Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.)--University of Hawaii at Manoa, 1994. / Includes bibliographical references (leaves 157-168). / Microfiche. / xxi, 168 leaves, bound ill. 29 cm

The main objective of this research is to investigate aspects responsible for the dynamics of guest molecules complexed with cyclodextrins (CD)s). We have shown with the use of a variety of photophysical techniques that the complexation. dynamics for guests with CDs are dependent on the structure of the guest molecule. An assortment of photophysical methods that included steady-state fluorescence, UV-Vis absorption, and laser-induced optoacoustic (LIOAS) spectroscopies, in combination with time-resolved techniques such as single photon counting fluorescence and triplet-triplet absorption (T-T abs) spectroscopies were employed to obtain a detailed understanding of the photophysics for fluorenones. From these photophysical investigations, we have demonstrated that several effects such as the nature and position of substituents, and the properties of the microenvironment are responsible for the photophysics observed for these aromatic ketones. The complexation of fluorenone and xanthone with CDs was investigated to obtain more information on how the structure of the guest molecule can affect the complexation dynamics of these host-guest systems. Induced circular dichroism (ICD) and picosecond fluorescence spectroscopy were employed to detail the structural differences observed for the CD complexes of these two ketones. Equilibrium constants were observed to be larger for xanthone with β-CD than with fluorenone. This result suggested that a more favorable complex is formed for xanthone than for fluorenone. However, in the presence of α-CD, fluorenone formed 2:1 host-guest complexes that were not observed for xanthone. These photophysical studies with additional support from theoretical calculations provided useful tools for understanding the structural intricacies of CD host-guest systems. These types of studies will be invaluable to the understanding of dynamics within supramolecular systems. To expand our knowledge on the structure-dynamics relationship that exists for CD complexes, we investigated the complexation dynamics of charged probes with CDs. Two styrene derivatives, trans-anethole (t-Ane) and 4-vinylanisole (4-VA), were chosen as precursors for the radical cations examined in these investigations. Quenching studies have demonstrated that the exit of the radical cations of t-Ane and 4-VA complexed with CD, even in the presence of alcohols, was faster than 20 ns. In addition, complexes with 2:1 host-guest stoichiometries were unsuccessful in reducing the dissociation rate constant of these charged species. From these studies we have shown that a structure-dynamics relationship does exist for CD host-guest systems. With the use of a variety of photophysical techniques and theoretical calculations, we have been able to better evaluate how the photophysics of probe molecules can be explored in the study of host-guest complexation. Small changes in structure have important consequences on the binding efficiencies of these probes to CDs. This information will aid in the understanding of the structure-dynamics relationship that occurs in supramolecular systems. / Graduate

Nifedipine is a photolabile calcium channel antagonist which undergoes rapid photodegradation in solution and in solid-state with an accompanying loss of pharmacological potency and clinical efficacy. Nifedipine photostabilization which has received considerable attention has principally been achieved by physical obscuration and through the use of colourants or ultraviolet light absorbers incorporated into liquid preparations, translucent packaging materials, gelatin capsules and/or their fillings and tablet coatings or cores. This study was initiated by a South African pharmaceutical manufacturer in response to increasing evidence that cyclodextrin (CD) inclusion complexation may improve drug photostability. The brief was to evaluate the potential of selected cyclodextrins as photoprotecting agents for nifedipine in the solid-state. Areas of investigation included i) quantitative method development and validation for selective determination of nifedipine, ii) phase solubility studies to establish the solubilizing potential and complexing tendencies of selected cyclodextrins, iii) preparation of solid-state nifedipine - cyclodextrin binary systems using an industrially applicable method, iv) pre-formulation photostability studies to determine the effects of the cyclodextrins on solid-state nifedipine photostability and v) comparative in vitro dissolution assessments of nifedipine, the nifedipine - cyclodextrin binary systems and their respective physical mixtures. Phase solubility studies demonstrated that soluble nifedipine - cyclodextrin complexes were formed in aqueous solution, but the magnitude of the interactions were generally low as reflected by the calculated stability constants which decreased in the rank order, heptakis (2,6-dimethyI)-β-CD (DM-β-CD) > randomly methylated-β-CD (RM-β-CD) > β-CD ≈ 2-hydroxypropyl-β-CD (2HP-β- CD) > γ-CD ≥ 2-hydroxypropyl-γ-CD (2HP-γ-CD). An industrially applicable kneading method yielded binary systems with spectral and thermal characteristics similar to the respective physical mixtures, implying weak solid-state inclusion complexation. Preparation of an amorphous nifedipine - RM-β-CD product using a heating method is reported. A 1.7- and 1.9-fold improvement in solid-state nifedipine photostability was observed for I : 1 molar ratio β-CD and γ-CD kneaded products, respectively, when exposed to window-filtered daylight and could be attributed to changes in opacity of the crystalline kneaded products. The remaining cyclodextrins produced negligible nifedipine photostabilization. Nifedipine in vitro dissolution was improved considerably from γ-CD and RM-β-CD .kneaded products as a result of increased nifedipine wettability, solubility and reduced particle size. iii

published_or_final_version / abstract / Botany / Doctoral / Doctor of Philosophy

No description available.

Thesis presented in partial fulfilment of the requirements for the degree of Master of Technology (Food Technology) Department of Food Technology Faculty of Applied Sciences 2014 / The aim of this study was to evaluate the effect of transglutaminase (TG) and cyclodextrinase (CG) on the rheological characteristics of oat dough and shelf-life characteristics of oat bread with a view to developing oat bread with improved texture and shelf-life. Firstly, the effects of yeast, carboxylmethylcellulose (CMC), plain yoghurt (YG), transglutaminase (TG) and cyclodextrinase (CG) on the mixing, pasting, thermal, quantification of free amino acid groups and protein crosslinking properties of oat dough were investigated through a 25-2 fractional factorial design resolution III with yeast (1.25, 3.25%), CMC (1, 2%), YG (10.75, 33.75%), TG (0.5, 1.5%) and CG (10, 40 μl) as independent variables. Among all the ingredients, only CMC, YG, and TG exhibited significant (p < 0.05) effects on the mixing properties of oat dough while yeast and CG slightly affected it. TG addition increased water absorption (34.80 - 38.45%) and peak resistance (696.40 - 840.30 FU) but decreased the dough softening (93.20 - 67.75 FU) as its level varied from 0.5 to 1.5 g. CG did not significantly (p > 0.05) affect the mixing properties of oat dough. As its level increased from 10 - 40 μl, the water absorption (38.45 - 34.80%), energy at peak (11.45 - 3.75 Wh/kg), peak resistance (840.30 - 696.40 FU) slightly decreased while the softening of oat dough increased from 67.75 to 93.20 FU. The addition of yeast and YG showed significant (p < 0.05) impacts on the pasting properties of oat dough compared to CMC, TG and CG. The storage modulus of oat dough was slightly (p > 0.05) increased by adding TG (180.37 - 202.78 kPa) and CG (170.75 - 175.71 kPa). TG decreased the loss modulus (65.95 - 62.87 kPa) of oat dough while CG increased it from 62.01 - 64.61 kPa. The thermal properties of oat dough were slightly affected by all the ingredients. The denaturation temperature was increased by incorporation of TG (6.53 - 8.33°C) and CG (6.42 - 8.33°C) but there was a decrease of enthalpy due to addition of TG (from 0.76 to –4.05 J/g) and CG (1.11 to –4.05 J/g). Only CG decreased the number of free amino acid groups (0.94 - 0.62) confirming that it catalysed the protein crosslinking of the oat glutelin while other ingredients increased it. Secondly, as CMC, YG and TG affected the mixing, pasting and thermal properties of oat dough, oat bread was baked with carboxylmethylcellulose (CMC), yoghurt (YG) and transglutaminase (TG) following a 33 Box-Behnken design consisting of CMC (1, 2 g), YG (10.75, 33.75 g) and TG (0.5, 1.5 g) as independent variables. The physical and textural analysis of oat bread showed that CMC, YG and TG addition did affect oat bread. TG decreased the springiness (6.47 - 4.14 mm), specific volume (1.61 - 1.54 ml/g) and increased hardness (537.85 - 692.41 N) of oat bread. No significant effect was observed on the colour parameters of crust and crumb of oat bread. Despite the optimal oat bread exhibited a high desirability, its high hardness and low springiness remain some challenges associated with oat bread production. Since it was well established that TG increased hardness and decreased springiness of the optimal oat bread, improvement was needed for the production of best oat bread. Thirdly, Psyllium husks (PH) and cyclodextrinase (CG) were added in five (05) best oat bread formulations such as (1) PH + CG, (2) CG, (3) TG + CG, (4) TG + PH and (5) TG + PH + CG. The best oat bread formulation with low hardness containing PH and CG was further used for sensory and shelf-life studies. The combination of ingredients psyllium husks and cyclodextrinase significantly (p < 0.05) improved the textural properties of best oat bread. It decreased the hardness (94.88 N) and increased the springiness (10.97 mm) of the best oat bread. Fourthly, the sensory evaluation showed that the consumers highly appreciated the crumb colour and texture of the best oat bread than the ones of wheat bread. In addition, they found that there was a strong correlation in crust and crumb colour between wheat and the best oat bread. However, some differences existed between the wheat and best oat bread. The best oat bread exhibited a less preference in taste than its wheat counterpart. The best oat bread positively received an overall acceptability (4.07) as wheat bread (4.22). Fively, the shelf-life studies of the best oat bread revealed that the pH and TVC of the best oat bread were more affected by the time, temperature and the interaction of both parameters (time and temperature) than Total Titratable Acidity (TTA), yeasts and mould as the storage time passed. The best oat bread could safely be stored up to 21 days at refrigeration temperature (5°C) with a Total Viable Count (TVC) load of 105 cfu/g. Finally, using survival analysis for the shelf-life studies of the best oat bread, the mathematical model revealed that the risk of deteriorating increased with the temperature.

Liu Ho Yan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references. / Abstracts in English and Chinese. / Abstract (Chinese) --- p.ii / Abstract --- p.iii / Acknowledgement --- p.iv / List of Tables --- p.v / List of Figures --- p.vi / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Overview and history --- p.1 / Chapter 1.2 --- Structure of β-cyclodextrin --- p.2 / Chapter 1.3 --- Complexation with aromatic compounds --- p.2 / Chapter 1.4 --- Scope of the thesis --- p.6 / Chapter 1.5 --- References --- p.8 / Chapter Chapter 2 --- Synthesis and characterization of β-cyclodextrin epichlorohydrin copolymer --- p.10 / Chapter 2.1 --- Introduction --- p.10 / Chapter 2.2 --- Effects of major parameters on polymerization --- p.11 / Chapter 2.3 --- Polymerization mechanisms --- p.13 / Chapter 2.4 --- Synthesis and characterization of β-cyclodextrin epichlorohydrin copolymer --- p.13 / Chapter 2.5 --- References --- p.18 / Chapter Chapter 3 --- β-Cyclodextrin epichlorohydrin copolymer as a solid-phase extraction sorbent for aromatic compounds --- p.19 / Chapter 3.1 --- Introduction --- p.19 / Chapter 3.2 --- Experimental --- p.22 / Chapter 3.3 --- Results and discussion --- p.25 / Chapter 3.3.1 --- Effect of pH on the extraction of aromatic compounds --- p.25 / Chapter 3.3.2 --- Optimum stirring time for the extraction of aromatic compounds --- p.28 / Chapter 3.3.3 --- Recoveries of aromatic compounds --- p.28 / Chapter 3.3.4 --- Analysis of synthetic standard sample --- p.30 / Chapter 3.4 --- Conclusions --- p.33 / Chapter 3.5 --- References --- p.33 / Chapter Chapter 4 --- Simultaneous determination of Ni(II) and Cu(II) in tea sample by EDXRF after preconcentration with 4-(2-pyridylazo)resorcinol-included β-cyclodextrin epichlorohydrin copolymer --- p.40 / Chapter 4.1 --- Introduction --- p.40 / Chapter 4.2 --- Experimental --- p.41 / Chapter 4.3 --- Results and discussion --- p.45 / Chapter 4.3.1 --- Optimum pH for the inclusion of PAR in β-CDEP cavity --- p.45 / Chapter 4.3.2 --- Saturation time for the inclusion of PAR in β-CDEP cavity --- p.45 / Chapter 4.3.3 --- Optimum pH for the reaction between PAR and metal ions --- p.47 / Chapter 4.3.4 --- Calibration curves and detection limits of Ni(II) and Cu(II) --- p.47 / Chapter 4.3.5 --- Analysis of synthetic standard sample --- p.50 / Chapter 4.3.6 --- Analysis of tea sample --- p.50 / Chapter 4.4 --- Conclusions --- p.53 / Chapter 4.5 --- References --- p.53 / Chapter Chapter 5 --- Conclusions --- p.55

Copies of author's previously published works inserted. / Includes bibliographic references. / 154 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Studies the chiral recognition of carboxylic acids and amino acids by cyclodextrins and metallocyclodextrins. / Thesis (Ph.D.)--University of Adelaide, Dept. of Chemistry, 1994?

"July 2004" / Includes copies of publications by the author as appendix. / Includes bibliographical references. / ix, 181, [26] leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Describes the construction and characterisation of a variety of supramolecular architectures based on cyclodextrins. / Thesis (Ph.D.)--University of Adelaide, School of Chemistry and Physics, Discipline of Chemistry, 2005?