Soybean phenolic-rich extracts inhibit key-enzymes linked to type 2 diabetes (α-amylase and α-glucosidase) and hypertension (angiotensin I converting enzyme) in vitro

This study sought to assess the inhibitory activities of phenolic-rich extracts from soybean on cc-amylase, a-glucosidase and angiotensin I converting enzyme (ACE) activities in vitro. The free phenolic extract of the soybean was obtained by extraction with 80% acetone, while that of the bound phenolic extract was done by extracting the alkaline and acid hydrolyzed residue with ethyl acetate. The inhibitory action of these extracts on the enzymes activity as well as their antioxidant properties was assessed. Both phenolic-rich extracts inhibited alpha-amylase, alpha-glucosidase and ACE enzyme activities in a dose dependent pattern. However, the bound phenolic extract exhibited significantly (P < 0.05) higher alpha-amylase and ACE inhibition while the free phenolic extract had significantly (P < 0.05) higher alpha-glucosidase inhibitory activity. Nevertheless, the free phenolic extract had higher alpha-glucosidase inhibitory activity when compared to that of alpha-amylase; this property confer an advantage on soybean phenolic-rich extracts over commercial antidiabetic drugs with little or no side effect. And inhibition of ACE suggests the antihypertension potential of soybean phenolic-rich extracts. Furthermore, the enzyme inhibitory activities of the phenolic-rich extracts were not associated with their phenolic content. Therefore, phenolic-rich extracts of soybean could inhibit key-enzyme linked to type 2 diabetes (alpha-amylase and alpha-glucosidase) and hypertension (ACE) and thus could explain in part the mechanism by which soybean renders these health promoting effect. (C) 2011 Elsevier GmbH. All rights reserved.