South Asian Research Journal of Natural Products

Acacia sieberiana is traditionally used for medicinal purposes, but information regarding the α-glucosidase inhibitory activity of its stem bark extract remains limited. This study investigated the in vitro α-glucosidase inhibitory activity of the dichloromethane:ethylacetate (1:1)-soluble fraction of A. sieberiana stem-bark methanol extract and partially characterized a compound isolated from the extract. Extraction of the dried stem bark was carried out using a maceration technique with methanol, and α-glucosidase inhibition was evaluated using p-nitrophenyl-α-D-glucopyranoside as the substrate. The dichloromethane:ethylacetate (1:1)-soluble portion of the extract was further subjected to column chromatography, and the resulting isolate coded SBU was analyzed using Fourier-transform infrared spectroscopy and gas chromatography–mass spectrometry. The extract produced concentration-dependent inhibition of α-glucosidase activity, with an IC₉₀ of 833.38 mg/mL. Metformin (known α-glucosidase inhibitor) produced an IC₅₀ of 1.04 mg/mL and IC₉₀ of approximately 2.00 mg/mL. FTIR analysis of the isolate showed the presence of hydroxyl/carbonyl, unsaturation, aliphatic, and C–O containing functional groups. GC–MS analysis of the isolate revealed a molecular ion at m/z 281Da, and a library comparison suggested the compound 9-(Z)-octadecenamide (oleamide), with molecular formula C₁₈H₃₅NO. These findings demonstrate the α-glucosidase activity inhibitory effect of A. sieberiana extract and indicate the presence of bioactive constituents in the extract.