Alpha (α)-amylase Inhibitory Property of Anthocleista nobilis Leaf Extract

Aims: Alpha (α)-amylase inhibitors from plants are preferable for type 2 diabetes treatment because of their relative potency and safety. This study examined, in vitro, the inhibitory effect of Anthocleista nobilis leaf extract on starch hydrolysis catalyzed by α -amylase (extracted from moated sorghum).

Place and Duration of Study: Department of Biochemistry (School of Biological Sciences) and Department of Chemistry, School of Physical Sciences, University of Cape Coast, Ghana, between June 2021 and August 2021.

Methodology: Leaves of A. nobilis were air-dried, pulverized, and macerated in 70% aqueous ethanol for 72 hrs. The filtrate was concentrated and reconstituted in 0.02M Sodium phosphate buffer (pH 6.9) for further analysis including Phytoconstituents screening. In vitro analysis of α -amylase activity as well as inhibitory effect of A. nobilis extract on α -amylase was performed. The Lineweaver-Burk plot was employed in the inhibition analysis to determine the inhibition type, maximum initial reaction rate (Vmax), as well as the Michaelis constant (KM).

Results: The percentage inhibition of α-amylase ranged from 25.0 ± 0.46% - 85.7 ± 2.17% for 0.1mg/mL and 0.9mg/mL of the A. nobilis leaf extract respectively. The mode of α-amylase inhibition was found from the Lineweaver-Burk plot as mixed noncompetitive. The KM and Vmax were determined as 0.2043 mM and 0.1282 mM/min respectively. In contrast, KM for the control were 0.1537mM and Vmax of 0.09750 mM/min. The inhibition property of A. nobilis could be attributed to its phytochemicals such as flavonoids, saponins, alkaloids, tannins, and terpenoids that were present.

Conclusion: Anthocleista Nobilis leaf extract contains certain naturally occurring anti-diabetic compounds and could be explored for treating type 2 diabetic patients. These findings, however, need further work to validate the exact bioactive constituents responsible for the inhibitory effect.