Ferrocene-Conjugated L-Tryptophan Copper(II) Complexes of Phenanthroline Bases Showing DNA Photocleavage Activity and Cytotoxicity

Goswami, Tridib K and Chakravarthi, Balabhadrapatruni VSK and Roy, Mithun and Karande, Anjali A and Chakravarty, Akhil R (2011) Ferrocene-Conjugated L-Tryptophan Copper(II) Complexes of Phenanthroline Bases Showing DNA Photocleavage Activity and Cytotoxicity. In: Inorganic Chemistry, 50 (17). pp. 8452-8464.

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Abstract

Ferrocene-conjugated L-tryptophan (L-Trp) reduced Schiff base (Fc-TrpH) copper(II) complexes [Cu(Fc-Trp)(L)](ClO(4)) of phenanthroline bases (L), viz. 2,2'-bipyridine (bpy in 1), 1,10-phenanthroline (phen in 2), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq in 3), and dipyrido[3,2-a:2',3'-c]phenazine (dppz in 4), were prepared and characterized and their photocytotoxicity studied. Cationic reduced Schiff base (Ph-TrpH) complexes [Cu(Ph-Trp)(L)(H(2)O)] (ClO(4)) (L = phen in 5; dppz in 6) having the ferrocenyl moiety replaced by a phenyl group and the Zn(II) analogue (7) of complex 4 were prepared and used as control species. The crystal structures of 1 and 5 with respective square-planar CuN(3)O and square-pyramidal CuN(3)O(2) coordination geometry show significantly different core structures. Complexes 1-4 exhibit a Cu(II)-Cu(I) redox couple near -0.1 V and the Fc(+)-Fc couple at similar to 0.5 V vs SCE in DMF-0.1 M [Bu(4)(n)N] (ClO(4)) (Fc = ferrocenyl moiety). The complexes display a copper(II)-based d-d band near 600 nm and a Fc-centered band at similar to 450 nm in DMF-Tris-HCl buffer. The complexes are efficient binders to calf thymus DNA. They are synthetic chemical nucleases in the presence of thiol or H(2)O(2), forming hydroxyl radicals. The photoactive complexes are cleavers of pUC19 DNA in visible light, forming hydroxyl radicals. Complexes 2-6 show photocytotoxicity in HeLa cancer cells, giving IC(50) values of 4.7, 10.2, 1.3, 4.8, and 4.3 mu M, respectively, in visible light with the appearance of apoptotic bodies. The complexes also show photocytotoxicity in MCF-7 cancer cells. Nuclear chromatin cleavage has been observed with acridine orange/ethidium bromide (AO/EB) dual staining with complex 4 in visible light. The complexes induce caspase-independent apoptosis in the HeLa cells.

Item Type:	Journal Article
Publication:	Inorganic Chemistry
Publisher:	American Chemical Society
Additional Information:	Copyright of this article belongs to American Chemical Society.
Department/Centre:	Division of Biological Sciences > Biochemistry Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited:	28 Sep 2011 11:11
Last Modified:	28 Sep 2011 11:11
URI:	http://eprints.iisc.ac.in/id/eprint/40764

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