Cationic porphyrin–quinoxaline conjugate as a photochemically triggered novel cytotoxic agent

A novel cationic porphyrin–quinoxaline conjugate 8 was prepared in good yield by the coupling of activated quinoxaline carboxylic acid 5 with an appropriate aminoporphyrin. The UV–vis spectra of conjugate 8 with the addition of ctDNA shows substantial hypochromicity (39%) and a red shift (12nm) in the Soret band indicating intercalation and self stacking along the surface. The binding constant of conjugate 8 with ctDNA was determined to be 1.26×106M−1. The porphyrin–quinoxaline conjugate 8 displayed enhanced photocytotoxicity (IC50=0.06μM) when compared to TMPyP against A549 cancer cells.