Photoactivated DNA cleavage and anticancer activity of oxovanadium(IV) complexes of curcumin

Oxovanadium(IV) complexes [VO(Fc-pic)(acac)](ClO4) (1), [VO(Fc-pic)(cur)](ClO4) (2), [VO(Ph-pic)(acac)](ClO4) (3) and [VO(Ph-pic)(cur)](ClO4) (4), where Fc-pic and Ph-pic are ferrocenylmethyl-bis-(2-pyridylmethylamine) (in 1, 2) and bis-(2-pyridylmethyl)benzylamine (in 3, 4), respectively, acac is acetylacetonate anion (in 1, 3) and cur is curcumin anion (in 2, 4) were prepared, characterized and their photo-induced DNA cleavage and anticancer activity studied. The crystal structure of 1 as its PF6− salt (1a) shows the presence of a VO2+ moiety in VO3N3 coordination geometry. The complexes show a d–d band at ∼790 nm in DMF and display V(IV)/V(III) redox couple near −1.45 V vs. SCE in DMF-0.1 M TBAP. The complexes are avid binders to calf thymus DNA. Complex 2 efficiently photo-cleaves plasmid DNA in near-IR light of 785 nm forming OH radicals. The curcumin complexes show photocytotoxicity in HeLa cancer cells in visible light of 400–700 nm with significant cellular uptake within 4 h of incubation time.

Graphical abstractOxovanadium(IV) complexes of curcumin as efficient photocleavers of plasmid DNA in near-IR red light show remarkable photodynamic therapy (PDT) effect in visible light in HeLa cells with low dark cytotoxicity. Confocal microscopy showed their cytosolic and nuclear localization. The hydrolytically unstable curcumin gets stabilized on binding to the VO2+ moiety.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Ferrocene–conjugated oxovanadium(IV) complexes show photocleavage of DNA. ► The curcumin VO2+ complexes show cytotoxicity in HeLa cells in visible light. ► The crystal structure shows a pendant ferrocenyl group and a VO2+ moiety. ► The curcumin ligand gets stabilized on binding to the vanadium(IV) ion. ► The fluorescent curcumin complexes are suitable for the cellular uptake study.