4,5‘‐DIMETHYLANGELICIN: A NEW DNA‐PHOTOBINDING MONOFUNCTIONAL AGENT*

Abstract

Abstract— 4,5′‐Dimethylangelicin is a new angular furocoumarin showing interesting photochemical and photosensitizing properties. In the dark it forms a complex with native DNA having higher values of the binding parameters than angelicin; by irradiation at 365 nm it is able to photobind with DNA several times faster than angelicin and in about the same degree as psoralen, without forming crosslinkages. It therefore behaves as a pure monofunctional reagent. The same high photobinding capacity with DNA is shown also in vivo in Ehrlich ascites tumor cells and bacterial E. coli cells. 4,5′‐Dimethylangelicin is very active in inhibiting the DNA and RNA syntheses in Ehrlich ascites tumor cells alter irradiation at 365 nm, much more so than angelicin and in the same degree as psoralen. It is also more active than angelicin in decreasing the tumor transmitting capacity of the same cells and the colony‐forming ability of E. coli cells, although to a lesser degree than psoralen. It is ineffective in producing erythema on guinea‐pig skin. The involvement of repair processes of DNA in these photosensitized effects is discussed.