Molecular aspects of furocoumarin reactions: Photophysics, photochemistry, photobiology, and structural analysis

Since furocoumarin derivatives absorb UVA light and act as photosensitizers, they have been used as helpful molecular probes and as skin disease drugs. The versatility of these compounds is entirely due to their optical properties. The photoexcited furocoumarins react with biomolecules, especially with pyrimidine bases in DNA, and form mono- and di-adducts. [2 + 2] Photocycloaddition reactions play an important role in the formation of mono- and di-adducts. The degree of photobinding in furocoumarins depends on the types of coumarin compounds, the DNA base sequences, the UVA light doses, excitation wavelengths, temperatures, solvents, and other factors. Consequently, choosing the appropriate conditions can easily control the photoreaction. Furocoumarins have been widely employed for many purposes, and the development of the understanding of their photobiology is still in progress.