Background: In this study, interaction of free and bound phenolic extracts from selected tropical underutilized legumes (a popular folklore for the management of diabetes and hypertension) with key enzymes linked to type 2 diabetes (α-glucosidase and α-amylase) and hypertension (angiotensin I converting enzyme, ACE) was assessed.
Methods: The free phenolic extracts of the soybean were obtained by extracting powdered legume seeds with 80% acetone, whereas the residue was subjected to alkaline and acid hydrolysis before extraction with ethyl acetate to obtain the bound extracts. Thereafter, enzyme (α-amylase, α-glucosidase, and ACE) inhibitory studies and antioxidant capacity of the extracts were investigated.
Results: The free and bound phenolic extracts inhibited α-amylase, α-glucosidase, and ACE activities in a dose-dependent manner. However, the free phenolic extracts of all the legumes were stronger inhibitors of α-glucosidase than their corresponding bound phenolic extracts. In addition, the free phenolic extracts (except melon) exhibited stronger ACE inhibition than their corresponding bound phenolic extracts. All the phenolic extracts significantly (p<0.05) inhibited Fe2+-induced oxidative stress in the pancreas (in vitro) and exhibited strong antioxidant activities.
Conclusions: The inhibition of the α-amylase, α-glucosidase, ACE, and oxidative stress by the phenolic extracts could be a part of the mechanism through which these underutilized legumes manage/prevent type 2 diabetes and hypertension. However, as revealed by this study, bambara groundnut with the best enzyme inhibitory potentials coupled with strong antioxidant properties ranked highest, whereas melon seed ranked least.