Chemical profiling, <i>in vitro</i> antioxidant and antidiabetic assessment of flavonoids from the ethanol extract of <i>Hermannia geniculata</i> root

Abstract

Determination of the in vitro antioxidant and the inhibitory potential of flavonoids from Hermannia geniculata (FHG) roots on diabetes-linked enzymes was carried out. The chemical profiling of FHG roots extract was investigated using High Pressure Thin Layer Chromatography (HPTLC) fingerprint analysis. The reactive oxygen scavenging potential of the extract was analyzed. Starch solution (1%) was reacted with different concentrations of FHG extract to determine the α-amylase inhibitory potential of the extract while α- glucosidase inhibition assay was carried out through incubation of different concentrations of the extract followed by addition of p-ntrophenyl-α-Dglucopyranoside solution. HPTLC results indicated the presence of flavonoids/ phenolcarboxylic acid, and Kaemferol (Rf 0.80) were detected in the extract with retention factor Rf. ranging from 0.08 to 0.95. FHG extract showed commendable antioxidant properties with IC50 values (3.07± 0.12, 2.13± 0.67) µg/mL for 1, 1-diphenyl-2- picrylhydrazyl (DPPH) and 2, 2-azino-bis (3- ethylbenzothiazoline-6-sulphonic) acid (ABTS) radicals which were lower and significantly different (p<0.05) compared to standard silymarin with IC50: (3.55± 0.10, 2.77± 0.75) µg/mL for DPPH and ABTS respectively. The results indicated mild inhibition of α-amylase with IC50: (5.55± 0.37) µg/mL which was higher and significantly different (p<0.05) from acarbose with IC50: (3.81± 0.29) µg/mL. Moreover, the extract showed 73% inhibition of α-glucosidase. Kinetic studies of FHG extract revealed competitive and mixed non-competitive inhibition of α- amylase and α-glucosidase respectively. This study indicated FHG capabilities of scavenging reactive oxygen species and reducing hydrolysis of starch responsible for post-prandial hyperglyceamia seen in type 2 diabetes mellitus.

Keywords: Antidiabetic, Antioxidant, Flavonoids, Hermannia geniculate, HPTLC