The purposes of this study are (1) to determine the ascorbic acid content of a variety of fruit juices available in Denton, Texas, during March to July, 1943; (2) to ascertain the loss of ascorbic acid when canned grapefruit, orange, pineapple, and apple juices are opened and stored in the home refrigerator for several days' use; and (3) by means of data obtained, to make recommendations as to the most advantageous ways of using one's "points" in purchasing canned fruit juices for their ascorbic acid value.

The purpose of the present study is to determine the ascorbic acid values of orange marmalades made with and without commercial pectin; and to compare these values with those obtained by testing random samples of home and commercial prepared orange marmalades.

A study of the ascorbic acid metabolism of a group of fifty college women in the North Texas State Teachers College between the months of April and July, 1943.

Vitamin C (ascorbic acid) is one of the most essential organic compounds required by the human body for normal metabolic function. Unfortunately, this valuable nutrient is not produced in the human body but most plants and animal can produce this molecule. Although ascorbic acid was not isolated until the early part of the twentieth century, it was known that eating limes and other citrus fruits could ward off the affects of scurvy as early as the 1500's. Ascorbate serves many critical functions in plants as well as the human body. In both, it works as a cofactor in the production of hydroxyproline-rich compounds and helps protect molecules such as proteins, lipids and fatty acids from oxidation. Although the biochemical pathway in animals has been known since the 1950's (Jackel et al., 1950), the exact process by which ascorbic acid is made in plants has eluded scientists. It was shown in 1963 that the inversion of the hexose carbon chain, which occurs in the animal pathway, is not a possible mode of synthesis in plants (Loewus, 1963). As an alternative, a non-inversion pathway was proposed, which achieves ascorbic acid using D-mannose and L-galactose as intermediates, referred to as the Smirnoff-Wheeler pathway (Wheeler et al., 1998). It was shown that transforming lettuce (cv. Grand Rapids and Black Seeded Simpson) and tobacco (cv. Xanthi) with the terminal enzyme in the animal biosynthetic pathway (GLO; L-gulono-gamma-lactone oxidase) increases the ascorbic acid content between 4 and 7 fold. It was also shown through feeding studies that wild type tobacco plants had elevated ascorbate levels when fed the animal precursor (Jain and Nessler, 2000). These data suggest that at least part of the animal pathway could be present in plants, along with the Smirnoff-Wheeler (1998) pathway. To further investigate this discovery, wild type and ascorbic acid-deficient Arabidopsis thaliana were transformed with the glo. Homozygous lines of these transformants were generated and the ascorbic acid levels were compared to the untransformed wild type and mutant plants. Although the wild type plants containing glo did not show a significant increase in ascorbic acid production, all five of the vtc mutant lines had an increased ascorbic acid content relative to wild type level. These data suggest that an alternative pathway is present in plants that does not require many of the steps in the published Smirnoff-Wheeler (1998) pathway to produce ascorbic acid. / Master of Science

Since sweet potatoes, which also furnish vitamin A, are a common food in the popular diets of Texas and are so generally grown over the state, the purpose of this study is (1) to ascertain the amount of vitamin C in eight of the varieties most commonly grown and (2) to determine the effect of the three most popular methods of cooking (boiling, baking, and candying) on the vitamin C content of these varieties of sweet potatoes.

Background: The adequacy of serum ascorbic acid (vitamin C) concentrations in young Canadian adults is unknown. Individuals have varied serum ascorbic acid response to dietary vitamin C, possibly due to genetic variation. Objective: To investigate the prevalence of serum ascorbic acid deficiency in young Canadians and to determine whether common genotypes modify the association between dietary vitamin C and serum ascorbic acid. Methods: Subjects were 1277 men and women aged 20-29 years from the Toronto Nutrigenomics and Health study. Vitamin C intakes were estimated by a 196-item FFQ. Fasting blood was collected to measure serum ascorbic acid by HPLC and to genotype for common polymorphisms in genes that code for glutathione S-transferase (GST) (GSTM1, GSTT1 and GSTP1), haptoglobin (Hp), and vitamin C transporters (SLC23A1 and SLC23A2). Results: 53% of subjects had adequate, 33% had suboptimal and 14% had deficient serum ascorbic acid. Subjects with deficiency had higher mean C-reactive protein, waist circumference, BMI and blood pressure than subjects with adequate serum ascorbic acid. The odds ratio (95% confidence interval) for serum ascorbic acid deficiency was 3.43 (2.14, 5.50) for subjects who did not meet the vitamin C recommendation compared to those who did. The corresponding odds ratios were 2.17 (1.10, 4.28) and 12.28 (4.26, 33.42) for individuals with the GSTT1 functional and null genotypes respectively (interaction p=0.01), and 2.29 (0.96, 5.45) and 4.03 (2.01, 8.09) for the GSTM1 functional and null genotypes (interaction p=0.04). These odds ratios were 4.77 (2.36, 9.65) for the Hp2-2 genotype, but 1.69 (0.80, 3.63) for carriers of the Hp1 allele (interaction p=0.02). Serum ascorbic acid concentrations (mean +/- SE) differed among SLC23A1 rs4257763 genotypes (GG: 24.4 +/- 1.3, GA: 26.8 +/- 1.1, AA: 29.7 +/- 1.4, p=0.002). Conclusions: Serum ascorbic acid deficiency is prevalent and associated with markers of chronic disease. Individuals with GST null or Hp2-2 genotypes had an increased risk of deficiency if they did not meet the recommendation for vitamin C, suggesting that GSTs and haptoglobin may spare ascorbic acid when dietary vitamin C is insufficient, thus protecting against serum ascorbic acid deficiency.

Background: The adequacy of serum ascorbic acid (vitamin C) concentrations in young Canadian adults is unknown. Individuals have varied serum ascorbic acid response to dietary vitamin C, possibly due to genetic variation. Objective: To investigate the prevalence of serum ascorbic acid deficiency in young Canadians and to determine whether common genotypes modify the association between dietary vitamin C and serum ascorbic acid. Methods: Subjects were 1277 men and women aged 20-29 years from the Toronto Nutrigenomics and Health study. Vitamin C intakes were estimated by a 196-item FFQ. Fasting blood was collected to measure serum ascorbic acid by HPLC and to genotype for common polymorphisms in genes that code for glutathione S-transferase (GST) (GSTM1, GSTT1 and GSTP1), haptoglobin (Hp), and vitamin C transporters (SLC23A1 and SLC23A2). Results: 53% of subjects had adequate, 33% had suboptimal and 14% had deficient serum ascorbic acid. Subjects with deficiency had higher mean C-reactive protein, waist circumference, BMI and blood pressure than subjects with adequate serum ascorbic acid. The odds ratio (95% confidence interval) for serum ascorbic acid deficiency was 3.43 (2.14, 5.50) for subjects who did not meet the vitamin C recommendation compared to those who did. The corresponding odds ratios were 2.17 (1.10, 4.28) and 12.28 (4.26, 33.42) for individuals with the GSTT1 functional and null genotypes respectively (interaction p=0.01), and 2.29 (0.96, 5.45) and 4.03 (2.01, 8.09) for the GSTM1 functional and null genotypes (interaction p=0.04). These odds ratios were 4.77 (2.36, 9.65) for the Hp2-2 genotype, but 1.69 (0.80, 3.63) for carriers of the Hp1 allele (interaction p=0.02). Serum ascorbic acid concentrations (mean +/- SE) differed among SLC23A1 rs4257763 genotypes (GG: 24.4 +/- 1.3, GA: 26.8 +/- 1.1, AA: 29.7 +/- 1.4, p=0.002). Conclusions: Serum ascorbic acid deficiency is prevalent and associated with markers of chronic disease. Individuals with GST null or Hp2-2 genotypes had an increased risk of deficiency if they did not meet the recommendation for vitamin C, suggesting that GSTs and haptoglobin may spare ascorbic acid when dietary vitamin C is insufficient, thus protecting against serum ascorbic acid deficiency.

The objective of this dissertation was to study the disposition and absorption of riboflavin and ascorbic acid in healthy male subjects as a function of age. Deficiencies of these vitamins have been found in the elderly and malabsorption is suspected in this population. Absorption of riboflavin was examined by administration of an oral dose of 200 mg of riboflavin-5'-phosphate (FMN) and disposition was studied following a 30 min constant rate IV infusion of FMN equivalent to 25 mg of riboflavin. Ascorbic acid absorption was examined by administration of a 5 g oral dose and disposition was studied following a 1 g IV dose. Test doses of these vitamins were administered to subjects ranging in age from 33 to 85 years. High performance liquid chromatographic assays were developed for the determination of riboflavin and ascorbic acid in plasma and urine. The method for riboflavin separated FMN and flavin adenine dinucleotide under isocratic conditions. Quantification of the three flavins was achieved by fluorescence detection. The assay system for ascrobic acid used a postcolumn reaction for the fluorometric detection of a dehydroascorbic acid derivative. This method used isoascorbic acid as the internal standard. Finally, similar specificity between a "methoxyaniline" colorimetric method and the chromatographic method was observed for the quantification of ascorbic acid in plasma and urine. Albumin plasma concentration and riboflavin protein binding were decreased with age (p < 0.05). The in vitro stability of ascorbic acid in whole blood and plasma decreased with age (p < 0.05, n = 17). The results of this study indicate no age-related alterations in parameters associated with the gastrointestinal absorption of these vitamins. Increased relative renal excretion of riboflavin with age may explain the deficiency of this vitamin. On the other hand, ascorbic acid deficiency with age may be explained by decreased stability of the vitamin in blood.

In controlled release applications a drug is molecularly dispersed in a polymer phase. In the presence of a thermodynamically compatible solvent, swelling occurs and the polymer releases its content to the surrounding medium. The rate of the drug release can be controlled by interfering with the swelling rate of the beads or by influencing diffusion through the viscosity of the polymer. Beads that contain chitosan were prepared through the ionotropic gelation method where tripolyphosphate (TPP) was used as the crosslinking agent. Beads that consisted of 3% w/v isoniazid (lNH) and 5% w/v chitosan were prepared in a 5% w/v TPP solution (pH 8.7) as the primary beads. To improve the drug loading of chitosan isoniazid beads (ClB) the TPP concentration, pH of the TPP solution and the INH concentrations were altered for maximum drug loading. To increase the porosity of the beads of chitosan beads Explotab® (EXPL), Ac-Di-Sol® (ADS) and Vitamin C (VC) were added individually to chitosan solutions at concentrations of 0.1, 0.25 and 0.5% w/v before adding the mixture to the TPP solution. Morphology, swelling and drug loading studies were used to evaluate the different formulations. After these excipients were added individually they were also added in combinations of two excipients respectively and characterised. From the results of the drug loading studies the beads that contained only chitosan and isoniazid showed a percentage drug loading of (43.92%) which is the best of all the beads that were analyzed. The multi excipient combination of Ac-Di-Sol® and Explotab® showed the best swelling capability at both pH levels. Dissolution studies were conducted on all the formu lations over a period of 6 hours (360 minutes) at pH 5.6 and pH 7.4. From the dissolution results it were clear that no chitosan dissolved at both pH values. The dissolution of single pharmaceutical excipient (SPE) and multi pharmaceutical excipient (MPE) formulations can be arranged in the following order: VC/ADS < VC < ADS/EXPL < ADS < VC/EXPL < CIB < EXPL. Explotab® is a potential excipient for enhanced drug release over a wide pH range. / Thesis (M.Sc. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2007.

The most apparent symptom of boron deficiency in higher plants is a cessation of growth. Deficiency causes a reduction in ascorbate concentration and the absorption of nutrient ions. Addition of ascorbate temporarily relieves deficiency symptoms. In boron sufficient plants the addition of ascorbate to media causes an increased uptake of nutrients. In an attempt to discover if ascorbate addition to deficient plants causes increased ion uptake, radish plants were grown hydroponically in four different strengths of boron solution. A colorimetric assay for phosphorus was performed both before and after supplementation. Results, however, were inconclusive.