Effect of processing methods on the antioxidant properties and inhibition of α-amylase and α-glucosidase by African pear (Dacryodes edulis) fruit

Abstract

This study sought to investigate the effect of two traditional processing methods (roasting and hotwater treatment) of African pear (Dacryodes edulis [G. Don] H.J. Lam. [Burseraceae]) on the phenolic content, antioxidant properties and inhibition of two carbohydrate hydrolysing enzymes relevant to type 2 diabetes management (α-glucosidase and α-amylase). Some African pear samples were roasted for 5 min, while some were treated in hot water for 5 min. Thereafter, the total phenolic and flavonoid content, antioxidant activities, and interaction of the raw and processed samples with α-amylase and α-glucosidase were determined. The results of the total phenol and flavonoid contents of the raw, hot-water-treated and roasted African pear samples revealed that the roasted samples had significantly (p<0.05) higher total phenol (22.4 mg/g) and flavonoid (3.14 mg/g) content than hot-water-treated (total phenol [16.2 mg/g], total flavonoid [2.32 mg/g]) and raw samples (total phenol [12.1 mg/g], total flavonoid [1.91 mg/g]). The roasted samples had the highest radical-scavenging and Fe2+-chelating abilities, as well as inhibition of Fe2+-induced lipid peroxidation in rat pancreas in vitro; the raw samples had the least. Similarly, the samples inhibited both α-amylase and α-glucosidase activities in a dose-dependent manner; however, the processed samples had significantly higher inhibition of α-amylase and α-glucosidase activities than the raw samples. The higher phenolic content, antioxidant properties and inhibition of key enzymes (α- amylase and α-glucosidase) linked with type 2 diabetes in the roasted samples show that this is a better processing method for African pear than hot-water treatment.