Synthesis of 3-O-methylgallic acid a powerful antioxidant by electrochemical conversion of syringic acid.

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". CONCLUSION: 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 GENERAL SIGNIFICANCE: 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.

Chemical composition and direct electrochemical oxidation of table olive processing wastewater using high oxidation power anodes.

Table olive processing wastewater (TOW) is a notoriously polluting due to its high organic and phenol content. To reduce them, an electrochemical process has been studied for the treatment of this effluent. Experiments were performed with a cell equipped with lead dioxide (PbO2) or boron-doped diamond (BDD) as anode and platinum as cathode, where Table Olive Wastewater (TOW) were destroyed by hydroxyl radicals formed at the anode surface from water oxidation. The comparative study of both systems shows the performance of the BDD anode compared to PbO2, explained by the large amounts of hydroxyl radicals generated effective at BDD anode and its synthesis characteristics. Using LC/MS analysis, it was possible to determine hydroxytyrosol, as major phenolic compounds, in table olive processing wastewater and its concentration reach 890 mg L-1. A possible reaction mechanism oxidation for hydroxytyrosol was proposed. The kinetics decays for hydroxytyrosol degradation on PbO2 anode follows a pseudo-first order reaction with a rate constant 0.9 h-1 for japp value 20 mA cm-2.

Comparative Study of Oil Quality and Aroma Profiles from Tunisian Olive Cultivars Growing in Saharian Oasis Using Chemometric Analysis.

Aroma profile, oxidative stability and quality parameters of virgin olive oil from four cultivars (Chemlali, Chetoui, Koroneiki and Rjim), grown in Rjim Maatoug oasis in southern of Tunisia, were studied for the first time. The olive oil samples were obtained during maturation from a crop season (2012-2013). The results showed the quality parameters, i.e., free fatty acid, UV absorbance at 232 and 270 nm, increases during maturation exceeding the upper limit established by the IOOC norm. Chlorophyll and carotenoid pigments tended to decrease during ripening stages. The trend of oxidative stability, total phenols and Odiphenols exhibited a reduction of antioxidant activity at more advanced stages of maturity. The marks achieved showed that oil quality degradation is due to the great drought of climate: high temperature, high light intensity and low rainfall. Studied aroma profiles of cultivars were also influenced by severe climatic conditions. Twenty-four compounds were characterized, representing 94.8-99.8% of the total volatiles. In all samples, a strong decrease was observed in aldehydes compounds.

Application of electrochemical technology for removing petroleum hydrocarbons from produced water using lead dioxide and boron-doped diamond electrodes.

Although diverse methods exist for treating polluted water, the most promising and innovating technology is the electrochemical remediation process. This paper presents the anodic oxidation of real produced water (PW), generated by the petroleum exploration of the Petrobras plant-Tunisia. Experiments were conducted at different current densities (30, 50 and 100 mA cm(-2)) using the lead dioxide supported on tantalum (Ta/PbO2) and boron-doped diamond (BDD) anodes in an electrolytic batch cell. The electrolytic process was monitored by the chemical oxygen demand (COD) and the residual total petroleum hydrocarbon [TPH] in order to know the feasibility of electrochemical treatment. The characterization and quantification of petroleum wastewater components were performed by gas chromatography mass spectrometry. The COD removal was approximately 85% and 96% using PbO2 and BDD reached after 11 and 7h, respectively. Compared with PbO2, the BDD anode showed a better performance to remove petroleum hydrocarbons compounds from produced water. It provided a higher oxidation rate and it consumed lower energy. However, the energy consumption and process time make useless anodic oxidation for the complete elimination of pollutants from PW. Cytotoxicity has shown that electrochemical oxidation using BDD could be efficiently used to reduce more than 90% of hydrocarbons compounds. All results suggest that electrochemical oxidation could be an effective approach to treat highly concentrated organic pollutants present in the industrial petrochemical wastewater and significantly reduce the cost and time of treatment.