Kinetics of acetylcholinesterase inhibitory activities by aqueous extracts of Acacia nilotica (L.) and Rhamnus prinoides (L'Hér.)

Abstract

Acetylcholinesterase (AChE) is a key target in the treatment of Alzheimer’s disease (AD). We studied the potential anti-AChE activities of Acacia nilotica(Leguminosae) and Rhamnus prinoides (Rhamnaceae) plants that have previously been shown to affect central nervous system activities. Sonicated aqueous extracts of A. nilotica and R. prinoides displayed significant AChE inhibition by about 56 and 53%, respectively, after 5 min incubation at 0.1mg/ml final assay concentration. Inhibition kinetics showed both plant preparations to be mixed inhibitors (specifically non-competitive uncompetitive type). Galanthamine was assayed as a positive control and was found to be a very potent mixed type (competitive non-competitive) inhibitor; IC50 of 0.0004 mg/ml compared to 0.079 mg/ml for A. nilotica and 0.201 mg/ml for R. prinoides. We conclude that although the AChE inhibition by A. nilotica and R. prinoides is not as potent as that of galanthamine, in addition to their known antioxidant and anti-inflammatory activities these plants could provide novel poly-pharmacological leads of potential benefit to the treatment of AD and therefore warrant further investigation. Key words: Alzheimer’s disease, acetylcholinesterase, enzyme inhibition, kinetics,Acacia nilotica, Rhamnus prinoides.