Photosensitizing properties of triplet beta-lapachones in acetonitrile solution.

The photochemical reactivity of beta-lapachone (1), nor-beta-lapachone (2) and 1,2-naphthoquinone (3) towards amino acids and nucleobases or nucleosides has been examined employing the nanosecond laser flash photolysis technique. Excitation (lambda = 355 nm) of degassed solutions of 1-3, in acetonitrile, resulted in the formation of their corresponding triplet excited states. These transients were efficiently quenched by l-tryptophan, l-tryptophan methyl ester, l-tyrosine, l-tyrosine methyl ester and l-cysteine (k(q) approximately 10(9) L mol(-1) s(-1)).