Anticholinesterase activity of phenolic acids and their derivatives.

The ability of 36 phenolic acids and their derivatives to inhibit acetyl- and butyrylcholinesterase was studied. The most efficient acetylcholine inhibitors were: carnosic acid = gentisic acid > 3-hydroxy-4-methoxycinnamic acid = ethyl ferulate = ethyl vanillate = nordihydroguaiaretic acid > ethyl 4-hydroxybenzoate = methyl ferulate. The order of effectiveness towards butyrylcholinesterase was: carnosic acid > nordihydroguaiaretic acid = ethyl ferulate > salicylic acid > gentisic acid > rosmarinic acid = caftaric acid > homogentisic acid. The inhibitory activity was dependent on the number/position of OH or/and OCH3 groups attached to a phenol ring. It can be speculated that OCH3 substitution in the phenol ring can promote a higher antibutyrylcholinesterase activity (although not statistically confirmed at p < 0.05). The presence of a CH=CH-COOH group had a highly favourable effect on the antiacetylcholinesterase activity compared with a CH2-CH2-COOH or a COOH group. Methyl and ethyl esters were more potent inhibitors than the corresponding free acids. The molecular weight of the compounds (in the range of M = 154.12 - 474 g/mol) played a minor role in this context.