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| Pakistan Research Repository | Home |
Title of Thesis |
| Author(s) Izhar Ahmad Ans |
| Institute/University/Department Details University of Karachi/ Department of Pharmaceutical Chemistry |
| Session 2001 |
| Subject Pharmacy |
| Number of Pages 345 |
| Keywords (Extracted from title, table of contents and abstract of thesis) cyanocobalamin, b-vitamins, ascorbic acid , vitamin b12, thiamine hcl, riboflavin, nicotinamide, pyridoxine hcl |
Abstract Cyanocobalamin undergoes photo degradation in the presence and absence of other vitamins to hydroxocobalamin (vitamin B12b) as the main photoproduct which has been identified by thin-layer chromatography and uv-visible spectrophotometry. Cyanocobalamin and hydroxocobalamin have been assayed in photolysed solutions in the presence of other vitamins by a previously reported two-component spectrophotometric method at 525 and 550 nm (pH 4.0) after proper validation. The precision of the assay method lies with +3%. The photolysis of cyanocobalamin at pH 1.0-8.0 in the presence of other B/C vitamins follows first-order kinetics and the apparent first-order rate constants (kobs) indicate a gradual increase with an increase in the concentration of each vitamin The kobs values have been used to calculate the second-order rate constants (k2) for the bimolecular interaction of cyanocobalamin with other vitamins. The variation of k2 for the interaction of cyanocobalamin with other vitamins. The variation of k2 for the interaction of cyanocobalamin at pH 1.0-8.0 with thiamine HCI (5.0 to 1.6 M-1 min-1) riboflavin (5.0 to 1.1 m-1 min-1) NOCOTINAMIDE (6.6 TO 2.2 m-1 MIN-1) PYRIDOXINE hci (5.8 to 1.3 M-1 min-1) and ascorbic acide (2.0 to 1.2 m-1 min-1) indicate that the optimum stability to cyanocobalamin occurs around pH7 The log k2-pH profiles for the photolytic interaction of cyanocobalamin and thiamin HCI/riboflavin/ nicotinamide/ pyridoxine HCI are sigmold shaped curves indicating the increase in rate with a decrease in pH due to gradual protonation of cyanocobalamin (pKa 3.3) and the other vitamin species. Thus the protonated form of cyanocobalamin appears to be more susceptible to photolysis compared to that of the neutral form. The log k-pH profile for the interaction of cyanocobalamin and ascorbic acid represents a combination of two bell shaped curves with minima around pH 4 and 7. This may be explained on the basis of the involvement of nonionised and mononionic species of ascorbic acid (pK 4.1) at pH values below and above 4.1 in the photoreaction as well as their redox characteristics A detailed account of the schemes for the primary (photochemical) and secondary (chemical) reactions involved in the interactions of cyanocobalamin and other vitamins in the pH range studied has been presented and a comparison of cyanocobalamin photo degradation in the presence of individual B/C vitamins has been made |
| Download Full Thesis |  2643.32 KB |
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| S. No. | Chapter | Title of the Chapters | Page | Size (KB) |
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| 1 | 0 | Contents | 101.01 KB |
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| 2 | 1 | Introduction and literature survey | 14 | 342.75 KB |
| 1.1 | Introduction | 14 | ||
| 1.2 | Stability and degradation of cyanocobalamin | 20 | ||
| 1.3 | Methods of analysis of cyanocobalamin | 30 | ||
| 1.4 | Parenteral solutions | 48 | ||
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| 3 | 2 | Object of present investigation | 50 | 28.69 KB |
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| 4 | 3 | Experimnetal | 54 | 217.51 KB |
| 3.1 | Materials | 54 | ||
| 3.2 | Methods | 59 | ||
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| 5 | 4 | Plan of work | 79 | 14.96 KB |
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| 6 | 5 | Results and Discussion, Photolysis of cyanocobalamin solutions-1 qualitative studies and assay method | 83 | 161.63 KB |
| 5.1 | Photochemcial reactions | 83 | ||
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| 7 | 6 | Photolysis of cyanocobalamin solutions-2 kinetics of reaction and rate-pH profiles | 102 | 1183.47 KB |
| 6.1 | Kinetics of cyanocobalamin photolysis | 102 | ||
| 6.2 | Modes of interaction of cyanocobalamin | 221 | ||
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| 8 | 7 | Conclusions and suggestions | 239 | 44.88 KB |
| 7.1 | Conclusions | 239 | ||
| 7.2 | Suggestions | 241 | ||
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| 9 | 8 | Appendix | 244 | 940.96 KB |
| 8.1 | References | 317 | ||
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