Photo-degradation of <i>trans</i>-caffeic acid in aqueous solution and influence of complexation by metal ions - Archive ouverte HAL
Article Dans Une Revue Journal of Photochemistry and Photobiology A: Chemistry Année : 2013

Photo-degradation of trans-caffeic acid in aqueous solution and influence of complexation by metal ions

Résumé

The photo-degradation of metal complexes of caffeic acid was compared to the photo-degradation of free caffeic acid by using UV-vis spectroscopy and HPLC-ESI-mass spectrometry. This article reports first the determination of the products that are formed from the photo-degradation of trans-caffeic acid in aqueous solution and the investigation of the mechanism by a kinetic approach. The good fit between the model and the experimental concentration profiles confirms the photo-isomerization route of the molecule to cis-caffeic acid which then undergoes a cyclization to form the esculetin photo-product. In addition, it reveals, for the first time, another route of major importance leading to the product vinylcatechol. The presence of oxygen leads to an increase of the photo-isomerization rate. Then we report that metallic cations such as Al(III), Pb(II) and Cu(II) can influence the rate and mechanism of caffeic acid photo-degradation. Al(III) ions slow down the photo-degradation whereas Pb(II) and Cu(II) ions have a promoter effect on the production of esculetin. In all cases, the photo-isomerization is reduced by the presence of metal ions and the formation of vinylcatechol does not occur.

Dates et versions

hal-00835301 , version 1 (18-06-2013)

Identifiants

Citer

A. Le Person, A.S. Lacoste, J.P. Cornard. Photo-degradation of trans-caffeic acid in aqueous solution and influence of complexation by metal ions. Journal of Photochemistry and Photobiology A: Chemistry, 2013, 265, pp.10 - 19. ⟨10.1016/j.jphotochem.2013.05.004⟩. ⟨hal-00835301⟩
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