Inhibitory effects of Anadenanthera colubrina (Vell.) Brenan stem bark extract on -glucosidase activity and oxidative stress

In this study, we investigated the promising potential of Anadenanthera colubrina bark extract (BEAc) as a product to combat diabetes mellitus (DM). We evaluated the inhibitory effects of BEAc on α-glucosidase and the oxidation of biomolecules, as well as its main phytoconstituents. In terms of free radical scavenging, BEAc exhibited a dose-effect relationship. BEAc was more efficient than rutin and butylated hydroxytoluene and similar to ascorbic acid at the same concentrations. Evaluation of the IC50 confirmed the good activity of BEAc compared to positive controls and statistically determined to be equal to ascorbic acid. In in vitro α-glucosidase inhibition studies, BEAc generated 31 times more potent inhibition than acarbose and was dose-dependent at the concentrations tested. Lineweaver-Burk and Michaelis-Menten plots obtained for kinetic analysis showed that BEAc competitively inhibited the α-glucosidase catalyzed reaction. Chemical analysis of BEAc by HPLC revealed that the plant is rich in phenolic compounds and confirmed its capacity to inhibit α-glucosidase. Fourteen compounds were identified by reference to authentic standards: Gallic acid, catechin, syringic acid, chlorogenic acid, p-coumaric acid, naringin, vitexin, rutin, isorhamnetin, hesperidin, myricetin, morin, rosmarinic acid, and quercetin. Thus, this study provides the first evidence of the antidiabetic activity of A. colubrina bark and determines its possible modes of action on carbohydrate metabolism via inhibition of α-glucosidase and the control of biomolecule oxidation. These data support the potential use of this plant for the development of promising multi-target therapy products combining postprandial hyperglycemia control and biomolecule oxidation control. Key words: Kinetic analysis, phenolic content, diabetes mellitus, oxidation of biomolecules.