Dehydro-L-ascorbic acid is usually found in plant tissues in low concentrations and is always associated with ascorbic acid in much higher concentrations. One of the most reliable and direct methods for its estimation is that originally proposed by Roe & Kuether (1943) which is based on the formation of a 2:4-dinitrophenylosazone. Many plant tissues, however, contain so little dehydro-L-ascorbi...

Previous studies have shown that the intact carbon chain of glucose is utilized for the synthesis of L-ascorbic acid in the rat (l-3). Evidence for this precursor relationship came from experiments in which the administration of carbon land carbon 6-labeled glucose tracers resulted in the urinary excretion of n-ascorbic acid labeled predominantly in carbon 6 and carbon 1, respectively. Although...

Detached bean (Phaseolus vulgaris) and strawberry (Fragaria) fruits fed l-gulono-1,4-lactone or l-galactono-1,4-lactone convert this compound, in part, to l-ascorbic acid. When l-galactono-1,4-lactone is given as a 0.25% solution to detached bean shoots, the ascorbic acid content is tripled in less than 10 hours. l-Gulono-1,4-lactone is only 5 to 10% as effective as its epimer. Experiments with...

Dietary administration of 5% L-ascorbic acid plus 3% K2CO3 to male F344 rats clearly enhanced the development of preneoplastic and neoplastic lesions of the urinary bladder initiated with N-butyl-N-(4-hydroxybutyl)nitrosamine. Promotion of carcinogenesis by L-ascorbic acid and K2CO3 was associated with changes in urinary parameters: elevation of pH, increased K+ concentration, and increase in t...

Dopamine, uric acid and ascorbic acid have been determined simultaneously on a poly(3,4-ethylenedioxythiophene) modified electrode using electrochemical techniques. On a bare glassy carbon electrode, all three undergo oxidation and appear as a single peak at around 200 mV, whereas on the modified electrode, distinct peaks with clear potential separation are observed, paving way for their simult...

This study demonstrates a new electrochemical method for rapid determination of ascorbic acid in real samples with electrochemically pretreated screen-printed carbon electrodes. Cyclic voltammetry results indicated that the electrochemically activated electrodes possessed an excellent electrocatalytic activity toward ascorbic acid oxidation and can be successfully used for its selective and sen...

Vitamin C (L-ascorbic acid) is an essential micronutrient that serves as an antioxidant and as a cofactor in many enzymatic reactions. Intestinal absorption and renal reabsorption of the vitamin is mediated by the epithelial apical L-ascorbic acid cotransporter SVCT1 (SLC23A1). We explored the molecular mechanisms of SVCT1-mediated L-ascorbic acid transport using radiotracer and voltage-clamp t...

The effect of ascorbic acid on the monophenolase activity of tyrosinase, using tyrosine as substrate, has been studied. Over the ranges of ascorbic acid concentration used, no direct effect on the enzyme is found. However, a shortening of the characteristic induction period of the hydroxylation reaction is observed. The evolution of the reaction is dependent on the concentration of ascorbic aci...