title: Synthesis, characterization and biological activity of Cu(II), Ni(II) and Zn(II) complexes of biopolymeric Schiff bases of salicylaldehydes and chitosan.
abstract: Schiff bases have been prepared from biopolymer chitosan and salicylaldehyde, 5-methoxysalicylaldehyde, and 5-nitrosalicylaldehyde. Ligands were synthesized in a 1:1.5mol ratio, and their Cu(II), Ni(II) and Zn(II) complexes in a 1:1mol ratio (ligand:metal). Ligands were characterized by1H NMR and FTIR, resulting in degrees of substitution from 43.7 to 78.7%. Complexes were characterized using FTIR, electronic spectra, XPRD. The compounds were confirmed by the presence of an imine bond stretching in the 1630-1640cm-1and νMetal-N and νMetal-O at <600cm-1. Electronic spectra revealed that both Cu(II) and Ni(II) complexes present a square plane geometry. The crystallinity values were investigated by X-ray powder diffraction. Thermal behavior of all compounds was evaluated by TGA/DTG and DTA curves with mass losses related to dehydration and decomposition, with characteristic events for ligand and complexes. Schiff base complexes presented lower thermal stability and crystallinity than the starting chitosan. Residues were the metallic oxides as confirmed by XPRD, whose amounts were used in the calculation of the percentage of complexed metal ions. Surface morphologies were analyzed with SEM-EDAX. Preliminary cytotoxicity tests were performed using MTT assay with HeLa cells. Despite the differences in solubility, the free bases presented relatively low toxicity.
authors.affiliation: Instituto de Química de São Carlos, Universidade de São Paulo, Av. Trabalhador São-Carlense 400, 13566-590, São Carlos, SP, Brazil.
authors.forename: Eliene Leandro
authors.initials: EL
authors.lastname: de Araújo
authors.affiliation: Instituto de Química de São Carlos, Universidade de São Paulo, Av. Trabalhador São-Carlense 400, 13566-590, São Carlos, SP, Brazil.
authors.forename: Hellen Franciane Gonçalves
authors.initials: HF
authors.lastname: Barbosa
authors.affiliation: Universidade Federal de São Carlos, Via Washington Luis, Km 235, 13560-900, São Carlos, SP, Brazil.
authors.forename: Edward Ralph
authors.initials: ER
authors.lastname: Dockal
authors.affiliation: Instituto de Química de São Carlos, Universidade de São Paulo, Av. Trabalhador São-Carlense 400, 13566-590, São Carlos, SP, Brazil. Electronic address: cavalheiro@iqsc.usp.br.
authors.forename: Éder Tadeu Gomes
authors.initials: ÉT
authors.lastname: Cavalheiro
mesh_terms: D000447:Aldehydes / Q000737:chemistry*; D002470:Cell Survival / Q000187:drug effects; D060326:Chemistry Techniques, Synthetic; D048271:Chitosan / Q000737:chemistry*; D003300:Copper / Q000737:chemistry; D006367:HeLa Cells; D006801:Humans; D008024:Ligands; D009532:Nickel / Q000737:chemistry; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology*; D012545:Schiff Bases / Q000737:chemistry; D015032:Zinc / Q000737:chemistry
chemical_list: D000447:Aldehydes; D008024:Ligands; D009942:Organometallic Compounds; D012545:Schiff Bases; C013243:salicylaldehyde; D003300:Copper; D009532:Nickel; D048271:Chitosan; D015032:Zinc
keywords: Biological activity; Chitosan; Schiff bases