Modifications of the chemical structure of phenolics differentially affect physiological activities in pulvinar cells of Mimosa pudica L. I. Multimode effect on early membrane events

• Benzoic acid-related phenolics inhibit the pulvinar reaction.
• The membrane potential modification directs the further physiological changes.
• Salicylic acid and aspirin show atypical effect on the physiological processes.
• Position of OH(s) on the aromatic ring impacts drastically biological activity.
• Halogen atom on the aromatic ring always increases the biological activity.

A study of the structure–activity relationship carried out on several benzoic acid-related phenolics indicates that this type of compounds hinders the osmocontractile reaction of pulvinar cells in the range of 0–100%. Tentatively, we tried to find a way that could explain this differential action. With this aim, the relationship between the inhibitory effect and important molecular physico-chemical parameters (namely lipophilicity and degree of dissociation) was drawn. In addition, the effect of a variety of these compounds was investigated on their capacity to modify the electrical transmembrane potential and induce modifications in proton fluxes. Finally, using plasma membrane vesicles purified from pulvinar tissues, we examined the effects of some selected compounds on the proton pump activity and catalytic activity of the plasma membrane H+-ATPase. Taken together, the results indicate that a modification of the molecular structure of phenolics may induce important variation in the activity of the compound on these early membrane events. Among the tested phenolics, salicylic acid (SA) and acetylsalicylic acid (ASA, aspirin) are of particuler note, as they showed atypical effects on the physiological processes studied.