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Title of Thesis

Uzma Muhammad Ashiq
Institute/University/Department Details
Department of Chemistry/ University of Karachi
Number of Pages
Keywords (Extracted from title, table of contents and abstract of thesis)
vanadium, hydrazide, antidiabetic agent, ligands, aqueous oxovanadium, leishmaniasis, fungal infections, ureases, phosphodiesterases, α-glucosidases, thymidine phosphorylase

Vanadium plays an important role in biological systems and exhibits variety of bioactivities. In an effort to uncover the chemistry and biochemistry of vanadium with nitrogen and oxygen containing ligands, Synthesis, characterization, enzyme inhibition. microbial and antioxidant studies of vanadium(IV) complexes with hydrazide ligands is reported here. Substituents on these ligands exhibit systematic variations of electronic and steric factors. Elemental and spectral data indicates the presence of a dimeric unit with two vanadium(IV) ions coordinated with two hydrazide ligands along with two water molecules. The magnetic properties support the dimeric nature of the complexes in solid state. The magnetic moments are in the range of 1.10 to 1.54 B.M. which are lower than that exhibited by one unpaired electron of V(IV) complexes. Similar magnetic moments of different complexes may indicate existence of similar structures of the complexes. The complexes exhibit molar conductivity in DMSO in the range of 32.20 to 148.30 ohm-1 cm2 mol-1 It falls into the range of 1:1 ionic ratio suggesting non coordination of the sulfate ion and supports the formation of outer-sphere complex.

The stability studies of these complexes over time in coordinating solvent, DMSO, indicates binding of the solvent molecules to give [V2O2L2(H2O)2(DMSO)2]2+ (L = hydrazide ligand) and then conversion of it to a monomeric intermediate species, [VOL(DMSO)3]1+. All complexes are stable for at least twelve hours whereas, after that different complexes exhibit very different behavior. Most of the ligands are inactive against snake venom phosphodiesterase I (SVPDE). urease. α-glucosidase and thymidine phosphorylase. whereas, after coordination with vanadium they show very promising inhibitory potential against these enzymes and were found to be non-competitive inhibitors. To understand the role of these complexes towards free radicals which play important role in several diseases including diabetes and its complications, we studied free radical scavenging properties of these complexes against DPPH, superoxide and nitric oxide free radical. The ligands are inactive in case of superoxide and nitric oxide whereas active against DPPH radical, however, the complexes show promising inhibitory activity for all free radicals. These complexes also show low phytotoxicity. Bactericidal, leishmanicidal, fungicidal microbial activities shows varying degree of activities for hydrazides and their complexes. Structure activity relationship studies indicate that the steric and/or electronic effects that may change the geometry of the complexes play an important role in their inhibitory potential, radical scavenging activity and phytotoxicity.

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S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents
358.03 KB
2 1 The Chemistry And Biochemistry Of Vanadium In Aqueous And Nonaqueous Solution 1
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  1.1 Natural Occurrences Of Vanadium 1
  1.2 Aqueous Oxovanadium Chemistry 2
  1.3 Aqueous Interactions Of Vanadium (IV) And (V) In Aqueous Solutions With Ligands 7
  1.4 Nonaqueous Vanadium (IV) And Vanadium (V) Chemistry 15
  1.5 Toxicity Of Vanadium Compounds In Humans And Animals 16
  1.6 Insulin Like Properties Of Vanadium Complexes 16
  1.7 Anticancer Properties Of Vanadium Complexes 19
  1.8 Model Studies; Enzymes, Substrates, Inhibitors And Natural Products 24
  1.9 Catalytic Applications Of Vanadium Complexes 24
  1.10 Complexes Of Vanadium With Hydrazides ; Potential Antidiabetic Agents 25
3 2 Experimental Studies Of Vanadium Complexes 44
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  2.1 Materials 44
  2.2 Physical Measurements 44
  2.3 Synthesis 46
4 3 Chemistry Of Vanadium Hydrazide Complexes: Results And Discussion 58
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  3.1 Synthesis 58
  3.2 Spectroscopy 61
5 4 Enzyme Inhibition Studies Of Oxovanadium (IV)- Hydrazide Complexes 87
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  4.1 Ureases 87
  4.2 Phosphodiesterases 100
  4.3 ‘-Glucosidases 112
  4.4 Thymidine Phosphorylase 121
6 5 Antioxidant Studies Of Oxovanadium (IV)- Hydrazide Complexes With Radical Scavenging Assays( DPPH), Superoide And Nitric Oxide) 129
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  5.1 Reactive Oxygen Species (ROS ) 129
  5.2 Antioxidants 30
  5.3 Experimental 135
  5.4 Results And Discussion 138
7 6 Bioactivity Study Of Vanadium( IV) Complexes 149
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  6.1 Leishmaniasis 150
  6.2 Fungal Infections 160
  6.3 Phytotoxicity 168
  6.4 Antibacterial Agents 173