Background: Metal organic compounds have attracted considerable attention since the
advent of Salvarsan, a metal organic compound for the treatment of syphilis. Ferrocene as an effective
phenyl bioisostere is becoming a viable platform for drug design by virtue of its redox properties,
high lipophilicity and three-dimensional metallocene unit, which may lead to some changes in
selectivity toward biological targets compared with phenyl or alkyl groups. Therefore, ferrocene
seems to an appropriate candidate for improving the antioxidant activity of drugs.
Methods: We synthesized four ferrocenyl-containing curcumin analogues by introducing ferrocenyl
groups into the active methylene groups to obtain higher antioxidant activity than the parent ferrocene-
substituted curcumin analogues, and their antioxidant activities were evaluated in 2, 2′-
azobis (2-amidinopropane hydrochloride) (AAPH) and Cu2+/glutathione(GSH) -induced oxidation of
DNA, and in trapping 2, 2′-diphenyl-1-picrylhydrazyl (DPPH), 2, 2′-azinobis(3-ethylbenzothiazoline-
6-sulfonate) cationic radicals (ABTS+•) and galvinoxyl radicals.
Results: These ferrocenyl-containing curcumin analogues can protect DNA against Cu2+/GSHinduced
oxidation, and scavenge 5.7, 6.9, 5.5 and 5.3 radicals in protecting DNA against AAPHinduced
oxidation. Compounds (3)~(5) can trap more DPPH, ABTS+• and galvinoxyl radicals than
compound (6). The substituents and iron atoms play an antioxidant role in ferrocenyl-containing
Conclusion: The introduction of ferrocenyl group results in a higher antioxidant activity than the
traditional hydroxyl-involved curcumin analogues. The ferrocenyl group is a powerful antioxidative
group that could be used to modify natural antioxidants. The electron-accepting group attaching to
the phenyl-group could further increase the antioxidant activity. Ferrocene-containing curcumin
analogues show higher activities in quenching radicals and protecting DNA against radical-induced
oxidation. Therefore, the introduction of ferrocenyl group into the natural antioxidant may contribute
to increase the antioxidant activity.