Ascorbic acid vitamin structure

Ascorbic acid (vitamin C) is one of the body s endogenous water-soluble antioxidants. Modifications on the ascorbic acid structure have led to some very interesting compounds, such as a novel series of 3-O-alkyl ascorbic-acid derivatives. They have been found to be inhibitors of lipid peroxidation (Nihro etal., 1991). This antioxidant activity is directly related to the lipophilicity of the alkyl chain, su esting that the lipid chain may anchor the antioxidant portion of the molecule in the membrane. 

Ascorbic acid ( Vitamin C ). The crystal structure of this substance cannot be said to be established with the certainty and precision we associate with those already described nevertheless, there is no reason to doubt that the structure suggested by Cox and Goodwin (1936) on the basis of p, limited study of the X-ray reflections is essentially correct. The work is described here because this crystal structure presents some very interesting and instructive features. It is also historically interesting because a preliminary study by optical and X-ray methods played a part in the elucidation of the chemical structure of this biologically important substance. (Cox, 1932 a Cox, Hirst, and Reynolds, 1932 Cox and Hirst, 1933.)... 

Fig. 9.5 Chemical structures of low molecular weight antioxidants Melatonin (a) ascorbic acid (Vitamin C) (b) glutathione (c) lipoic acid (d) a-tocopherol (Vitamin E) (e) and a-tocotrienol (f)...

Monosaccharides with modified structures are often biologically important. Examples include sugar phosphates, deoxy sugars, amino sugars, and ascorbic acid (vitamin C). 

Fig. 7 Structure of ascorbic acid (vitamin C). Oxidation of ascorbic acid to dehydrogenase acid is reversible both forms are biologically active...

As for the ascorbic acid solutions the effect on the dynamical structure of water is different between the isomerism. The effect of L-xylo ascorbic acid (Vitamin C) on the dyiiamical structure of water is less than that of D-arabo ascorbic acid which has little biological activity. It is interesting if this different effect on the dynamical structure of water may relate with a biological activity. 

Although the water-soluble vitamins are structurally diverse, they are put in a general class to distinguish them from the lipid-soluble vitamins. This cla.ss includes the B-complex vitamins and ascorbic acid (vitamin C). The term B-complex vitamins usually refers to thiamine, riboflavin, pyridoxine. nicotinic acid, pantothenic acid, hiotin. cyanocobalamin. and folic acid. Dietary deficiencies of any of the B vitamins commonly are complicated by deftciencies of another mem-ber(s) of the group,. so treatment with B-complex preparations is usually indicated. 

Product stability and performance can be affected by exposure to several oxidative sources, including oxygen, free radicals, UV radiation, oxidative enzymes, catabolic oxidation, and chemical oxidation. Many antioxidants are also good UV absorbers due to their conjugated chemical structure. Typical antioxidants found in cosmetic products are flavonoids, polyphenols, carotenoids, thiols, tocopherol (vitamin E) and ascorbic acid (vitamin C) [71,72], According to Black [73], a combination of antioxidants from different classes is more effective than a single antioxidant due to an antioxidant cascade mechanism. 

Recent studies in biological systems have revealed the presence of a variety of compounds of many structural types that appear to function as antioxidants. The plant kingdom is especially rich in these materials (Larson, 1988). They include flavonoids and other phenolic compounds, alkaloids and other amines, reduced sulfur compounds, uric acid, ascorbic acid. Vitamin E, carotenoids, and many other substances. Often, their principal mechanism of action appears to be the quenching of peroxy radicals, removing them from the autooxidation chain. Vitamin E, for example, reacts with these radicals in a manner entirely analogous to that of BHT ... 

Chart 1. The accepted structural corifiguration of ascorbic acid (vitamin C). an orketolactone with the formula with a molecular weight of... 

The structural formula of L-ascorbic acid (vitamin C) resembles that of a monosaccharide. Humans do not have the enzyme systems required for the synthesis of L-ascorbic acid therefore, for us, it is a vitamin. 

L-Ascorbic acid (vitamin C) resembles a monosaccharide, but its structure has several unusual features. The compound has a five-membered unsaturated lactone ring (review Sec. 10.12) with two hydroxyl groups attached to the doubly bonded carbons. This enediol structure is relatively uncommon. 

Citrus fruits contain citric acid and ascorbic acid (vitamin C). Citric acid is an example of an organic triprotic weakacid.The structure of citric acid is ... 

Top Structural formula of ascorbic acid (vitamin C) note the acidic hydrogen atoms (in color).Boftom Molecular model of ascorbic acid. 

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