View PDF Version
 
DOI: 10.1039/A809147A (Paper) Reference Section for: Phys. Chem. Chem. Phys., 1999, 1, 1915-1918

Pulse radiolysis studies on redox reactions of gallic acid: one electron oxidation of gallic acid by gallic acid–OH adduct

(Note: The full text of this document is currently only available in the PDF Version )

P Dwibedy, G R. Dey, D B. Naik, K Kishore and P N. Moorthy

Abstract

Using the pulse radiolysis technique, studies on reactions of 3,4,5-trihydroxybenzoic acid [gallic acid (GA)] with radical species generated in water are reported. At pH 6.8 and 9.7, OH radicals react with GA to give an adduct initially with rate constants of the order of 1×1010 d mol-1 s-1. This adduct then reacts with parent GA molecules with rate constants of the order 5×108 d mol-1 s-1 to give phenoxyl type radical species having absorption maxima in the 350 nm region. At pH 12 and 13.6, OH/O- radicals directly bring about oxidation of GA. Specific oxidants like azidyl radical bring about one electron oxidation at neutral and alkaline pHs with almost diffusion controlled rate constants. Rate constants for the reaction of Br2- radicals are found to be lower than those for OH radicals by an order of magnitude. At pH 0, both OH and Cl2- radicals react with GA to give phenoxyl type radicals. The phenoxyl radicals formed are quite stable at higher pHs, which make GA a good antioxidant. Rate constants for the reactions of eaq- with different protolytic forms of GA are determined.

References

  1. H. Schulz and G. Albroscheit, J. Chromatogr., 1988, 442, 353 CrossRef CAS.
  2. W. Brand-Willium, M. E. Cuvelier and C. Berset, Food Sci. Technol. (London), 1995, 28(1), 25–30 Search PubMed.
  3. H. Sakagami and K. Satoh, Anticancer Res., 1996, 16(3A), 1231 Search PubMed.
  4. M-E. Kuvelier, H. Rochard and C. Berset, Biosci. Biotech. Biochem., 1992, 56(2), 324.
  5. P. L. Teissedre, E. N. Frankel, A. L. Waterhouse, H. Peleg and J. B. German, J. Sci. Food Agric., 1996, 70(1), 55 CrossRef CAS.
  6. H. Iwahashi, H. Morishita, T. Ishii, R. Sugata and R. Kido, J. Biochem. (Tokyo), 1989, 105(3), 429 Search PubMed.
  7. S. P. Rosenberg, Corros. Australas, 1987, 12(1), 11 Search PubMed.
  8. B. Mueller and I. Foerster, Corrosion (Houston), 1996, 52(10), 786 Search PubMed.
  9. E. J. Land and E. Ebert, Trans. Faraday Soc., 1967, 63, 1181 RSC.
  10. S. V. Jovanovic, Y. Hara, S. Steenken and M. G. Simic, J. Amer. Chem. Soc., 1995, 117, 9881 CrossRef CAS.
  11. Z. Maskos, J. D. Rush and W. H. Koppenol, Free Radic. Biol. Med., 1990, 8, 153 CrossRef CAS.
  12. C. P. Moorehouse, B. Halliwell, M. Grrotweld and J. M. C. Gutteridge, Biochim. Biophys. Acta, 1985, 843, 261 CrossRef.
  13. M. A. Oturan, J. Pinson, D. Deprez and B. Terlein, New J. Chem., 1992, 16, 705 Search PubMed.
  14. J. T. Richards and F. A. Adams, Int. J. Food Sci. Technol., 1987, 22, 501 CAS.
  15. S. N. Guha, P. N. Moorthy, K. Kishore, D. B. Naik and K. N. Rao, Proc.-Indian Acad. Sci. (Chem. Sci.), 1987, 99, 261 Search PubMed.
  16. E. M. Fielden, in The Study of Fast Processes and Transient Species by Electron Pulse Radiolysis, ed. J. H. Baxendale and F. Busi, Riedel Publishing Co., Dordrecht, Holland, 1982, p. 49 Search PubMed.
  17. P. O'Neill and S. Steenken, Ber. Bunsen-Ges Phys. Chem., 1977, 81, 550 Search PubMed.
  18. H. S. Mahal, PhD Thesis, University of Mumbai, 1996.
  19. W. Bors, W. Heller, C. Michel and M. Saran, Methods Enzymol., 186, 343, Academic Press, New York, 1990 Search PubMed.