Synthesis of 4-methylcoumarin derivatives containing 4,5-dihydropyrazole moiety to scavenge radicals and to protect DNA.

Abstract A series of 4-methylcoumarin derivatives containing 4,5-dihydropyrazole moiety were synthesized and their antioxidant activities were evaluated in AAPH (2,2′-azobis(2-amidinopropane hydrochloride))-induced oxidation of DNA, and in trapping DPPH (2,2′-diphenyl-1-picrylhydrazyl) and ABTS +• (2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) cationic radical), respectively. Among coumarin derivatives, 3a – d and 4a – c exhibited the termination of radical propagation-chains in AAPH-induced oxidation of DNA. The ortho dihydroxyphenyl substitution at 5 position and 1-unsubstitution of the 4,5-dihydroxylpyrazole was found enhancing the antioxidant activities of these coumarin derivatives.