title: Metal based photosensitizers of tetradentate Schiff base: promising role in anti-tumor activity through singlet oxygen generation mechanism.
abstract: In the present investigation, a Schiff base N'(1),N'(3)-bis[(Z)-(2-hydroxynapthyl)methylidene]benzene-1,3-dicarbodihydrazide (L1) and its Co(II), Ni(II) and Cu(II) complexes have been synthesized and characterized as novel photosensitizing agents for photodynamic therapy (PDT). The interaction of these complexes with calf thymus DNA (CT DNA) has been explored using absorption, thermal denaturation and viscometric studies. The experimental results revealed that Co(II) and Ni(II) complexes on binding to CT DNA imply a covalent mode, most possibly involving guanine N7 nitrogen of DNA, with an intrinsic binding constant Kb of 4.5×10(4)M(-1) and 4.2×10(4)M(-1), respectively. However, interestingly, the Cu(II) complex is involved in the surface binding to minor groove via phosphate backbone of DNA double helix with an intrinsic binding constant Kb of 5.7×10(4)M(-1). The Co(II), Ni(II) and Cu(II) complexes are active in cleaving supercoiled (SC) pUC19 DNA on photoexposure to UV-visible light of 365nm, through (1)O2 generation with quantum yields of 0.28, 0.25 and 0.30, respectively. Further, these complexes are cytotoxic in A549 lung cancer cells, showing an enhancement of cytotoxicity upon light irradiation.
authors.affiliation: Department of Studies and Research in Industrial Chemistry, Kuvempu University, Shankaraghatta 577 451, Shimoga, India.
authors.forename: S M
authors.initials: SM
authors.lastname: Pradeepa
authors.forename: H S
authors.initials: HS
authors.lastname: Bhojya Naik
authors.forename: B
authors.initials: B
authors.lastname: Vinay Kumar
authors.forename: K
authors.initials: K
authors.lastname: Indira Priyadarsini
authors.forename: Atanu
authors.initials: A
authors.lastname: Barik
authors.forename: T R
authors.initials: TR
authors.lastname: Ravikumar Naik
authors.forename: M C
authors.initials: MC
authors.lastname: Prabhakara
mesh_terms: D000042:Absorption; D000818:Animals; D000970:Antineoplastic Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D001572:Benzofurans / Q000737:chemistry; D002417:Cattle; D016923:Cell Death / Q000187:drug effects / Q000528:radiation effects; D045744:Cell Line, Tumor; D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D004247:DNA / Q000378:metabolism; D053837:DNA Cleavage / Q000187:drug effects; D004578:Electron Spin Resonance Spectroscopy; D004587:Electrophoresis, Agar Gel; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009691:Nucleic Acid Denaturation / Q000187:drug effects / Q000528:radiation effects; D017319:Photosensitizing Agents / Q000494:pharmacology*; D010957:Plasmids / Q000378:metabolism; D012545:Schiff Bases / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D026082:Singlet Oxygen / Q000737:chemistry / Q000378:metabolism*; D013055:Spectrophotometry, Infrared; D013481:Superoxides / Q000378:metabolism; D013696:Temperature; D013816:Thermodynamics; D014466:Ultraviolet Rays; D014783:Viscosity
chemical_list: D000970:Antineoplastic Agents; D001572:Benzofurans; D056831:Coordination Complexes; D017319:Photosensitizing Agents; D012545:Schiff Bases; D013481:Superoxides; D026082:Singlet Oxygen; C011238:1,3-diphenylisobenzofuran; D004247:DNA; C427203:calf thymus DNA
keywords: Cytotoxicity; DNA photocleavage; Photosensitizer; Schiff base; Singlet oxygen