Effects of Aqueous Extracts of Some Citrus Peels on key Enzymes Linked With Type-2 diabetes

Abstract

An approach to controlling blood glucose levels in individuals with type-2 diabetes is the inhibition of enzymes involved in the breakdown  of starch and absorption of glucose, such as α-amylase and α-glucosidase. This study therefore, sought to characterize the interaction of  aqueous extracts from some Nigerian citrus peels [orange (Citrus sinensis), grapefruit (Citrus paradisii) and shaddock (Citrus maxima)]  with α-amylase and α-glucosidase in vitro. The total phenolic, flavonoid, vitamin C content and antioxidant activities were also  determined. The results revealed that orange peels had the highest total phenol content (8.33mg/g) and flavonoid content (0.58mg/g) as  compared to grapefruit [total phenol (6.50mg/g), flavonoid (0.29mg/g)] and shaddock peels [total phenol (5.00mg/g), flavonoid  (0.15mg/g)]. Also, orange peels’ aqueous extracts showed the highest antioxidant potential as typified by a higher reducing power, ABTS  radical scavenging ability and inhibition of Fe²⁺ - and sodium nitroprusside- induced lipid peroxidation in rat’s pancreas – in vitro. The  aqueous extracts from the citrus peels inhibited α-glucosidase and α-amylase activities, though with a stronger inhibition of  α-glucosidase [orange (37.50%), grape (50.0%), shaddock (37.50%)] than α-amylase activities [orange (25.32%), grape (29.29%), shaddock  (21.34%)]. The phenolic contents, vitamin C contents, antioxidant activities and inhibition of key enzymes linked with type 2 diabetes  suggests the potential use in the control of blood glucose levels associated with type-2 diabetes.