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

Abstract 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 (12 nm) 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 × 10 6  M −1 . The porphyrin–quinoxaline conjugate 8 displayed enhanced photocytotoxicity (IC 50  = 0.06 μM) when compared to TMPyP against A549 cancer cells.