In Vitro α-Amylase and α-Glucosidase Inhibitory and Antioxidant Activities of the Crude Extract and Solvent Fractions of Hagenia abyssinica Leaves

Background. The leaves of Hagenia abyssinica have been used in the management of diabetes mellitus in Ethiopian folk medicine. Thus, this study is aimed at investigating the in vitro alpha-amylase and alpha-glucosidase inhibitory and antioxidant activities of the crude extract and solvent fractions of H. abyssinica leaves. Methods. The in vitro alpha-amylase and alpha-glucosidase inhibitory and antioxidant activities of the plant extract were assessed using 3,5-dinitrosalicylic acid (DNSA), p-nitro-phenyl-a-D glucopyranoside (p-NPG), and 1,1-diphenyl-2-picrylhydrazyl (DPPH) assays, respectively. Each value of percent inhibition of alpha-amylase, alpha-glucosidase, and DPPH scavenging effect was presented as means +/- SEM (n=3). Results. The alpha-amylase inhibitory activity of the crude extract and solvent fractions was found to be concentration-dependent. The strongest activity was exhibited by the crude extract at the highest concentration with a percentage inhibition of 74.52% (IC50, 14.52 mu g/ml) followed by water fraction 68.24% (IC50, 16.31 mu g/ml), ethyl acetate fraction 61.57% (IC50, 18.73 mu g/ml), and chloroform fraction 56.87% (IC50, 21.57 mu g/ml) of H. abyssinica leaves. In the alpha-glucosidase inhibition assay, the maximum activity was exhibited by the aqueous fraction 62.54% (IC50, 11.67 mu g/ml) followed by ethyl acetate fraction 54.97% (IC50, 15.89 mu g/ml), crude extract 46.79% (IC50, >16.5 mu g/ml), and chloroform fraction 36.44% (IC50, >16.5 mu g/ml). In the antioxidant assay, the crude extract exhibited the highest antioxidant activity 86.36% (IC50, 10.25 mu g/ml) followed by water fraction 78.59% (IC50, 13.86 mu g/ml), ethyl acetate fraction 71.58% (IC50, 16.34 mu g/ml), and chloroform fraction 63.65% (IC50, 18.83 mu g/ml). Conclusion. This study has revealed that H. abyssinica leaves possess noticeable in vitro alpha-amylase and alpha-glucosidase inhibitory and antioxidant activities.