Inhibition of key enzymes linked to diabetes by Annona senegalensis Pers (Annonaceae) leaf in vitro

Abstract

Annona senegalensis Pers (Annonaceae) known as Wild Custard Apple is used locally in the treatment of diabetes in Nigeria. This study was aimed at investigating the inhibitory potential of A. senegalensis leaf extracts and fractions on the activities of some enzymes (α-amylase and α-glucosidase) linked to diabetes. Plant samples were extracted with n-hexane (HEX), ethyl cetate (EtOAc) and ethanol (EtOH) and the extracts were subjected to in vitro antidiabetic studies. The most active extract was further fractionated using column chromatography and the fractions obtained were screened for the inhibitory activities whilst the possible bioactive compounds were determined by Gas Chromatography Mass Spectroscopy (GC–MS). From the results, ethanolic extract possessed lowest IC50 values (α-amylase: 204.04 ± 6.38 μg/ml, α-glucosidase: 97.91 ± 2.40 μg/ml) compared to other extracts. The most active fraction (F-fraction) from the ethanolic extract showed lower IC50 values for α-amylase (237.14 ± 31.19 μg/ml) and α-glucosidase (88.25 ± 0.59 μg/ml). The data further showed that F-fraction is a competitive inhibitor (Vmax: 27.03 μmol/min, Km: 0.24%, ki value: 8.46 μg/ml) for α-amylase and non-competitive inhibitor for α-glucosidase (Vmax: 1.10 μmol/min, Km: 3.7 mmol/l, ki value: 1.26 μg/ml). Possible compounds revealed by GC–MS from F-fraction were hexadecanoic acid, methyl ester, 1,3-octadecenal, and 1,2-benzenedicarboxylic acid, and bis (2-methylpropyl) ester. Therefore, our present data showed that A. senegalensis showed inhibitory potentials on the activities of α-amylase and α-glucosidase, attributed to the possible presence of identified compounds.