Natural extracts have been proved to be useful in different human pathological conditions. The scientific consideration of the therapeutic potential of plant extracts is still inappropriate due to the lack of both pharmacological and epidemiological basic studies. Here, we started from an electrophysiological point of view, a study on the effects of two extracts on the acetylcholine (ACh) release at the neuromuscular junction. The extracts purified from Sugar cane (policosanol) and Psidium guajava (quercetin) have been submitted to this study. The wide epidemiology of these agents suggests therapeutic potentials not yet well outlined at the basic level. Our data demonstrate some interactions in the modulation of the ACh release at the mouse neuro-muscular junction, which are well correlated with the suggested molecular mechanisms. Policosanol enhances to a small extent either the spontaneous or the evoked ACh release. Furthermore, an increase of the rate of the conformational change induced at the nicotinic receptor-channel complex by ACh is also observed. Quercetin induced a reduction of the ACh evoked release. The possibility that this effect could be ascribed to some interaction with presynaptic calcium channel is noteworthy. The results are discussed in terms of a possible interference with acetylcholinesterase by policosanol and of a presynaptic molecular action of quercetin modulating the cytosolic calcium concentration.
Copyright 1999 The Italian Pharmacological Society.