Synthesis, Structural Characterization and Evaluation of the Chelating Potential in C. Elegans Involving Complexes of Mercury (Ii) with Schiff Bases Derived from Amino Acids
33 Pages Posted: 28 May 2020
Two series of neutral mercury(II) complexes have been obtained from the reaction of HgPh(OCOCH 3 )( 1 , 2 , and 3 ) or Hg(OCOCH 3 ) 2 ( 4 , 5 , and 6 ) with N-(2-hydroxynaphtalidene)β-alanine (L1H 2 ), N-(5-bromo-salicylidene)β-alanine (L2H 2 ), and N-(5-bromo-salicylidene)β-phenylalanine (L3H 2 ), respectively. The complexes were characterized by elemental analysis, IR, NMR ( 1 H, 13 C, and 199 Hg) and X-ray crystallography ( 1 and 2 ). X-ray diffraction analyses are similar for complexes 1 and 2 , consistent with mononuclear compounds bearing a primarily di-coordinated Hg II nucleus with several additional Hg—O interactions, which give rise to supramolecular assemblies. Solution NMR analyses indicate that the primary coordination is retained in DMSO for 1 , 2 and 3 , but the additional interactions observed in solid state are lost in solution. Complexes 4 , 5 and 6 are also mononuclear and all analyses, both in solution and solid state, point to a di-coordinated Hg II nucleus with a di-anionic Schiff base ligand. The biological evaluation of the Schiff base (L1H 2 ) chelating potential was performed by pretreating Caenorhabditis elegans ( C. elegans ) nematodes with the L1H 2 (1mM) followed by phenylmercury acetate exposure (LC 50 = 290 μM).The pretreatment with L1H 2 resulted in a significant protection of worm survival against phenylmercury acetate toxicity. Together, these data show that the chelating potential of these ligands is a crucial factor in reducing the toxic effects caused by metals in the worm, suggesting them as promising agents in chelation therapy.
Keywords: Schiff bases, amino acids, mercury(II) complexes, crystal structures, 199Hg NMR spectroscopy, Caenorhabditis elegans, chelating potential.
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