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Title of Thesis

Faiyaz Hussain Madani Vaid
Institute/University/Department Details
University of Karachi/ Department of Pharmaceutical Chemistry
Number of Pages
Keywords (Extracted from title, table of contents and abstract of thesis)
thiamine hydrochloride, riboflavin, aqueous solution, vitamin b1, thiamine deficiency, hypervitaminosis, thiamine hcl solution

A detailed review of the literature on chemical, biochemical, pharmacological, analytical and degradation studies of thiamine HCl (vitamin B1) has been presented and an investigation of the photolysis of thiamine HCL solutions in the presence absence of riboflavin has been made

Thiamine HCl solutions on UV irradiation at pH 1.0-12.0 give rise to a number of hydrolytic (2-methyl-4-amino-5-hydroxymethylpyrimidine and 4-methyl-5-β-hydroxyethylthiazole) and oxidation (2-methyl-4-amino-5-amino-methylpyrimidine, α-aceto-γ-mercaptopanol and thiochrome) products both in the presence and absence characteristics. A RP-HOLC method with isocratic elution has been developed for the simultaneous determination of thiamine HCl, its photoproducts and riboflavin

The photolysis of thiamine HCl follows an apparent first-order kinetics and the rate constants (kobs) vary from 1.38X10-2 min-1 (pH 1.0) to 0.95 min-1 (pH 12.0) with a maximum value of 2.70X10-2 min-1 (pH 4.0). The second-order rate constants (k2) for the bimolecular interaction of thiamine HCl and riboflavin range from 1.60X10-2 M-1 min-1 (pH 1.0) to 1.62X10-2 M-1 (pH 10.0) with a maximum value of 12.86X10-2 M-1 min-1 (pH 4.0). Thus thiamine HCl exhibits maximum degradation around pH 4.0 both in the presence and absence of riboflavin

The pH-rate profiles for the photolysis of thiamine alone, and that in the presence of riboflavin have been determined and the behavior of various ionic and nonionic species involved in the reaction have been explained. The profiles follow bell shaped curves with pHmax around 4.0 and may represent two dissociations in the reacting species. Kinetic equations for the reactions of the species involved (protonated thiamine, non-protonated quaternary thiamine, neutral thiamine and thiol thiamine) have been presented

The kinetic data on the photolysis of thiamine HCl alone and that in the present of riboflavin clearly demonstrate that the reaction is inhibited by riboflavin. However, in the presence of divalent phosphate ions, the influence of riboflavin is diminished due to its complexation with phosphate species. The second-order rate constant for this reaction has been determined as 6.24X10-3 M-1 min-1

In water and alcoholic solutions (methanol, ethanol, 1-propanol and 1-butanol) the rate of photolysis of thiamine HCl is dependent upon the solvent dielectric constant and viscosity. An increase in solvent dielectric results in an increase in the rate of photolysis implying the participation of a polar intermediate in the reaction. On the contrary an increase in solvent viscosity leads to a decrease in the rate of photolysis indicating that the reaction is diffusion controlled

The kinetic of UV photolysis of 4-methyl-5-β-hydroxyethylthiazole (a hydrolytic product of thiamine) at pH 1.0-12.0 has also been studied and the pH-rate profile has been prepared indicating that pHmax (2.0) lies near the pKa of thiazoles

Reaction schemes for the photolysis of thiamine HCl in aqueous solutions have been proposed and the role of riboflavin as a photoinhibitor in the reaction has been elucidated

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3052.02 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents 0
170.7 KB
2 1 Introduction 3
106.98 KB
  1.1 Discovery Of Thiamine 3
  1.2 Physico-Chemcial Properties 5
  1.3 Synthesis 6
  1.4 Physiological Functions 7
  1.5 Metabolism 8
  1.6 Pharamacokinetics 8
  1.7 Interrelationship Of Thiamine And Riboflavin In Biological Systems 9
  1.8 Human Requirments 10
  1.9 Thiamine Deficiency And Treatment 10
  1.10 Toxicology And Hypervitaminosis 11
3 2 Degradation Reactions And Stabilization Of Thiamine 13
394.55 KB
  2.1 General Stability 13
  2.2 Oxidation And Reduction 14
  2.3 Hydrolysis 17
  2.4 Thermolysis 24
  2.5 Pyrolysis 82
  2.6 Photolysis 26
  2.7 Radiolysis 33
  2.8 Catalysis 36
  2.9 Biodegradation 38
  2.10 Interactions 38
  2.11 Storage Studies 44
  2.12 Stabilization 47
4 3 Techniques Of Structural And Analytical Studies 53
543.73 KB
  3.1 Chromatographic Techniques 53
  3.2 Spectroscopic Techniques 72
  3.3 Electrochemical Techniques 92
  3.4 Radiometric Techniques 98
  3.5 Chemical Techniques 99
  3.6 Microbiological Techniques 100
  3.7 Object Of The Present Investigation 101
  3.8 Proposed Plan Of Work 103
5 4 Experimental Work 106
168.89 KB
  4.1 Materials 106
  4.2 Methods 109
  4.3 Plan Of Work 122
6 5 Results And Discussion/Photolysis Of Thiamine Hcl Solutions Qualitative Studies 128
135.65 KB
  5.1 Identification Of Thiamine Hcl And Photoproducts 128
  5.2 Spectral Characteristics Of Thiamine Hcl Solutions 137
  5.3 Colour Changes In Photolysed Solutions 144
7 6 Method Development 147
572.53 KB
  6.1 Reversed Phase-High Performance Liquid 147
  6.2 Developing The Separation 147
  6.3 Selection Of Column 150
  6.4 Mobile Phase Optimization 150
  6.5 Validation 154
  6.6 Assay Data 161
8 7 Photolysis Thiamine Hcl Solutions Quantitative Studies 218
866.98 KB
  7.1 Thiamine Hcl Solutions 218
  7.2 Thiamine Hcl And Riboflavin Solutions 254
  7.3 4-Methyl-5-Β-Hydroxyethylthiazole 328
9 8 Conclusions And Suggestions 344
554.62 KB
  8.1 References 349