Thesis (Ph. D.)--University of Stellenbosch, 2007. / Includes bibliographical references. Also available via the Internet.

Thesis (M.S.)--Youngstown State University, 2008. / Includes bibliographical references (leaves 79-81). Also available via the World Wide Web in PDF format.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 73-81). Also available on the Internet.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 73-81). Also available on the Internet.

Thesis (M.S.)--Brigham Young University. Dept. of Chemistry and Biochemistry, 2006. / Includes bibliographical references (p. 85-91).

The metabolism of absorbed xenobiotic compounds in humans results in a mixture of target compounds applicable for analysis, trapped in complex biological matrices. Gas chromatography-mass spectrometry (GC-MS) is a powerful analytical technique that has been successfully applied in the analysis of volatile and semi-volatile compounds from complex biological samples. This is due to the ability of GC-MS to separate different sample constituents at trace levels while providing accurate molecular structural information for the resolved compounds. The complexity of biological specimens and their largely aqueous nature, combined with the physicochemical properties of target analytes resulting from metabolism, greatly precludes direct analysis of biosamples by GC-MS. Traditionally, highly laborious and time consuming sample preparation procedures are performed to isolate and chemically alter target analytes to attain suitable amenity for the detection system. Furthermore, routine analytical procedures in clinical toxicology laboratories are signified by short specimen turn-around times. The commonplace use of GC-MS in modern-day laboratories still suffer from prolonged turn-around times that result from both sample preparation steps and lengthy instrumental analysis. Simplified and cost-effective analytical procedures capable of extracting multiple analytes, with divergent functional groups, from biological matrices in a timely manner are therefore required. To address this issue, this work describes the development of validated extractive-derivatization methods combined with fast GC-MS analysis for expedient and accurate quantitation of different analytes in occupational monitoring and workplace drug testing. Extractive alkylation of acidic analytes phenol, o-cresol, mandelic acid, hippuric acid, and (o-, m-, p-) methylhippuric acid for simultaneous urinary bio-monitoring of occupational exposure to benzene, toluene, ethylbenzene, and xylene, respectively, is performed. Extractive acylation for simultaneous urinary confirmation of basic analytes amphetamine, methamphetamine, norephedrine, methcathinone, ephedrine, methylenedioxyamphetamine (MDA), methylenedioxymethamphetamine (MDMA), methylenedioxyethylamphetamine (MDEA) and N-methyl-1-(3,4 methylenedioxyphenyl)-2-butanamine (MBDB) in workplace drug testing is performed. The successful combination of abovementioned techniques alongside fast GC-MS allows increased sample throughput and decreased turn-around time for routine analysis while maintaining bioanalytical quantitative criteria, as required in a clinical toxicology laboratory setting. / Dissertation (MSc)--University of Pretoria, 2009. / Chemical Pathology / unrestricted

by Priscilla Miu-kuen Poon. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1991. / Includes bibliographical references. / ACKNOWLEDGEMENT --- p.1 / ABSTRACT --- p.2 / CONTENTS / Chapter 1. --- INTRODUCTION --- p.4 / Chapter 1.1 --- Discovery of vitamin D / Chapter 1.2 --- Bioavailability of vitamin D and its metabolites / Chapter 1.3 --- Metabolism of vitamin D and its metabolites / Chapter 1.4 --- Mode of action of vitamin D / Chapter 1.5 --- Vitamin D-related diseases / Chapter 2. --- METHODS OF MEASURING VITAMIN D AND ITS METABOLITES --- p.32 / Chapter 2.1 --- Deproteinization / Chapter 2.2 --- Extraction / Chapter 2.3 --- Separation / Chapter 2.4 --- Quantitation / Chapter 3. --- OBJECTIVES --- p.51 / Chapter 4. --- MATERIALS & METHODS --- p.52 / Chapter 4.1 --- Materials / Chapter 4.2 --- General methods / Chapter 4.3 --- Blood collection / Chapter 4.4 --- Radioreceptor assay / Chapter 4.5 --- Serum treatment / Chapter 4.6 --- High Performance Liquid Chromatography (HPLC) / Chapter 4.7 --- Gas Chromatography-Mass Spectrometry (GC-MS) / Chapter 4.8 --- "Serum 1α,25-dihydroxyvitamin D3 analysis" / Chapter 4.9 --- Application of the established GC-MS method / Chapter 4.10 --- Study on hypercalcaemia of tuberculosis / Chapter 5. --- RESULTS --- p.66 / Chapter 5.1 --- Analysis of vitamin D3 standard / Chapter 5.2 --- "Analysis of 1α,25-dihydroxyvitamin D3 standard" / Chapter 5.3 --- Separation of vitamin D3 metabolites / Chapter 5.4 --- "Analysis of lα,25-dihydroxyvitamin D3 in serum samples" / Chapter 5.5 --- Study on hypercalcaemia of tuberculosis / Chapter 6. --- DISCUSSIONS --- p.118 / Chapter 6.1 --- Derivatization / Chapter 6.2 --- Optimization of GC-MS parameters / Chapter 6.3 --- Sample pre-treatment / Chapter 6.4 --- "GC-MS analysis of serum lα,25-dihydroxyvitamin D3" / Chapter 6.5 --- Study on hypercalcaemia of tuberculosis / Chapter 7. --- CONCLUSION --- p.129 / LIST OF ABBREVIATIONS --- p.131 / LIST OF FIGURES --- p.134 / LIST OF TABLES --- p.137 / REFERENCES --- p.139

Thesis (M.Sc. (Nutrition))--North-West University, Potchefstroom Campus, 2007.

Thesis (M. Sc.)(Chemistry)--University of Pretoria, 2005. / Includes summaries in English and Afrikaans. Includes bibliographical references. Available on the Internet via the World Wide Web.

There is a close relationship between the susceptibility to disease and nutritional state, in the sense that an adequate diet enhances resistance to disease. There is an increasing interest in this beneficial relationship among scientists, food manufacturers and consumers. The trend is moving towards functional foods and their specific health benefits. The results of numerous epidemiological studies and recent clinical trials provide consistent evidence that diets rich in fruits and vegetables can reduce the risk of chronic diseases. These protective effects are mediated through multiple groups of beneficial nutrients contained in the fruits and vegetables, one of these being polyphenol antioxidants. The intake of the polyphenols plays an important role in the reduction and prevention of coronary heart disease (CHD), cardiovascular disease and cancer, as a consequence of their associated antioxidant properties. Fruits contain an array of polyphenols with antioxidant capacity. Polyphenols may be classified in two broad groups namely: flavonoids and non-flavonoids. Flavonoid subgroups in fruits are further grouped as catechins, anthocyanins, procyanidins and flavonol among others. Phenolic acids occur as hydroxylated derivatives of benzoic acid and cinnarnic acid, and are classified as non-flavonoids. Polyphenols have redox properties allowing them to act as reducing agents, hydrogen donators and singlet oxygen quenchers, and thus contribute to the antioxidant capacity of fruits and vegetables. Because of the numerous beneficial effects attributed to these antioxidants, there is renewed interest in finding vegetal species with high phenolic content and relevant biological activities. In view of the importance of these substances towards health and food chemistry, this study will focus on the polyphenol and Vitamin C characterisation and quantification of an indigenous South African fruit, the Kei-apple (Dovyalis cafra), thought to have antioxidant properties. Due to the fact that polyphenol content influences the colour, taste and possible health benefits of the fruit / processed food product, this study will supply valuable information to industry in choosing the best fruit processing methods to attain the desired end product. The exploitation of indigenous South African fruits (Marula and Kei-apple) is receiving increasing prominence, not only due to their health benefits, but also the opportunities these present to rural based economics. Furthermore, this research will serve as a platform for further research on the Kei-apple and other indigenous South African fruits with possible health benefits. Aims: The overall aim of this study is the quantification and characterisation of various nutritionally important antioxidants (polyphenols and ascorbate) in the Kei-apple fruit in its entirety, as well as in its individual fruit components (peel, flesh and seeds). In addition, the total antioxidant capacity of the entire fruit and the various fruit components will be determined in the unfractionated and fractionated fruit extracts. Gas chromatography coupled mass spectrometry (GC-MS) characterisation of the individual polyphenol components will also be analyzed in order to speculate on possible specific health benefits which the Kei-apple may possess. Methods: The study was designed to ensure that a representative fruit sample was collected. Approximately 100 kg Kei-apples were picked in the month of November 2004 from the Bloemhof area in South Africa. A sample of 50 fruits was rinsed and separated into the various components (peel, flesh and seeds). An additional 50 fruits were randomly selected, cleaned and used in their entirety for data representative of the entire fruit. The sample extracts were prepared, after being grounded and lyophilized, by a method described by Eihkonen et al. (1999) using 70% aqueous acetone. The C18-fractionation on the fruit and separated fruit components resulted in four fractions containing (1) phenolic acids; (2) procyanidins, catechins and anthocyanin monomers; (3) flavonols and (4) anthocyanin polymers. The total polyphenol content of the fruit and fruit components as well as the above mentioned C18-fractions were determined by Folin-Ciocalteu's method (Singleton & Rossi, 1965). Both free and total ascorbate concentrations in these samples were determined as described by Beutler (1984), in addition to total sugar content of these via standard methods. Apart from their nutritional interest, both these measurements are necessary for the correction of the total polyphenol concentrations. The total antioxidant capacity of the entire fruit and various fruit components was determined by measuring the oxygen radical absorbance capacity (ORAC) and ferric reducing antioxidant power (FRAP) of the unfractionated and fractionated extracts. Using GC-MS analysis, the various individual polyhenol compounds contributing to the total polyphenol content of the Kei-apple was separated, identified and quantified. This quantitative data was captured and statistically analysed. The analysis of variation was performed using the Tukey Honest Significant Difference test for post-hoc comparison. ORAC, FRAP and polyphenol Pearson correlation analyses were performed using Statistics (Statsoft Inc., Tulsa, Oklahoma, USA) with significance set at P ≤ 0.05. Results and discussion: This study determined the presence of various nutritionally important antioxidants (polyphenols and ascorbate), the total antioxidant capacity in the entire fruit as well as in the individual fruit components (peel, flesh and seeds) and their polyphenol sub group fractions. Total phenol content: The Kei-apple, in its entirety, has a polyphenol concentration of 943 ± 20.3 mg GAE/100g dry weight. Comparison of the individual fruit components showed the seeds to have the highest total polyphenol concentration with 1990 ± 31.3 mg GAE/100g dry weight, followed by that of the peel, 1126 ± 45.8 mg GAE/100g dry weight and then that of the flesh, 521 ± 1.01 mg GAE/100g dry weight. Total, L-ascorbic (ASC) and L-dehydroascobic (DHA) concentration: The total ascorbate of Kei-apple fruit is 517 ± 0.92 mg/100g dry weight. In contrast to the polyphenol content, the flesh of the Kei-apple had significantly the highest concentration of total ascorbate 778 ± 1.20 mg/100g dry weight, Gascorbic 241 ± 21.0 mg/100g dry weight, as well as Gdehydroascobic 537 ± 22.2 mg/100g dry weight. The ratio of Lascorbic acidltotal ascorbate for the flesh, entire fruit, peel and seed is 0.31,0.43,0.49,0.95, respectively, indicating the seeds are the most stable source of biologically active Vitamin C, with 95% of the total ascorbate occurring as G ascorbate. This is also in line with the total polyphenol content of these components, confirming a polyphenol sparing effect on ascorbate. C18-fractionation extracts: Solid phase (C18) fractionation of the Kei-apple fruit and fruit components showed that the fruit, peels and seeds consist predominantly of phenolic acids, followed by procyanidin, catechin and anthocyanin monomers and thereafter varying amounts of anthocyanin polymers and flavonols. Antioxidant capacity: The antioxidant capacity of the entire fruit and individual fruit components as determined by ORAC, (r=0.76) and FRAP, (r=0.95) significantly correlated with the total polyphenol content, as well as to each other (r=0.88), indicating both to be good predictors of antioxidant capacity. GC-MS polyphenol characterisation of the Kei-apple: Caffeic acid and hydro-p-coumaric acid were seen to be the phenolic acids occurring in the highest concentrations in the Kei-apple fruit. The majority of these are concentrated in the flesh and in the case of caffeic acid, also in the peel. The order of predominance of other major non-flavonoid components in the whole fruit analysis are m-hydroxybenzoic acid > p-hydroxyphenyl acetic acid > 3-methoxy-4- hydroxyphenylpropionic acid > p-coumaric acid. The peel of the Kei-apple, apart from caffeic acid, has exceptionally high concentrations of ferulic acid and also serves as a source of protocatechuic acid. Syringic acid was most prominent in the seeds. Although the total flavonoid concentration in the Kei-apple was low, taxifolin and catechin were identified and the seeds almost entirely accounting for these. Conclusion: From this study it was concluded the Kei-apple is a rich source of antioxidant compounds (polyphenols and ascorbate), with a strong antioxidant capacity, and hence may be associated with health promotion properties, particularly in the prevention of cancer, cardiovascular disease, and neurodegeneration. Additionally, due to the increased scientific and commercial interest in this fruit, it is essential to take into consideration the various factors (agronomic, genomic, pre- and post harvest condition and processing) and tissues. This might affect the chemical composition of the final marketed product, which may play a significant role in determining the polyphenol and ascorbate composition and bioactivity of these compounds during food processing procedures. Hence, the polyphenol composition of the various fruit components should be taken into consideration when selecting a method of fruit processing into the desired end product. / Thesis (M.Sc. (Nutrition))--North-West University, Potchefstroom Campus, 2007.