Ferrocenyl-contained dendritic-like antioxidants with dihydropyrazole and pyrazole as the core: investigations into the role of ferrocenyl group and structure–activity relationship on scavenging radical and protecting DNA

Eight ferrocenyl and three corresponding phenyl dendritic-like antioxidants with dihydropyrazole or pyrazole as the core were synthesized and their antioxidant abilities to scavenge 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) cationic radical (ABTS+radical dot) and to protect DNA against 2,2′-azobis(2-amidinopropane hydrochloride) (AAPH)-induced oxidation were evaluated. It was found that the antioxidant abilities of almost all of the ferrocenyl dendritic-like antioxidants are greater than those of the corresponding phenyl dendritic-like antioxidants remarkably. Moreover, the structure–activity relationships of all these dendritic-like antioxidants were investigated in detail. The quantitative contributions of ferrocenyl group, hydroxyl group, and dihydro-structure in the heterocyclic core to the values of n, napp and n+napp in scavenging ABTS+radical dot and the values of n in protecting DNA against AAPH-induced oxidation were also calculated.