Shaddock peels (Citrus maxima) phenolic extracts inhibit α-amylase, α-glucosidase and angiotensin I-converting enzyme activities: a nutraceutical approach to diabetes management

Abstract

In this study, the interactions of free and bound phenolic-rich extracts from shaddock peels (popular in folklore for the management of diabetes and hypertension) with α-amylase and α-glucosidase (key enzymes linked to type-2 diabetes) and angiotensin I-converting enzyme (ACE) (key enzyme linked to hypertension) were assessed. The free phenolics of shaddock (Citrus maxima) peels were extracted with 80% acetone, while the bound phenolics were extracted from the alkaline and acid hydrolyzed residue with ethyl acetate; and their interaction with the enzymes were assessed. The phenolic extracts inhibited α-amylase, α-glucosidase and ACE enzyme activities in a dose-dependent manner; however, bound phenolics had significantly higher (P<0.05) α-amylase inhibitory activities, than free phenolics, which had significantly higher (P<0.05) ACE inhibitory activities. There was no significant difference (P>0.05) in their α-glucosidase inhibitory activities. The stronger inhibition of α-glucosidase when compared to α-amylase is of great pharmaceutical importance. The phenolic inhibited sodium nitroprusside induced lipid peroxidation in pancreas in a dose dependent manner. Therefore, free and bound phenolic extracts from shaddock peels could be used as nutraceutical for the management of hypertension and type-2 diabetes.