Psoralen Molecule Research Articles

Recent studies (1) on 8-Methoxypsoralen (Xanthotoxin, “Methoxsalen” or “8-MOP) have created interest in chemical agents which augment the skin pigmentation of normal as well as vitiligenous persons. The photosensitizationf elicited by these substances has focused attention on the mechanism of this phenomenon (2, 3). In the presence of long-wave ultraviolet radiation, many of these psoralen derivatives, which are generally known as furocoumarins, evoke changes on mammalian skin manifested by erythema and increased pigmentation. Furthermore, these substances inhibit a number of enzymes both in vivo and in vitro (4). Musajo and associates (5, 6) have investigated the photosensitizing activity of various furocoumarins following topical application of 25 pig/cm2 on human skin. Their studies have shown that psoralen was the most active of the naturally occurring furocoumarins. In earlier communications of this series Pathak and Fitzpatrick (7, 8) confirmed these observations and reported the photosensitizing activity of a number of substituted psoralens. Substitution with methoxy-, nitro-, amino-, or hydroxy-at 5 or 8 positions resulted in partial or complete loss of the photosensitizing response of the parent psoralen. Likewise, hydrogenation at 4', 5' resulted in complete loss of activity. It was also shown that coumarin derivatives were inactive. Finally, it was demonstrated that a linear fusion of furan and coumarin rings, as in the psoralen molecule, was essential for this response; a non-linear structure like isopsoralen had no photosensitizing action.