Ascorbic Add Vitamin C

Whilst these acids are of minor importance in man, another multifunctional acid, ascorbic add (vitamin C 6), has an apparent role in human iron metabolism as one of the postulated factors aiding iron uptake. Ascorbic add reduces Fe111 to Fe" with probable complexation of the latter. It thus converts Fe"1 to a more soluble form. Ascorbic acid can also reduce Cu" to Cu1 (equation 1), and there is accumulating evidence of a link between the metabolism of ascorbic acid and that of Cu.34... 

Rather surprisingly, the average person knows the names of several cofactors and coenzyme precursors, because many of these cannot be synthesized in vivo, and must be supplied in one s diet. This is the reason why a balanced diet should include retinol (vitamin A), ascorbic add (vitamin C), tocopherol (vitamin E), thiamine (vitamin Eh), folic acid etc., as well as zinc and iron. 

Draw all the keto and enol forms of ascorbic add (vitamin C). Why is the one shown the most stable ... 

In Chapter 18, Ebadi discusses the antioxidative properties of the spices capsicum, rosemary, and turmeric, along with the well-known antioxidants that are the tocopherols (vitamin E), P-carotene, and ascorbic add (vitamin C), with the observation that anticancer properties exist. 

Ascorbic add (vitamin C, CgHgOf,) is a water-soluble vitamin. A solution containing 80.5 g of ascorbic acid dissolved in 210 g of water has a density of 1.22 g/mL at 55 °C. Calculate (a) the mass percentage, (b) the mole fraction, (c) the molality,... 

Hydrogenation of L-ascorbic acid (vitamin C) takes place stereoselctively to give l-gluco-1,4-lactone in high yield over Pd-C,156 or better, over Rh-C in water at temperature below 45°C and 0.38 MPa H2 (eq. 3.29).157 It is noted that hydrogen adds preferentially from the least hindered side opposite the side chain. 

Vitamin C (ascorbic acid) is known to inhibit nitrosamine formation. For this reason, manufacturers of cured meat are now required to add vitamin C to their meat products. 

The next step in the catecholamine biosynthesis is side-chain hydroxylation of DA to NE. The enzyme dopamine (3-hydroxylase (DBH) catalyzes this reaction. This enzyme, like TH, is a mixed-function oxidase utilizing molecular 02, in this case to add the OH onto the (3-carbon of the phenelthylamine side chain. DBH is a Cu2+-containing enzyme that, with ascorbic acid (Vitamin C) as a cofactor, carries out the necessary electron transfers. 

The word add comes from the Latin addus, meaning sour or tart, because in water solutions, acids have a sour or tart taste. Lemons, grapefruit, and limes taste sour because they contain citric acid and ascorbic acid (vitamin C). Vinegar is sour because it contains acetic acid. Another common property of acids is their ability to change the color of compounds known as acid-base indicators (Figure 9.1). 

Tasting chemical solutions is not a good practice. However, we have aU had acids such as ascorbic acid (vitamin C), acetylsalicylic acid (aspirin), and citric add (in dtrus fruits) in our mouths, and we are familiar with their characteristic sour taste. Soaps, which are basic, have the characteristic bitter taste of bases. 

The isolation of ascorbic acid was first reported by Albert Szent-Gyorgyi (who called it hexuronie add) in 1928. The structure was determined by ITirst and Haworth in 1933, and, simultaneously, Reichstein reported its synthesis. Haworth and Szent-Gyorgyi, who together suggested that the name be changed to L-ascorbic acid to describe its antiscorbutic (antiscnrvy) activity, were awarded the Nobel Prize in 1937 for their studies of vitamin C. 

Ascorbic acid, HQHt06, also known as vitamin C, is a weak acid. It is an essential vitamin and an antioxidant. A solution of ascorbic add is prepared by dissolving 2.00 g in enough water to make 100.0 mL of solution. The resulting solution has a pH of 2.54. What is Ka for ascorbic acid ... 

A number of inhibitors of carcinogen- and radiation-induced ceU transformation have been identified. These include protease inhibitors (antipain, leupeptin, soybean tryspin inhibitor), vitamin A analogs (retinoids), vitamin C (ascorbic add), glucocorticoids, and lymphotoxins (Kennedy, 1984). 

Failure of high-dose vitamin C (ascorbic add) therapy to benefit patients with advanced cancer. Acontrolled trial. New England Journal of Medicine 301,687-90. 

The term vtiamin C refers to ascorbic acid (the fully reduced form of the vitamin) and to dchydroascorbic acid- Removal of one electron from ascorbic acid yields semidehydroascorbic acid (ascorbate radical). This form of the vitamin is a free radical it contains an unpaired electron- The structures of free radicals are written with large dots. The removal of a second electron yields dehydroascorbic acid. Conversion of ascorbate to dehydroascorbate, via the removal of two electrons, can occur under two conditions (1) with use of ascorbic add by ascorbate-dependent enzymes and (2) with the spontaneous reaction of ascorbate with oxygen. Semidehydroascorbate is an intermediate in this conversion palhway... 

Deficiency in vitamin C, unlike the case with most vitamins, is associated with a specific disease. This disease is scurvy. The symptoms of scurvy include swollen or bleeding gums and hemorrhages under the skin. These symptoms occur when the body s ascorbate is depleted to the point where plasma ascorbate levels are imder 0.2 mg/100 ml. Controlled studies with human subjects revealed that symptoms of the disease may develop within 4 weeks with the consumption of an ascorbate-free diet. Scurvy is rarely encoimtered in developed coimtries, though it may occur in chronic alcoholism. The disease in humans may be prevented by consuming 10 to 15 mg ascorbic add per day. 

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