In-vitro α-amylase inhibitor activity-phytate relationships in proteins from Phaseolus beans

Abstract

Citric acid extracted, crystalline proteins and alkali extracted non-crystalline proteins from four types of Phaseolus beans were investigated for α-amylase inhibitory activity. The influence of phytate on the α-amylase inhibitory activity was also studied. The inhibitory activities of the non-crystalline proteins were higher than those of crystalline proteins. All proteins showed α-amylase inhibitory activity and contained phytate which correlated statistically ( r = 0·68, p ≤ 0·01) with the α-amylase inhibitory activity. Free phytate did not inhibit α-amylase activity; however, phytate in combination with protein was inhibitory. The observed α-amylase inhibition of the bean proteins could be due to the presence of proteinaceous α-amylase inhibitor and/or a phytate protein complex with high inhibitory activity.