BIOPHYSICAL AND BIOLOGICAL PROPERTIES OF NEWLY SYNTHESIZED DIOXINOCOUMARIN DERIVATIVES .2. DARK AND PHOTOINDUCED EFFECTS ON T7 PHAGE, YEAST AND HELA-CELLS

The dioxinocoumarin derivatives 5H-[2]benzopyrano-[3,4-g][1,4]benzodioxin-5-one (I), 5H-[2]benzopyrano-[3,-g][2,3]-dihydro-[1,4]benzodioxin-5-one (II), 6H-[2]benzopyrano[3,4-f]-1,4-benzodioxin-6-one (III) and 6H-[2]benzopyrano[3,4-f]-2,3-dihydro-1,4-benzodioxin-6-one (IV) were synthesized. Their biological effect was studied in the presence and absence of UVA radiation, and compared with that of 8-methoxysporalen (8-MOP) and angelicin derivatives on T7 phage, diploid yeast (Saccharomyces cerevisiae) and HeLa cells. The photobiological activities of compounds I and III were stronger than that of 8-MOP in phage inactivation and DNA synthesis inhibition in HeLa cells, whereas compounds II and IV, with a saturated dioxin ring, showed very poor activity. The photosensitizing activity of dioxinocoumarins on phage inactivation decreased by a factor of two to three in the absence of oxygen. Treatments with compound I and UVA in the presence of oxygen modified the helical structure and stability of phage DNA and proteins. Compounds I and II were more active than IV for photoinduced cell killing in yeast, although always less active than 8-MOP. At comparable photocytotoxic levels, compounds I and III were as strong inducers of cytoplasmic ''petite'' mutants in yeast as angelicin, suggesting a possible monofunctional mode of action with cellular DNA.