title: Photocytotoxic oxovanadium(IV) complexes showing light-induced DNA and protein cleavage activity.
abstract: Oxovanadium(IV) complexes [VO(L)(B)]Cl(2) (1-3), where L is bis(2-benzimidazolylmethyl)amine and B is 1,10-phenanthroline (phen), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq) or dipyrido[3,2-a:2',3'-c]phenazine (dppz), have been prepared, characterized, and their photo-induced DNA and protein cleavage activity studied. The photocytotoxicity of complex 3 has been studied using adenocarcinoma A549 cells. The phen complex 1, structurally characterized by single-crystal X-ray crystallography, shows the presence of a vanadyl group in six-coordinate VON(5) coordination geometry. The ligands L and phen display tridentate and bidentate N-donor chelating binding modes, respectively. The complexes exhibit a d-d band near 740 nm in 15% DMF-Tris-HCl buffer (pH 7.2). The phen and dpq complexes display an irreversible cathodic cyclic voltammetric response near -0.8 V in 20% DMF-Tris-HCl buffer having 0.1 M KCl as supporting electrolyte. The dppz complex 3 exhibits a quasi-reversible voltammogram near -0.6 V (vs SCE) that is assignable to the V(IV)-V(III) couple. The complexes bind to calf thymus DNA giving binding constant values in the range of 6.6 x 10(4)-2.9 x 10(5) M(-1). The binding site size, thermal melting and viscosity binding data suggest DNA surface and/or groove binding nature of the complexes. The complexes show poor "chemical nuclease" activity in dark in the presence of 3-mercaptopropionic acid or hydrogen peroxide. The dpq and dppz complexes are efficient photocleavers of plasmid DNA in UV-A light of 365 nm via a mechanistic pathway that involves formation of both singlet oxygen and hydroxyl radicals. The complexes show significant photocleavage of DNA in near-IR light (>750 nm) via hydroxyl radical pathway. Among the three complexes, the dppz complex 3 shows significant BSA and lysozyme protein cleavage activity in UV-A light of 365 nm via hydroxyl radical pathway. The dppz complex 3 also exhibits photocytotoxicity in non-small cell lung carcinoma/human lung adenocarcinoma A549 cells giving IC(50) value of 17 microM in visible light (IC(50) = 175 microM in dark).
authors.affiliation: Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560012, India.
authors.forename: Pijus K
authors.initials: PK
authors.lastname: Sasmal
authors.forename: Sounik
authors.initials: S
authors.lastname: Saha
authors.forename: Ritankar
authors.initials: R
authors.lastname: Majumdar
authors.forename: Rajan R
authors.initials: RR
authors.lastname: Dighe
authors.forename: Akhil R
authors.initials: AR
authors.lastname: Chakravarty
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry / Q000187:drug effects*; D004249:DNA Damage; D004354:Drug Screening Assays, Antitumor; D006801:Humans; D008027:Light; D008958:Models, Molecular; D015394:Molecular Structure; D009113:Muramidase / Q000737:chemistry* / Q000378:metabolism; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D017319:Photosensitizing Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D013329:Structure-Activity Relationship; D014638:Vanadates / Q000737:chemistry*
chemical_list: D009942:Organometallic Compounds; D017319:Photosensitizing Agents; C075743:oxovanadium IV; D012710:Serum Albumin, Bovine; D014638:Vanadates; D004247:DNA; C427203:calf thymus DNA; D009113:Muramidase