PHOTOCHEMISTRY AND PHOTOBIOLOGICAL PROPERTIES OF DICLORAN, A POST-HARVEST FUNGICIDE WITH PHOTOSENSITIZING SIDE-EFFECTS

Francisco Bosca¹, Miguel A. Miranda¹ *, Gabriel Serrano² and Franklin Vargas³

1Departamento de Qumica/Instituto de Tecnologa Qumica UPV-CSIC, Universidad Politcnica de Valencia, Avenida de los Naranjos s/n, 46022-Valencia, Spain.

2Departamento de Dermatologa (Unidad de Fotobiologa), Hospital General Universitario de Valencia, E-46071 Valencia, Spain.

3Centro de Quimica, Instituto Venezolano de Investigaciones Cientificas IVIC, Apartado 21827, Caracas 1020-A, Venezuela.

Abstract -- Photochemical and laser flash photolysis studies on dicloran have shown that this fungicide undergoes photoreactions such as photoreduction of the nitro group and homolytic rupture of the C-NH2 bond. Dramatic changes in the dicloran photoreativity by the influence of the solvents have been observed. A more efficient photodegradation of this fungicide was observed in diethyl ether and chloroform than in methanol or acetonitrile. Photoreduction of the nitro group from dicloran triplet state seems to be the most important photodegradation pathway in solvents of low polarity. Hydrogen abstraction by the triplet state or the intermediate radicals appears to be in the origin of linoleic acid peroxidations photosensitized by dicloran. The photohemolysis assay has been used, as an in-vitro phototoxicity test, to evidence the involvement of radical-mediated cellular membrane damage in the skin photosensitization by dicloran.