S.C. Mordido,a M.J.F. Rebelo,a,b,*
a Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade de Lisboa (FCUL), b CECUL –FCUL, Campo Grande, C 8, 1749-016 Lisboa, Portugal
Abstract
The electrochemical behaviour of caffeic acid in acetate solutions with and without added ethanol was studied by cyclic voltammetry. Solutions of pH and ethanol content close to the wine values (3.5 and 12%, respectively) were studied as a first model approach, pursuing work previously done. Studies at pH 7.4 and different ionic strengths were also done.
It was found that cyclic voltammograms of caffeic acid acetate ethanolic solutions had oxidation peak potential values (≈ 470 mV) at pH 3.5 irrespective of the previous excursions of potential with the same set of electrodes. However, the cathodic peaks potentials and currents strongly depended on the cyclic voltammogram of the corresponding solvent electrolyte which had previously been run.
The separation of oxidation and reduction peak potentials evidenced the presence of dimmers of caffeic acid in solution, under the following conditions: 0.1 mol dm-3 acetate buffer pH 3.5 + 12% ethanol with the ionic strength increased by the addition of 0.05 mol dm-3 KCl; limits of the anodic potential: from –100 to + 700 mV and N2 bubbled through the solution for 10 minutes.
Keywords: caffeic acid, acetate buffer, ethanol, cyclic voltammetry.
]]>
Texto disponível em PDF
Full text only in PDF format
References
1. S. Chevion, M.A. Roberts, and M. Chevion,Free Rad. Biol. Med. 28(6) (2000) 860–870. [ Links ]
2. M. Nardini, M. D’Aquino, G. Tomassi, V. Gentili, M. Di Felice, C. Scaccini, Free Radic. Biol. Med. 19 (1995) 541–552.
3. J. Laranjinha, O. Vieira, V. Madeira, L. Almeida, Arch. Biochem. Biophys. 323 (1995) 373–381.
4. D. Galato, K. Ckless, M.F. Susin, C. Giacomelli, R.M. Ribeiro-do-Valle, and A. Spinelli, Redox Rep. 6 (2001) 243-250.
]]> 5. M. Nardini, P. Pisu, V. Gentili, F. Natella, M. Di Felice, E. Piccolella, and C. Scaccini, Free Radic. Biol. Med. 25 (9) (1998) 1098–1105.6. H. Fulcrand, A. Cheminat, R. Brouillard, V. Cheynier, Phytochemistry 35 (1994) 499-505.
7. S.A.S.S. Gomes and M.J.F. Rebelo, Sensors 3 (2003) 166-175.
8. S.A.S.S. Gomes, J.M.F. Nogueira, M.J.F. Rebelo, Biosens. Bioelectr. 20 (6) (2004) 1211-1216.
9. C. Giacomelli, K. Ckless, D. Galato, F.S. Miranda, A. Spinelli, J. Braz. Chem. Soc. 13(3) (2002) 332-338.
10. J.M.D. Markovic´, L.M. Ignjatovic´, D. Markovic´, J.M. Baranac, J. Electroanal. Chem. 553 (2003) 169-175.
11. P. Hapiot, A. Neudeck, J. Pinson, H. Fulcrand, P. Neta, C. Rolando, J. Electroanal. Chem. 405 (1996) 169-176.
12. H. Hotta, S. Nagano, M. Ueda, Y. Tsujino, J. Koyama, T. Osakai, Biochim. Bioph. Acta 1572 (2002) 123– 132.
13. M.-E. Ghica, A.M.O. Brett, Electroanalysis 17(4) (2005) 313-318.
14. P.A. Kilmartin, H. Zou, A.L. Waterhouse, J. Agric. Food Chem. 49 (2001) 1957-1965.
]]> 15. C. Lamy, E.M. Belgsir, J.M. Léger, J. Appl. Electrochem. 31 (2001) 799-809.16. S. Andreescu, D. Andreescu, O.A. Sadik, Electrochem. Comm. 5 (2003) 681-688.
17. P. Janeiro, A.M.O. Brett, Anal. Chim. Acta 518 (2004) 109 – 115.
18. C. Giacomelli, F.C. Giacomelli, L.O. Alves, A.K. Timbola, A. Spinelli, J. Braz. Chem. Soc. 15(5) (2004) 748-755.
19. M. Born, P.-A. Carrupt, R. Zini, F. Brée, J.-P. Tillement, K. Hostettmann, B. Testa, Helv. Chim. Acta 79 (1996) 1147-1158.
*Corresponding author. E-mail address: mjrebelo@fc.ul.pt
]]>