Psoralen, photochemistry

Photosensitizers are agents that sensitize cells to radiation in the visible and near ultraviolet region of the radiation spectrum. Therapeutic use has been made of naturally occurring psoralens to treat vitiligo and psoriasis, in so-called photodynamic therapy. With newly developed UV irradiation systems that emit high-intensity UVA radiation, the principle has been extended to the treatment of severe psoriasis, mycosis fungoides and many other skin diseases. Agents used in psoralen photochemistry (PUVA) medicine include methoxypsoralen (8-MOP), trioxysalen and other synthetic psoralens. 

Hearst, J.E. (1982) Psoralen photochemistry and nucleic acid structure, Biorg. Chem., 8, 945-953. 

They have also shown photosensitizing and photo-toxic effects in animals and humans and have been used in photochemotberapy for management of vitiligo, psoriasis, and mycosis fungoides, cf. T. F. Anderson, J. J. Voorhees, Ann. Rev. Pharmacol. Toxicol 20, 235 (1980) A. Korn-bauser et al, Science 217, 733 (1982). Review of psoralen photochemistry B. J. Parsons, Photochem. Photobiol. 32,... 

Cimino, C.P., Camper, H.B., Isaacs, S.T., and Hearst, J.E. (1985) Psoralens as photoactive probes of nucleic acid structure and function Organic chemistry, photochemistry, and biochemistry. Annu. Rev. Biochem. 54, 1151-1193. 

Dall Acqua F, Viola G, Vedaldi D (2004) Cellular and molecular target of psoralen. In Hoorspool WM, Lend F (eds) CRC Handbook of Organic Photochemistry and Photobiology. CRC Press, Boca Raton USA, pp 1-17... 

The whole body of molecular photochemistry can in principle be used when UVA light is adopted (UV B is erythematogeneous) and thus for external treatment. The field that has expanded more rapidly is photochemotherapy (PUVA) mostly based on the use of psoralens or related heterocycles and solar or artificial light against a variety of skin disorders. In long-term treatments, however, there is the risk of premature skin aging and formation of squamous carcinoma cells. Therefore, advanced studies address the issue of safe treatment, e.g., by digitalization of the method [11-13]. 

Scheme of the gas-phase photochemistry of psoralen based on quantum-chemical CASPT2 calculations. Energies are referred to (Sti)min... 

G. D. Cimino, H. B. Gamper, S. T. Isaacs, and J. E. Hearst, Psoralens as photoactive probes of nucleic acid structure and function organic chemistry, photochemistry and biochemistry Annual Review of Biochemistry, vol. 54, pp. 1151-1193, 1985. 

Schmitt, I.M., Chimenti, S., and Gasparro, RR, Psoralen-protein photochemistry a forgotten field, J. Photochem. PhotobioL, B Biol., 27, 101,1995. 

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