Adesegun J Kasimawo¹, Bilqis A Lawal², Ini Ekpe³, Utuekong E Ekong⁴, Aniefiok Udobre⁴, Augustine A Ahmadu⁵

Abstract

Purpose: To investigate the antioxidant and in vitro antidiabetic activities of the n-butanol fraction and isolated compounds from the stem bark of Acacia auriculiformis. Methods: Vacuum liquid chromatography (VLC) was performed on the n-butanol fraction using a gradient elution technique. Fractions 6 and 7 eluted with 5% methanol in dichloromethane afforded compound 1, while fractions 12 and 13 eluted with dichloromethane: methanol (80:20) were pooled together and purified over Sephadex LH-20 to afford compound 2. The chemical structures of the purified compounds were established using 1H- and 13C-NMR and mass spectrometry. Antioxidant activity of the n-butanol fraction and isolated compounds was evaluated using 2,2-diphenyl-1 picrylhydrazyl (DPPH), 2,2′-azinobis (3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS) and nitric oxide (NO) scavenging assays, while in vitro antidiabetic activity was evaluated using α-amylase and α glucosidase enzymes. Results: Compounds 1 and 2 were identified as ethyl gallate and catechin on the basis of NMR and MS and compared with existing literature in the field. Catechin showed strong antioxidant activity in DPPH and ABTS assays with IC50 of 46.74 and 17.15 µg/mL versus ascorbic acid, with IC50 of 73.87 and 27.28 µg/mL, respectively, but weak nitric oxide scavenging activity with an IC50 of 208.87 µg/mL compared to 99.65 µg/mL for ascorbic acid. The in vitro antidiabetic assay revealed that catechin had weak inhibition against α-amylase (IC50 = 545.48 µg/mL) and moderate inhibition against α-glucosidase (IC50 = 201.32 µg/mL) compared to acarbose. Conclusion: This study has revealed the potential of catechin as a strong antioxidant against DPPH and ABTS radicals with moderate α-glucosidase inhibitory activity.