Urine ascorbic acid

Because of the clinical significance of vitamin C, it is essential to In-able to detect and quantify its presence in various biological materials. Ana lytical methods have been developed to determine the amount of ascorbic acid in foods and in biological fluids such as blood and urine. Ascorbic acid may be assayed by titration with iodine, reaction with 2,4-dinitrophenylhy-drazine, or titration with a redox indicator, 2,6-dichlorophenolindophenol (DCIP) in acid solution. The latter method will be used in this experiment because it is reasonably accurate, rapid, and convenient and can be applied to many different types of samples. 

Trichloroethanoic acid, CCI3COOH. A crystalline solid which rapidly absorbs water vapour m.p. 58°C, b.p. 196-5" C. Manufactured by the action of chlorine on ethanoic acid at 160°C in the presence of red phosphorus, sulphur or iodine. It is decomposed into chloroform and carbon dioxide by boiling water. It is a much stronger acid than either the mono- or the dichloro-acids and has been used to extract alkaloids and ascorbic acid from plant and animal tissues. It is a precipitant for proteins and may be used to test for the presence of albumin in urine. The sodium salt is used as a selective weedkiller. 

Uronic acids are biosynthetic intermediates m various metabolic processes ascorbic acid (vitamin C) for example is biosynthesized by way of glucuronic acid Many metabolic waste products are excreted m the urine as their glucuronate salts... 

Ascorbic acid is very soluble in water and mainly excreted in the urine. No ascorbic acid is excreted during vitamin C deficiency. A minimum amount is lost in the feces, even after intake of gram dosages (154). 

The nurse measures the fluid intake and output, especially when the primary health care provider orders an increase in fluid intake or when a kidney infection is being treated. The primary health care provider may also order daily urinary pH levels when methenamine or nitrofurantoin is administered. These drugs work best in acid urine failure of the urine to remain acidic may require administration of a urinary acidifier, such as ascorbic acid. 

This method requires about 40 g of tobacco which are extracted with ethyl acetate in the presence of ascorbic acid. A trace amount of C-NDELA is added as an internal standard for quantitative analytical work. The filtered extract is concentrated and NDELA is enriched by column chromatography of the concentrate on silica gel. The residues of fractions with p-activity are pooled and redissolved in acetonitrile. Initially, we attempted to separate NDELA on a 3% OV-225 Chromosorb W HP column at 210 C using a GC-TEA system with direct interface similar to the technique developed by Edwards a. for the analysis of NDELA in urine (18). We found this method satisfactory for reference compounds however, it was not useful for an optimal separation of NDELA from the crude concentrate of the tobacco extract (Figure 4). Therefore, we silylated the crude concentrate with BSTFA and an aliquot was analyzed by GC-TEA with direct interface. The chromatographic conditions were 6 ft glass column filled with 3% OV-... 

Since many essential nutrients (e.g., monosaccharides, amino acids, and vitamins) are water-soluble, they have low oil/water partition coefficients, which would suggest poor absorption from the GIT. However, to ensure adequate uptake of these materials from food, the intestine has developed specialized absorption mechanisms that depend on membrane participation and require the compound to have a specific chemical structure. Since these processes are discussed in Chapter 4, we will not dwell on them here. This carrier transport mechanism is illustrated in Fig. 9C. Absorption by a specialized carrier mechanism (from the rat intestine) has been shown to exist for several agents used in cancer chemotherapy (5-fluorouracil and 5-bromouracil) [37,38], which may be considered false nutrients in that their chemical structures are very similar to essential nutrients for which the intestine has a specialized transport mechanism. It would be instructive to examine some studies concerned with riboflavin and ascorbic acid absorption in humans, as these illustrate how one may treat urine data to explore the mechanism of absorption. If a compound is... 

The bone becomes depleted of calcium salts when the urine is acidic over a relatively long period. This was shown by Goto (17) who fed rabbits large doses of hydrochloric acid. He then showed that urinary calcium loss occurred in concert with a marked reduction in mass of the skeletal system, and also that the total non-fat dry weight of bone decreased,implying a loss of bone matrix. A dose-dependent, dietary acid induced loss of labelled calcium from rat bone has been reported by Thorn and his coworkers (18). They demonstrated that in response to graded doses of ascorbic acid, cells in tissue culture, and bones in whole animals fed such doses were depleted of the labelled calcium. 

The determination of 17-ketosteroids is most often determined in the clinical laboratory by the Zimmerman reaction, in which the ether-extracted material is allowed to react with m-nitroaniline to yield a colored product. Thus, any compound with the 17-keto basic structure such as reserpine, morphine, ascorbic acid, or their metabolites will interfere. The Porter-Silber reaction used in the determination of 17,21-dihydroxysteroids is also not specific, and the reaction requires a di-hydroxyacetone side chain. Paraldehyde, chloral hydrate, meprobromate, and potassium iodide have been found to interfere, and patients should be maintained free of these drugs for 24-48 hours before the urine collection (Bll). 

Argenlalion chromalography, 261 Aromatic acids in human urine, 285 Aromatic hydrocarbons, 69 Arylhydroxylamines, 298 Ascorbic acid, 296 Aspirin, 282 Asymmetric diens, 290 Asymmetrical peaks, 58, 82, 160 AIT, stability constants of metal complexes. 278 Atrazine, 292 Atropine, 297 Axial diffusion mobile phase. 8 stationary phase, 8,9 Aza-arenes, 293 Azoxybenzenes, 298... 

Uses Suppress/eluninate bacteriuria associated w/ chronic/recurrent UTI Action Converted to formaldehyde ammonia in acidic urine nonspecific bactericidal action Dose Adults. Hippurate 0.5-1 g bid. Mandelate 1 g qid PO pc hs Peds 6-12 y. Hippurate 25-50 mg/kg/d PO bid. Mandelate 50-75 mg/kg/d PO qid (take w/ food, ascorbic acid w/ adequate hydration) Caution [C, +] Contra Renal insuff, severe hepatic Dz, severe dehydration sulfonamide allergy Disp Tabs SE Rash, GI upset, dysuria, t LFTs EMS Monitor BP for hypovolemia and dehydration OD Sxs unknown symptomatic and supportive... 

Oral absorption of ascorbic acid is via an energy-dependent process that is saturable and dose-dependent. Ascorbic acid is stored in the body. Excessive amounts of consumed vitamin C, i.e. if daily intake surpasses 100 mg, are rapidly excreted in the urine. 

B. Proteus species produce urease (A) that produces ammonia and urea, alkalizing urine. Urine requires acidification for effective therapy. Hippuric (B), mandelic, or ascorbic acids or methionine are urinary acidifying agents. The normal acidic urinary environment is disturbed by recurrent Proteus in-... 

Ascorbic acid may acidify urine, leading to crystalluria. 

Keep urine acidic (pH <5.5) by eating food that acidifies urine (meats, eggs, fish, gelatin products, prunes, plums, cranberries) may need to add ascorbic acid... 

Methenamine mandelate is a salt of mandelic acid and methenamine and both of these possess property of urinary antiseptic. It is rapidly absorbed in gastrointestinal tract and excreted unchanged in urine, where it broken down in acidic pH (< 5) of urine and formaldehyde is released, which inhibits most of the bacteria. It is administered with sodium biphosphate, mandelic acid or ascorbic acid to keep the urinary pH below 6. Its use is restricted to chronic, resistant type of UTI. 

Glucose False negatives may occur when the urine contains small amounts of glucose (75-125 mg/dl) and/or ascorbic acid concentrations of 50 mg/dl or more. Sensitivity may also be decreased by the presence of ketone bodies. 

Vitamins are chemically unrelated organic compounds that cannot be synthesized by humans and, therefore, must must be supplied by the diet. Nine vitamins (folic acid, cobalamin, ascorbic acid, pyridoxine, thiamine, niacin, riboflavin, biotin, and pantothenic acid) are classified as water-soluble, whereas four vitamins (vitamins A, D, K, and E) are termed fat-soluble (Figure 28.1). Vitamins are required to perform specific cellular functions, for example, many of the water-soluble vitamins are precursors of coenzymes for the enzymes of intermediary metabolism. In contrast to the water-soluble vitamins, only one fat soluble vitamin (vitamin K) has a coenzyme function. These vitamins are released, absorbed, and transported with the fat of the diet. They are not readily excreted in the urine, and significant quantities are stored in Die liver and adipose tissue. In fact, consumption of vitamins A and D in exoess of the recommended dietary allowances can lead to accumulation of toxic quantities of these compounds. 

To enhance iron excretion, intensive chelation therapy is used. The most successful drug is desferrioxamine B, a powerful Fe3+-chelator produced by the microbe Streptomyces pilosus,6 The formation constant for the Fe(III) complex, called ferrioxamine B, is 103afi. Used in conjunction with ascorbic acid—vitamin C, a reducing agent that reduces Fe3+ to the more soluble Fe2+— desferrioxamine clears several grams of iron per year from an overloaded patient. The ferrioxamine complex is excreted in the urine. 

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