Synthesis, characterization and biological activities of some indole derivatives and their metal complexes / Mohamed Mustafa Mohamed Ibrahim

Ibrahim, Mohamed Mustafa Mohamed (2010) Synthesis, characterization and biological activities of some indole derivatives and their metal complexes / Mohamed Mustafa Mohamed Ibrahim. PhD thesis, University of Malaya.

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Abstract

Tryptamine (1H-indole-3-ethyleneamine) Schiff bases were prepared by the condensation reaction of ethanolic solution of tryptamine with: salicylaldehyde (TS), 5 chlorosalicylaldehyde (TCS), 5-nitrosalicylaldehyde (TNS), 3,5-di-tert-butyl-2-hydroxy benzaldehyde (TTET) and the ketones: 2-hydroxyacetophenone (THAP), 5-methyl-2- hydroxyacetophenone (TMeHAP), 5-methoxy-2 hydroxyacetophenone (TOMeHAP), 5- chloro-2-hydroxyacetophenone (TClHAP) and 5-bromo-2 hydroxyacetophenone (TBrHAP). The ligands were coordinated to Zn(II), Cu(II) and Ni(II) by the reaction of metal acetates with the corresponding ligand in a 1 : 2 metal to ligand ratio. The solid products formed were collected, washed with ethanol and recrystallized from a suitable solvent. All the ligands and complexes prepared have been characterized by spectroscopic methods using IR, 1H and 13C {1H} NMR spectroscopies, and UV-Visible spectrophotomerty. Single crystal X-ray structure analysis was carried out for TNS, (TS)2Zn complex, (TS)2Ni complex, (TCS)2Zn complex, (TTET)2Zn complex and (THAP)2Zn complex. Metal content was determined using atomic absorption spectroscopy. X-ray diffraction crystallography for (TNS) shows that it was exists in the zwitterionic form with the phenol H atom transferred to the imine group. Adjacent zwitterions are linked into a linear chain running along the axis by an indole–hydroxy N—H···O hydrogen bond. For zinc complexes the zinc atom is N, O-chelated by two deprotonated Schiff base monoanionic ligands in tetrahedral coordination geometry. In the case of nickel complex, Bis{2-[2-(1H-indol-3-yl)ethyliminomethyl] phenolato k2N,O}nickel(II) N,N-dimethylformamide disolvate the nickel atom lies on a twofold rotation axis. It is N, O-chelated by the deprotonated Schiff base in a square-planar coordination environment. The molecule is linked to a solvent molecule by an indole– dimethylformamide NH···O hydrogen bond. Anti-ulcerogenic activities of the ligands and complexes have been investigated with Cimetidine as a standard drug. The screening was done on high and low doses (60 mg/kg and 30 mg/kg) respectively on six albino Sprague-Dawley rats in which ulcer was induced after dosing by absolute ethanol. The ulcer lesion of the stomachs were identified and counted, and then correlation between the different compound effects has been made.(TS)2Zn complex proved to be more effective in ulcer inhibition than its nickel and copper congeners.The anti-oxidant properties for the prepared ligands and complexes have been evaluated against vitamin C and BHT as standard drugs. The complexes show comparable scavenging activity against DPPH radical than do the ligands. Copper complexes reveal the strongest radical scavenging activity among the compounds. However, none of the compounds were found to be better than vitamin C or BHT. (TTET)2Zn, (TTET)2Cu complexes and TOMeHAP ligand exhibit better ferric reducing abilities than BHT in the FRAP assay. Acute toxicity studies proved that most of the prepared compounds were non-toxic and can be considered as safe.

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