title: Synthesis of 3-O-methylgallic acid a powerful antioxidant by electrochemical conversion of syringic acid.
abstract: BACKGROUND
  A kinetic study of the electrochemical oxidation of syringic acid (3,5-dimethoxy-4-hydroxybenzoic acid) by cyclic voltammetry at treated gold disk was combined with results of electrolyses at Ta/PbO2 anode in order to convert it into potentially high-added-value product.
  
  
  METHODS
  The electrochemical oxidation of syringic acid was carried out in order to convert this compound to 3-O-methylgallic acid. This latter was identified by mass spectrophotometry using LC-MS/MS apparatus. The 3-O-methylgallic acid synthesis was controlled by cyclic volammetry, Ortho-diphenolicdeterminations and DPPH radical-scavenging activity.
  
  
  RESULTS
  The proposed mechanism is based on the hypothesis of a bielectronic discharge of syringic acid molecule under free and adsorbed form involving two intermediate cation mesomers. Hydrolysis of the more stable of this last one leads to the formation of the 3,4-dihydroxy-5-methoxybenzoic acid (3-O-methylgallic acid) as a major product. The latter aromatic compound was synthesized by anodic oxidation of syringic acid at PbO2 electrode. The cyclic voltammogram of the electrolysis bath of syringic acid shows that the anodic peak potential of 3-O-methylgallic acid was lower (Epa=128mV) than that of SA (Epa=320mV). And the strongest antiradical activity was detected when the 3-O-methylgallic acid concentration was higher".
  
  
  CONCLUSIONS
  The electrochemical oxidation using PbO2 anode is a rapid, simple and efficient method tool for a conversion of SA into 3-O-methylgallic acid, a potent antioxidant derivative
  
  
  CONCLUSIONS
  The electrochemical process consists in a simple transformation of the syringic acid into 3-O-methylgallic acid having a better antioxidant capacity. This result has been justified by cyclic voltametry which shows that anodic peak of 3-O-methylgallic acid is reversible. Furthermore, its potential is lower than that of the irreversible anodic peak of syringic acid to 3-O-methylgallic acid.
authors: Laboratoire d'Electrochimie et Environnement, Université de Sfax, Tunisia.
authors: Olfa Dridi
authors: OD
authors: Gargouri
authors: Boutheina
authors: B
authors: Gargouri
authors: Souhel Kallel
authors: SK
authors: Trabelsi
authors: Mohamed
authors: M
authors: Bouaziz
authors: Ridha
authors: R
authors: Abdelhédi
mesh_terms: D000975:Antioxidants / Q000138:chemical synthesis* / Q000737:chemistry*; D004572:Electrolysis / Q000379:methods*; D005707:Gallic Acid / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D006046:Gold / Q000737:chemistry; D007854:Lead / Q000737:chemistry; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry; D013635:Tantalum / Q000737:chemistry
chemical_list: D000975:Antioxidants; D010087:Oxides; D007854:Lead; C047365:lead oxide; D005707:Gallic Acid; D013635:Tantalum; D006046:Gold; C025525:3-O-methylgallic acid; C001945:syringic acid