Photo‐cidnp as a Tool for the Study of the Reactivity of Photosensitizing Drugs: The Furocoumarins

Abstract

Abstract— Several monofunctional and bifunctional furocoumarin derivatives were studied by means of the photo‐CIDNP technique. Nuclear spin polarizations were observed on some of these derivatives when irradiated in acetonitrile solutions. The likely occurrence of both semi‐reduced and semi‐oxidized species of the FC in the reaction scheme is discussed. When N‐acetyltyrosine was added to the solution, CIDNP effects were observed on both reactants. They arose from a highly reversible pathway, as no photoproduct was polarized. On the FC part, the stronger effects were always observed on the 3,4 pyrone double bond suggesting that it must possess the highest spin density in the reaction intermediate. According to previous studies, the latter should be the FC anion or neutral radical. For the amino‐acid moiety, the intensity of the polarizations was strongly dependent on the nature of the FC. This allowed the classification of the FC into three groups (zero, weak and strong intensities). As compared with their photobiological reactivity, this classification seemed to be related to the usual mono‐ and bifunctional distinction. This is the second example showing that photo‐CIDNP could be used as a preliminary test for the study of the photosensitizing drug properties.

Photo‐cidnp Evidence for Charge‐transfer Interaction Between Synthetic Water‐soluble Porphyrins and Guanine*

“…As we were interested in the study of the primary photoprocesses occurring with the photosensitizing drugs by means of the photo-CIDNP technique, we have investigated the behaviour of several porphyrins. Photo-CIDNP allowed us to obtain information on the radical photoreactions ('Type I' reactions) with two series of drugs: the phenothiazine tranquilizers (Marko et al, 1983(Marko et al, , 1985 and the furocoumarins used in skin diseases PUVA therapy (Marko et al, 1987). It has been proven a valuable tool to get mechanistic details on the reactions or for the identification of new photoproducts.…”