Inhibition of Digestive Enzymes, Antioxidant and Free Radical Scavenging Capacities of Stem Bark Extracts of Coula edulis Baill (Olacaceae)

Prolonged hyperglycemia enhances oxidative stress. Bioactive compounds extracted possess antioxidant, anti-free radical potentials or the ability to reduce blood sugar levels. The objective of this study was to evaluate the antioxidant properties of extracts of stem bark of Coula edulis Baill., their abilities to trap free radicals and glucose, as well as their ability to inhibit α-amylase and invertase activities. In vitro assays were used to test the trapping capacity of extracts on DPPH, ABTS, NO, and OH radicals; to evaluate the antioxidant capacity, the activity of glycosylation and the capacity of inhibition of the activities of α-amylase and invertase were conducted. Also, phenolic, flavonoid and alkaloid contents of extracts were determined. Results showed that extracts of the stem bark of C. edulis have anti-radical properties. The extracts chelate DPPH, hydroxyl (OH), nitrite oxide (NO), ABTS radicals, and even glucose. The IC50 values varied depending on the nature of the extraction solvent. Ethanolic extract has the highest polyphenolic content (289.12 ± 30.31 µg catechin equivalent/g), flavonoids (1.12 ± 0.09 µg quercetin equivalent/g) and alkaloids (5.54 ± 0.59 µg quinin equivalent/g). The extracts also reduce invertase and α-amylase activities. C. edulis extracts present strong antioxidant potentials and can be used as a source of natural antioxidants for the prevention of oxidative stress and hyperglycemia.