Screening and extraction process optimization for potential α-glucosidase inhibitors from quinoa seeds

To explore the potential factors of quinoa to control blood sugar, five active components, polyphenols, flavonoids, saponins, alkaloids and polysaccharides, were extracted from three kinds of quinoa by using ten different solvents, then in vitro α-glucosidase activity inhibitory experiment these 30 kinds of extracts were determined. Results showed that the total polyphenols from black quinoa had a strong correlation on the inhibition of α-glucosidase (r = 0.91, P < 0.001). Thus, the extraction process of black quinoa crude polyphenols (BQCP) was carried out, and the most efficient extraction conditions were: material-liquid ratio was 1:70 g/mL, ultrasonic temperature was 45 °C, ultrasound time was 30 min, ultrasonic power was 400 W, the optimal extraction amount was 5.148 ± 0.038 mg/g. Moreover, the black quinoa polyphenols (BQP), purified from BQCP, had stronger inhibitory ability on α-glucosidase (IC₅₀ = 0.59 mg/mL) and α-amylase (IC₅₀ = 2.85 mg/mL) and its inhibition effect was greatly to BQCP. This study demonstrates that BQP can be a good potential source of natural hypoglycemic drugs or functional foods.