In Vitro Anticholinesterase and Inhibitory Effects of the Aqueous Extract of Combretum molle (Combretaceae) Leaf on Rabbit Breathing

Purpose: In previous studies, the aqueous extract of Combretum molle was shown to inhibit disturbances of breathing induced by acetylcholine. The aim of this study was to elucidate themechanism of this inhibition. Methods: The aqueous extract of Combretum molle and an anti-asthmatic, salbutamol (reference), were tested at varying concentrations for their inhibitory effects on breathing. Acetylcholinesterase (AChE) was extracted from rabbit duodenum and its activity determined by Ellman’s assay using acethylthiocholine iodide (ACTH) as substrate. The rate of hydrolysis of acetylcholinesterase was spectrophotometrically monitored at 412 nm. Results: The results indicate that in the presence of C. molle extract, a considerable reduction in the variation of breathing amplitudes occurred. Furthermore, the extract probably contains anti-AChE substances. C. molle exerted non-competitive inhibition of acetylcholinesterase with Michaelis-Menten constant (KM) of 192 μM and velocity at maximal concentration of substrate (Vmax) of 4444 μM/min. Conclusion: These results support the use of C. molle leaf in the Pharmacopoeia of IvoryCoast as an anti-asthmatic, in view of its inhibitory effect on breathing disturbances.