Inhibitory effect of polyphenolic–rich extract from Cola nitida (Kolanut) seed on key enzyme linked to type 2 diabetes and Fe2+ induced lipid peroxidation in rat pancreas in vitro

Abstract

To investigate the inhibitory effect of phenolic-rich extracts from Cola nitida (C. nitida) seeds on key enzymes linked with type-2 diabetes and Fe(2+) induced oxidative stress in rat pancreas. The phenolic extract was prepared with 80% acetone (v/v). Subsequently, the antioxidant properties and inhibitory effect of the extract on α - amylase and α - glucosidase as well as on Fe(2+) induced lipid peroxidation in rat pancreas were determined in vitro. The result revealed that C. nitida extract inhibited α-amylase (EC50=0.34 mg/mL) and α-glucosidase (EC50=0.32 mg/mL) activities as well as Fe(2+) induced lipid peroxidation in rat pancreas in a dose dependent manner. In addition, the extract had high DPPH radical scavenging ability (EC50=2.2 mg/mL) and reducing power (8.2 mg AAE/g). Characterization of the main phenolic compounds of the extract using gas chromatography analysis revealed catechin (6.6 mg/100 g), epicatechin (3.6 mg/100 g), apigenin (5.1 mg/100 g) and naringenin (3.6 mg/100 g) were the main compounds in the extract. This antioxidant and enzyme inhibition could be some of the possible mechanism by which C. nitida is use in folklore for the management/treatment of type-2 diabetes. However, the enzyme inhibitory properties of the extract could be attributed to the presence of catechin, epicatechin, apigenin and naringenin.