Ascorbic acid vitamin assessment

The DNA adducts, deoxyadenosine and deoxygua-nosine, which are induced by malondialdehyde, the end-product of lipid peroxidation, accumulate in human breast tissues. These adducts are present at relatively higher concentrations in breast cancer cells compared to normal breast cells. In a recent study, serum antioxidative vitamin levels and lipid peroxidation were compared in gastric cancer patients. The level of serum ascorbic acid, a-tocopherol, p-carotene, and retinol were assessed. The levels of ascorbic acid in patients with gastric carcinoma were less than one-fifth of that in the control group, and the production of p-carotene and a-tocopherol were decreased, as well. 

At this time, the selection of the method for determining ascorbic acid content requires some knowledge of the forms of vitamin C likely to be present in a given food product, the number of assays to be performed, and the spectrum of foods being assayed. In addition, the presence of interfering substances must be assessed. 

An intradermal test measures the time required to decolorize a standard dose of 2,6-dichlorophenolindophenol injected into the skin. The accuracy and specificity of the method for diagnosis of ascorbic acid deficiency in animals (C8) and humans (C9) have been considered unsatisfactory. But in a group survey (Rl) the test was reported to be useful as a guide for assessing the level of vitamin C nutrition of the population. 

Vitamin C status can be assessed by measuring plasma levels or urinary excretion. However, due to practical disadvantages, e.g., quantitative sampling of urine and instability of vitamin C, determination of vitamin C in urine has been mainly replaced by determination of plasma levels. Methods include direct determination by FIPLC, or automated assays based on a derivatization of ascorbic acid forming colored or fluorescent derivatives. While a plasma concentration <11.4p.molH is widely used to characterize deficiency, literature data signifying adequate status vary from >17 to 28.4p.moll. ... 

Good linearity was achieved in both ranges of concentrations tested, with correlation coefficients higher than 0.999 in all cases. The proposed method showed a good sensitivity, with limit of detection (LOD) and limit of quantification (LOQ) of 22 and 67 ng/mL, respectively. The method also showed satisfactory precision. All relative standard deviation (RSD) values achieved for peak areas were lower than 4%. The results obtained showed that the applied method has a good reproducibility and that is stable and reliable. The recovery rate of L-ascorbic acid and total vitamin C was evaluated to assess the extraction efficiency of the proposed method and matrix effects. Satisfactory results were obtained for L-ascorbic add (96.6 4.4%) and total vitamin C (103.1 4.8%) [75]. 

Vitamins may be assayed by means of microbial electrodes constructed from cells whose metabolic activity or growth is dependent on the vitamin assayed. Such microbial strains are well known from the commonly used microbiological assays. For instance, the assessment of thiamine was performed by means of yeast cells immobilized in a calcium al inatte membrane. The difference in oxygen consumption before and after incubation with thiamine in the sample is related to the thiamine content [269]. Similar biosensors have been worked out for nicotinic acid (with Lactobacillus arabinosa) [270], nicotine amide (with B. pumilus and E. coli) [271], and L-ascorbic acid (with Enterobacter agglomerans) [272]. 

Ascorbic acid is an important essential nutrient for the health maintenance of the population. Nevertheless, its importance must not be overestimated. The status assessment of the vitamin in well-nourished populations showed only a small percentage of subjects with an insufficient plasma ascorbic acid concentration. It has been documented that risk factors for the development of an ascorbic acid deficiency exist (e.g., smoking, alcohol use, pregnancy, certain pathophysiological conditions). These deficiencies can, however, be overcome without any problems when the current recommendations on vitamin C intake are fulfilled by the intake of either... 

Extrinsic labeling has been used in several studies to assess apparent copper absorption inhumans. This includes studies to evaluate apparent copper absorption from plant- and animal-based diets [263, 264], and also the effect of ascorbic acid [265], age [146, 266, 267], copper intake [267-271], zinc intake [146], and iron supplementation [272] on copper absorption. By measuring urinary excretion of the tracer, copper retention has also been assessed from vitamin B6-defident diets [271], in pregnant women [263], in young men consuming a low copper diet [268], and for high copper intakes [270]. 

A water soluble vitamin which cannot be synthesized by man and therefore has to be obtained from the diet. It is found extensively in vegetables and fruit, especially the citrus varieties. Since the vitamin is carried mainly in the leukocytes, its measurement in these cells gives some indication of the vitamin C status of the body. The ascorbic acid saturation test can also be used to assess the vitamin status. The biochemical role of the vitamin is obscure although it does seem to be required for collagen formation. Deficiency of the vitamin causes scurvy, the symptoms of which can be related to poor collagen formation. These include poor wound-healing, osteoporosis (due to bone matrix deficiency), a tendency to bleed (due to deficiences in the vascular walls) and anaemia. 

A test for assessing the vitamin C status of the body. Ascorbic acid is given orally and its output in the urine is measured. In normal subjects, more of the vitamin will be excreted in the urine, because the tissue stores are already saturated. In deficient patients, less vitamin will be excreted because of its uptake by the tissues. 

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