The relationship of the urinary ascorbate metabolites to specific levels of ascorbate supplementation in the monkey

This study was designed to investigate urinary ascorbic acid (AA) and its metabolites derived from (1-14C) AA administered to trained monkeys fed different levels of ascorbate for extended periods of time. A chromatographic procedure was developed which rapidly separates the urinary compounds into four major fractions with minimal degradation. The distribution of 14C in the four peaks was dependent upon the ascorbate nutritional status of the monkey and remained constant for at least 30 days postlabel. The two major fractions were identified as oxalate and unmetabolized ascorbate. The ascorbate metabolites in the two minor fractions have not been identified. In monkeys maintained on low ascorbate intakes, unmetabolized ascorbate accounted for 10 to 20% and oxalate 25 to 48% of the urinary 14C. The average percentages of 14C in the urine of monkeys fed high levels of ascorbate were 75% for ascorbate and 7% for oxalate. The urine also contained an ascorbate metabolite which degraded during storage and/or chromatography, yielding 14CO2. Ascorbate sulfate was not detected as a urinary metabolite.