The bioavailability of vitamin B₆ in four selected foods (bananas, filberts, soybeans and beef) was determined in five men, aged 22 to 25 years, who were saturated with pyridoxine. The study consisted of a five-day adjustment period followed by a 28-day experimental period. All subjects consumed a constant diet containing 1.34 mg of vitamin B₆ from Monday to Friday of each week, and their self-chosen diets on the weekends. During the experimental period the subjects received 5 mg of pyridoxine each day, including weekends, except on the days when loading doses of crystalline pyridoxine and the selected foods were administered. Doses of 2 mg of crystalline pyridoxine or doses of food containing approximately 2 mg of vitamin B₆ were given. The subjects collected daily 24-hr urine specimens. Vitamin B₆ bioavailability was determined by comparing the yield of 4-pyridoxic acid in response to the test food doses to the yield of 4-pyridoxic acid in response to the 2mg of crystalline pyridoxine. Compared to the 100 percent bioavailability of 2mg crystalline pyridoxine, the mean percent bioavailability of vitamin 65 from banana was 131.4 ± 68.2; from filberts, 88.1 ± 13.9; from soybeans, 58.3 ± 24.3; and from beef, 81.5 ± 28.6. Factors affecting bioavailability of vitamin B₆ from these foods are discussed. / Graduation date: 1983

The purposes of the research presented in this thesis were: (1) to determine the precision with which it is possible to measure changes in vitamin B6 compounds in the blood and urine following oral doses of levels of vitamin B6 (as pyridoxine) which are in the range of the normal daily intake of this vitamin; (2) to compare the effect of three free forms of vitamin B6 (PL, PM, PN) at these same levels using the same assays; and (3) to compare the response of guinea pigs to that of humans when the animals are given three free forms of vitamin B6 at physiological levels. The effect of small incremental doses of pyridoxine (PN) (0.5 - 10 mg) and of equimolar doses of PN, pyridoxamine (PM) and pyridoxal (PL) were studied in five healthy young men. On the day before and during the day of the dose, the subjects were on a controlled diet that supplied 1.6 mg of vitamin B6 each day. During other days of the week, the subjects were on self-selected diets. Timed blood and urine samples were obtained on the day each dose was administered. The parameters measured were: plasma vitamin B6 (PB6), plasma pyridoxal phosphate (PLP), urinary vitamin B6 (UB6) and urinary 4-pyridoxic acid (4PA). Variables reflecting the response to each dose for each of these parameters were calculated in two ways; (1) the percent increase of the maximal post-response value over the pre-response value; and (2) the area under the curve bounded by the values obtained and the times of the samples. For all eight of the variables so calculated, the relationship to the PN doses given were linear in the 0.5 to 10 mg range. Maximal levels of plasma PLP and PB6 were reached at 1/2 hr after the dose for the 0.5, 1, 2, and 4 mg levels of PN. At the 10 mg level, plasma B6 peaked at 1/2 hr for 3 subjects and at 1 hr for 2 subjects. Plasma PLP peaked at 1 hr following the 10 mg PN dose. PB6 was much more responsive to the loading doses than was PLP. The PB6:PLP ratio was maximal at 1/2 hr following the doses. Maximal values of urinary 4PA and UB6 were found in the first 3 hr after the dose. The ratio 4PA:UB6 decreased with increasing PN dose levels and varied for each collection period following the dose. The same variables were calculated for the study of a comparison of 19.44 μmole doses of PN, PM and PL. The PB6 peaks occurred at 1/2 hr for PL and PN, and at 1 hr for PM. The PLP peaks occurred at the following times: PN, 1/2 hr; PM, 3 hr; and PL, 1 hr. Maximal levels of UB6 and 4PA were reached in the first three hr after the dose for all three forms. The percent increase and area variables were able to distinguish between nearly all the responses to the three forms of vitamin B6 administered at the 19.44 μmole level. The PB6 response was largest following the PL dose, but the PLP levels were lower after PL than after either PM or PN. The 4PA values were highest following the PL dose, indicating that the PL dose was metabolized to 4PA rather than converted to plasma PLP. Some of the nutrient contents of the self-selected diets were found to be significantly correlated with some response variables. There was no relationship found between either body weight and 4PA excretion on the day before the dose, or between ascorbic acid intake on the self-selected diets and 4PA excretion on the day before the dose. Strenuous exercise was found to significantly affect plasma PLP levels in subjects who had received the loading doses of PN. In another study, three groups of guinea pigs were each given their Recommended Dietary Allowance of vitamin B6 as PM, PL or PN. The same parameters were measured as for the humans. There were no significant differences between the groups of animals in body weight, organ weights (spleen, liver, kidney, brain), plasma B6 or PLP, or in formed elements of the blood (hemoglobin, hematocrit, white blood cells, red blood cells). Urinary 4PA and UB6 were significantly higher in animals receiving PN. / Graduation date: 1978

Bioavailability (BA) of vitamin B6 (B-6) from foods may be limited. The knowledge of the BA of B6 from food is important in that this would help to understand if the B6 present in the diet of individuals will meet the requirements for this vitamin. The purpose of this study was a) to develop a method to measure the level of glycosylated vitamin B6 (GB6) in the foods; b) to investigate the relative vitamin B6 bioavailability from tuna (T), whole wheat bread (WW), and peanut butter (PB) in humans; c) to follow the excretion pattern of GB6 and relate this to the occurrence of the GB6 in foods. To measure the level of GB6 in foods, the B6 content was determined microbiologically before and after treatment of the foods with β-glycosidase as well as after acid hydrolysis. Animal products contained no measurable amount of GB6, but grain and legumes had 6-75% of total B6 present as GB6. Of the fruits and vegetables analyzed, orange juice (47%) and raw carrots (51%) had the highest GB6 levels. Relative BA of B6 from T, WW, and PB was investigated in eight healthy men in a 52-day study (10-day adjustment and three 14-day experimental periods). B5 intake was set at 1.6 mg/day, with 50% coming from one experimental food and 50% from a basal diet. Urine was analyzed for 4-pyridoxic acid (4PA) and B6; feces for B6; and plasma for pyridoxal-5'-phosphate (PLP). Of these four indices used to assess B6 bioavailability, 4PA and urinary B6 were significantly (p < 0.01) higher in T than in either WW or PB periods. When T was fed, fecal B6 excretion was significantly (p < 0.01) lower than when PB was fed. The B6 in WW and PB was 75% and 63% as available as that from T, respectively. The urine from the last day of each period for five subjects and the last fecal composite for each period was analyzed for the nonconjugated B6 and GB6. The majority of B6 in the feces was in the non-conjugated form. No GB6 was detected in the feces during either the T or PB periods. Only 4% of total B6 in the feces was in the GB6 form when WW was fed. GB6 was found in the urine in all periods. The level of GB6 in the food was inversely related to B6 bioavailability in foods fed to humans in our study and in three other human studies. It appears that the level of GB6 in foods could be used as an index of B6 bioavailability in foods. / Graduation date: 1984

1v. (various pagings) : / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (D.Sc.)--University of Adelaide, Dept. of Organic Chemistry, 1974

4-Pyridoxic acid is the major metabolite of all forms of vitamin B₆ in mammalian species. The determination of 4-pyridoxic acid, therefore, is important in the investigation of vitamin B₆ metabolism and for the establishment of human requirements for the vitamin. Although 4-pyridoxic acid is itself fluorescent, Huff and Perlzweig (1944) developed a classic method for its determination based on the conversion of the metabolite to the even more highly fluorescent lactone. Sarett in 1951 recognized that there are many substances in urine other than 4-pyridoxic acid which are fluorescent and which may interfere with its determination. His attempts to remove the extraneous fluorescent compounds with Decalso or with charcoal were not entirely satisfactory. He proposed, therefore, the administration of a test dose of 4-pyridoxic acid to subjects whose urine was to be analyzed for the metabolite of vitamin B₆, thus rendering the foreign fluorescence less significant by dilution. In 1955, Fujita and associates employed ion exchange chromatography as a means of separating 4-pyridoxic acid from other fluorescent compounds in urine and in 1958 Reddy, Reynolds and Price developed a chromatographic method using Dowex 1 (Cl⁻), a strongly basic anion exchange resin and Dowex 5OW (H⁺), a strongly acidic cation exchange resin for the separation of 4-pyridoxic acid from extraneous fluorescent materials in urine. Eluates from the latter of the two columns, used in sequence, were subjected to a chemical procedure to oxidize the 4-pyridoxic acid to the more highly fluorescent lactone form. The Reddy, Reynolds and Price procedure has provided the means for achieving more valid results than had been possible previously. Because of the importance of this procedure, the dynamics of the ion exchange method of Reddy and associates was investigated. Standards of 4-pyridoxic acid, or 4-pyridoxic acid lactone, and of urine were subjected to ion exchange chromatography using their procedure. Conversion of the 4-pyridoxic acid to the lactone was accomplished by means of the microprocedure of Woodring, Fisher and Storvick (1964). Effluent, wash, and eluate fractions were collected to determine the pattern of elution of the 4-pyridoxic acid, as well as to determine the effect of interfering fluorescence from the resins and from reagents. Eluates of urine from the second in the series of two Dowex ion exchange resins were subjected to paper and thin layer chromatography along with standards of 4-pyridoxic acid and the lactone of 4-pyridoxic acid. Eluates from influents of hydrolyzed urine produced highly fluorescent zones which did not correspond to those of standards of 4-pyridoxic acid or its lactone. A tryptophan load test is often used to diagnose vitamin B₆ deficiency but some of the metabolites of tryptophan are highly fluorescent and may interfere with the fluorometric measurement of 4-pyridoxic acid even after its conversion to the more fluorescent lactone. To study the effect of the presence of tryptophan metabolites on the determination of 4-pyridoxic acid in urine, a test dose of L-tryptophan was administered to one subject and the subsequent 24-hour urine collection was treated according to the chromatographic procedure of Reddy et al. The final eluate was analyzed for 4- pyridoxic acid using the raicroprocedure of Woodring and associates. Readings of fluorescence indicated that much foreign fluorescence remained even after the lactonization procedure. Recovery of 4- pyridoxic acid was 65.5 percent. Therefore, for the determination of 4-pyridoxic acid following a test dose of L-tryptophan, a recovery curve would have to be used for calculation of 4-pyridoxic acid excretion. It was made emphatically clear that there are highly fluorescent compounds present in the resin itself, even after extensive treatment, which cannot be removed. The results of this study emphasize the great importance of maintaining a constant rate of flow, and thus a constant rate of leaching, during chromatography to minimize the effect of the interfering fluorescence. Dowex 5OW (H⁺) will not retain 4-pyridoxic acid well unless the resin has been rendered strongly acidic. It was ascertained that this procedure should be accomplished just before use. 4-Pyridoxic acid and the lactone of 4-pyridoxic acid are eluted almost at once from the Dowex 1 resin but are released in the middle fractions during elution from freshly activated Dowex 50W, with 50 ml. of elutriant. It was determined that chromatography could be undertaken at a relatively rapid flow rate, thus allowing the entire chromatogtaphic procedure and analysis of eluates to be completed in one day. / Graduation date: 1967

Graduation date: 1970

Graduation date: 1978

Graduation date: 1979

Thesis (D.Sc.) -- University of Adelaide, Dept. of Organic Chemistry, 1974.

Thesis (Ph. D.)--University of Wisconsin, 1965. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.