Photochemical interaction between xanthyletine and DNA.

Abstract— Xanthyletine, a dimethyl‐pyranocoumarin having a structural relationship to psoralen, has been studied in connection with its interaction with DNA. In the dark, it forms a weak molecular complex with DNA, which is not of the intercalated type. Under irradiation at 365nm, it is able to bind covalently to DNA, with, however, a much lower rate relative to psoralen. In this photobinding, it behaves as a pure monofunctional reagent, involving only its3,4‐double bond of the α‐pyronic ring. 3‐(α,α‐dimethyl‐allyl)‐xanthyletine, studied for a comparison, showed only a very low photoreactivity with DNA for covalent addition; this is attributed to the presence of a bulky group at position3, which prevents almost completely the photoreaction of the3,4‐double bond. Because of the low capacity of photobinding with DNA and the inability to form cross‐links, the photobiological effects of xanthyletine are accordingly reduced: Inhibition of DNA and RNA synthesis in Ehrlich ascites tumor cells, killing of E. coli bacterial cells, inactivation of T2 bacteriophage have been observed. By contrast, it was inactive in producing erythema on guinea pig skin. Copyright © 1979, Wiley Blackwell. All rights reserved