title: Enhancing the photocytotoxic potential of curcumin on terpyridyl lanthanide(III) complex formation.
abstract: Lanthanide(III) complexes [Ln(R-tpy)(cur)(NO3)2] (Ln = La(III) in 1, 2; Gd(III) in 5, 6) and [Ln(R-tpy)(scur)(NO3)2] (Ln = La(III) in 3, 4; Gd(III) in 7, 8), where R-tpy is 4′-phenyl-2,2′:6′,2′′-terpyridine (ph-tpy in 1, 3, 5, 7), 4′-(1-pyrenyl)-2,2′:6′,2′′-terpyridine (py-tpy in 2, 4, 6, 8), Hcur is curcumin (in 1, 2, 5, 6) and Hscur is diglucosylcurcumin (in 3, 4, 7, 8), were prepared and their DNA photocleavage activity and photocytotoxicity studied. Complexes [La(ph-tpy)(cur)(NO3)2] (1) and [Gd(ph-tpy)(cur)(NO3)2] (5) were structurally characterized. The complexes in aqueous-DMF showed an absorption band near 430 nm and an emission band near 515 nm when excited at 420 nm. The complexes are moderate binders to calf-thymus DNA. They cleave plasmid supercoiled DNA to its nicked circular form in UV-A (365 nm) and visible light (454 nm) via (1)O2 and ˙OH pathways. The complexes are remarkably photocytotoxic in HeLa cells in visible light (λ = 400–700 nm) and are non-toxic in the dark. FACScan analysis of the HeLa cells treated with 2 and 4 showed cell death via an apoptotic pathway. Nuclear localization of 1–4 is evidenced from confocal imaging on HeLa cells. The hydrolytic instability of curcumin gets significantly reduced upon binding to the lanthanide ions while retaining its photocytotoxic potential.
authors.affiliation: Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore-560 012, India.
authors.forename: Akhtar
authors.initials: A
authors.lastname: Hussain
authors.forename: Kumar
authors.initials: K
authors.lastname: Somyajit
authors.forename: Bhabatosh
authors.initials: B
authors.lastname: Banik
authors.forename: Samya
authors.initials: S
authors.lastname: Banerjee
authors.forename: Ganesh
authors.initials: G
authors.lastname: Nagaraju
authors.forename: Akhil R
authors.initials: AR
authors.lastname: Chakravarty
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002417:Cattle; D056831:Coordination Complexes / Q000737:chemistry* / Q000633:toxicity; D018360:Crystallography, X-Ray; D003474:Curcumin / Q000737:chemistry*; D004247:DNA / Q000378:metabolism; D053837:DNA Cleavage; D005682:Gadolinium / Q000737:chemistry; D006367:HeLa Cells; D006801:Humans; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D007811:Lanthanum / Q000737:chemistry; D008027:Light; D008968:Molecular Conformation
chemical_list: D056831:Coordination Complexes; D028581:Lanthanoid Series Elements; D007811:Lanthanum; D004247:DNA; C427203:calf thymus DNA; D005682:Gadolinium; D003474:Curcumin