Design, synthesis and photoinduced DNA cleavage studies of [1,2,4]-triazolo[4,3-a]quinoxalin-4(5H)-ones.

An expedient and eco-friendly synthesis of 1-aryl/heteroaryl-[1,2,4]-triazolo[4,3-a]quinoxalin-4(5H)-ones (4) has been accomplished via iodobenzene diacetate mediated oxidative intramolecular cyclization of 3-(2-(aryl/heteroarylidene)hydrazinyl)-quinoxalin-2(1H)-ones (3). Ten synthesized compounds 3 and 4 (10-40 μg) on irradiation with UV light at λmax 312 nm could lead to cleavage of supercoiled pMaxGFP DNA (Form I) into the relaxed DNA (Form II) without any additive. Further, DNA cleaving ability of triazoles was quantitatively evaluated and was found to be dependent on its structure, concentration, and strictly on photoirradiation time. Mechanistic investigations using several additives as potential inhibitors/activator revealed that the DNA photocleavage reaction involves Type-I pathway leading to formation of superoxide anion radicals (O2-) as the major reactive oxygen species responsible for photocleavage process.