STUDY OF ALUMINUM GALLIC ACID AND ALUMINUM GALLIC ACID METHYL-ESTER POTENTIOMETRICALLY USING COMPUTER-PROGRAM BEST

Potentiometric studies on complexation reaction between Al3+ (which ha s recently been implicated in neurological dysfunctions including Alzh eimer's disease) and 3,4,5-Trihydroxybenzoic acid (gallic acid) and it s methyl ester has been investigated. A computer program BEST was use to analyse the data. It is found that gallic acid form 1:1 complex up to pH 8.5 and a 1:2 complex between pH 8.5 and 11.0. Log beta1 and log beta2 values are 18.76 and 29.52, which are higher than those of Fe3 complex of the same ligand. The methyl ester of gallic acid forms 1:1 , 1:2 as well as 1.3 complexes with log beta1 log beta2 and log beta3 values of 23.8, 33.83 and 39.63 respectively. Implications of these fo rmation constants for polyphenol complexes of Al3+ upon Al absorption and resulting toxicity are discussed.