ascorbic acid

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ascorbic acid:

see vitaminvitamin,
group of organic substances that are required in the diet of humans and animals for normal growth, maintenance of life, and normal reproduction. Vitamins act as catalysts; very often either the vitamins themselves are coenzymes, or they form integral parts of coenzymes.
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Ascorbic acid

A white, crystalline compound, also known as vitamin C. It is highly soluble in water, which is a stronger reducing agent than the hexose sugars, which it resembles chemically. Vitamin C deficiency in humans has been known for centuries as scurvy. The compound has the structural formula shown below.

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The stability of ascorbic acid decreases with increases in temperature and pH. This destruction by oxidation is a serious problem in that a considerable quantity of the vitamin C content of foods is lost during processing, storage, and preparation.

While vitamin C is widespread in plant materials, it is found sparingly in animal tissues. Of all the animals studied, only a few, including humans, require a dietary source of vitamin C. The other species are capable of synthesizing the vitamin in such tissues as liver and kidneys. Some drugs, particularly the terpene-like cyclic ketones, stimulate the production of ascorbic acid by rat tissues.

Vitamin C–deficient animals suffer from defects in their mesenchymal tissues. Their ability to manufacture collagen, dentine, and osteoid, the intercellular cement substances, is impaired. This may be related to a role of ascorbic acid in the forma- tion of hydroxy-proline, an amino acid found in structural proteins, particularly collagen. People with scurvy lose weight and are easily fatigued. Their bones are fragile, and their joints sore and swollen. Their gums are swollen and bloody, and in advanced stages their teeth fall out. They also develop internal and subcutaneous hemorrhages.

There is evidence that vitamin C may play roles in stress reactions, in infectious disease, or in wound healing. Therefore, many nutritionists believe that the human intake of ascorbic acid should be many times more than that intake level which produces deficiency symptoms. The recommended dietary allowances of the Food and Nutrition Board of the National Research Council are 30 mg per day for 1- to 3-month infants, 80 mg per day for growing boys and girls, and 100 mg per day for pregnant and lactating women. These values represent an intake which tends to maintain tissue and plasma concentrations in a range similar to that of other well-nourished species of animals. See Vitamin

McGraw-Hill Concise Encyclopedia of Bioscience. © 2002 by The McGraw-Hill Companies, Inc.

ascorbic acid

[ə′skȯr·bik ′as·əd]
C6H8O6 A white, crystalline, water-soluble vitamin found in many plant materials, especially citrus fruit. Also known as vitamin C.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

ascorbic acid

a white crystalline vitamin present in plants, esp citrus fruits, tomatoes, and green vegetables. A deficiency in the diet of man leads to scurvy. Formula: C6H8O6
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
Along with its neutral salts, L-ascorbic acid is one of the main antioxidants used in plant products to prevent browning and other oxidative reactions in two ways: (1) by acting directly on the enzyme, complexing the copper of the prosthetic group of the polyphenoloxidase, causing its inhibition; and (2) by reducing the quinones to their previous form of phenols, preventing the formation of dark pigments (SAPERS; MILLER, 1998).
As shown for fenoldopam mesylate, L-ascorbic acid has a well-documented effect on reduction of oxidative damage to cells [31, 32].
Compounds 5, 7, 9, and 10 also showed strong scavenging activity with [IC.sub.50] values of 10.58-15.63 [micro]M, compared to the positive control, L-ascorbic acid ([IC.sub.50] = 3.75 [micro]M).
Graphite powder, potassium permanganate (KMn[O.sub.4]), sulphuric acid ([H.sub.2]S[O.sub.4]), phosphoric acid ([H.sub.3]P[O.sub.4]), hydrogen peroxide ([H.sub.2][O.sub.2]), copper sulphate (CuS[O.sub.4]), sodium hydroxide (NaOH), glucose, uric acid (UA), and L-ascorbic acid (AA) were purchased from Sigma-Aldrich.
The chromatograms were recorded at 260 nm using external standards of L-ascorbic acid.
As shown in Table 1, the EtOAc fraction of SHL exhibited potent inhibitory activity against DPPH ([IC.sub.50] value: 63.00 [micro]g/mL) when compared with that of the positive control (L-ascorbic acid, 9.58 [micro]g/mL).
Vitamin C in its primary form of L-ascorbic acid has a proven track record for improving aging skin.
After optimizing the reaction conditions, particularly L-ascorbic acid addition, a 30% improved L-dopa yield was achieved compared to control when the parameters including time of reaction (40 min), L-tyrosine concentration (2.5 mg/ml) and temperature (50C) were optimized by two-factorial Plackett-Burman design (PBD).
The significant decrease in ascorbic acid as a result of drying could be attributed to the high sensitivity of L-ascorbic acid to increase in temperatures above ambient.
'Wear an SPF15 broad spectrum cream to protect against UVA and UVB rays' Skincare that contains vitamin C is also thought to encourage collagen repair (it's usually listed on the label as L-ascorbic acid, ascorbyl palmitate or ascorbyl phosphate).
L-ascorbic acid: a multifunctional molecule supporting plant growth and development.