PHOTOBIOLOGICAL ACTIVITY OF SULFUR AND SELENIUM ANALOGS OF PSORALEN

Eight psoralen analogues, in which sulphur or selenium replaces one or both intracyclic oxygen atoms, were synthesized. Photoreaction with M 13mp19 RF DNA in the presence and absence of oxygen (wavelength, great er than 320 nm) was studied. The damaged viral DNA was transfected int o Escherichia coli and scored for infectivity towards Ca-treated wild- type E. coli. This allowed a comparative evaluation to be made of the heteropsoralens in terms of the photoreaction with DNA and the photody namic effect. Most of the seleno- and thio-psoralens show very high ph otoactivity towards DNA compared with psoralen and 8-methoxypsoralen ( 8-MOP). Their photoreactivity is due mainly to a [2+2] photoreaction, since only a minor influence of molecular oxygen could be detected. So me of the studied seleno- and thio-psoralens are very efficient DNA ph otoinactivating agents and show great promise in photochemotherapy.