flavonoids which possessed high antioxidant activities. The two solvents (ethanol, methanol) with the ratio of solvent to water at 75:25 were used to determine the best solution for extraction of the high amount of total phenolic compounds (TPC) in the colored beans. The Folin-Ciocalteu’s method was used to determine TPC and the DPPH scavenging was used to determine antioxidants in the extracts. Total phenolic content in black beans was 314.7 µg FAE\g flour in methanol and 240.3 µg FAE\g flour in ethanol, respectively. The values of total phenolic content from red bean, green bean and white bean were also higher in methanol than in ethanol extract. The black beans extracted in 75% methanol had the highest content of antioxidant capacity (87.4%), followed by red bean (84.1%), green bean (20.2%) and white bean (17.4%). Black bean possessed the best antioxidant activity in most cases, and showed the strongest inhibitory potential against alpha-amylase (78% in methanol solvents) and alpha-glucosidase (51.9% in ethanol solvents) as well. As a result, the extracts of colored beans may have potential applications in the food industry for production of functional food for diabetic patients.

Keywords: colored beans, alpha-glucosidase inhibitory, alpha-amylase inhibitory, antioxidants, DPPH scavenging