INTRODUCTION:

An antioxidant is a molecule capable of slowing or preventing the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons from a substance to an oxidizing agent. Oxidation reactions can produce free radicals, which start chain reactions that damage cells. Antioxidants terminate these chain reactions by removing free radical intermediates, and inhibit other oxidation reactions by being oxidized themselves. As a result, antioxidants are often reducing agents such as thiols, ascorbic acid or polyphenols.¹

Herbal Antioxidant:

Unlike most so-called ‘natural’ antioxidant formulas, Herbal Antioxidant is a concentrated Food and contains the bioflavonoids, amino acids, fiber, and other constituents of high proven anti-oxidant Foods. Food antioxidants, be they vitamins, minerals, or concentrated herbs are superior to the commonly sold non-foods.

Food Nutrient	Compared to USP Vitamin/Mineral Salt
Vitamin C	Over 15.6 times antioxidant effect ⁶
Vitamin E	Up to 4.0 times the free radical scavenging ⁷
Selenium	Nearly 2 times better retained ⁸
Zinc	Better absorption, better form ^9,10

Oxidation process:

Active oxygen species, such as superoxide, ^·OH, ^·OOH, etc., as well as the free radicals derived from the biochemical utilization of oxygen or the prooxidant stimulation of oxygen metabolism, initiate the peroxidation of unsaturated lipids - especially those that constitute bio-membranes -, and are responsible for a large variety of chronic health problems such as aging, cancer, atherosclerosis, cataracts, as well as ischemia-reperfusion disturbances in the brain and heart, kidney and liver damages, inflammatory disorders, gastric ulcer, rheumatism, and the destruction of proteins and nucleic acids, leading to a decrease in cellular activity and to the deterioration of living functions .^2,3

The radical attack operated by an initiator usually follows the following general path- ^4,5

Antioxidant activity by cell:-

The primary mechanism may involve either enzymatic scavenging of oxygenated radicals (such as superoxide dismutases or catalases), or sequestration of iron by proteins (apoferritin or apolactoferrin), or chemical scavengers (such as tocopherols, carotenes or other anti-oxidants).

The second defense mechanism involves the removal of oxidized groups and repair processes¹¹. The mechanism that regulates all these important biochemical processes is not completely known yet, and more work is necessary. Since lipophilic vitamin C-based amphiphiles can penetrate into bio-membranes, some useful information can derive from further studies of their antioxidant activities in supramolecular aggregates that can be viewed as a good tool linking "in vitro" experiments to "in vivo" activities.

Vitamin C:

It in Foods exists in at least two distinguishable forms with accompanying Food factors. Yet, regular ascorbic acid as well as mineral ascorbates are too incomplete to be properly called vitamin C as they do not contain both forms and the accompanying Food factors.Food contains both natural forms of vitamin C ¹².Food vitamin C is also 10x less acidic than ascorbic acid. In vitro studies found that the oxidative reductive potential of Food vitamin C was greater than so-called ‘natural vitamin C with bioflavonoids’ and much greater than isolated ascorbic acid ¹³.

Why is that so important? Because while antioxidants can stop free radical damage, only those substances with proper oxidative reductive potential can actually ‘clean up’ the damage that the free radicals cause! Furthermore, while it is known that diets focused on Foods high in antioxidants can help prevent cancers¹⁴,synthetic antioxidants appear to be so ineffective that they may actually increase cancer risk.¹⁵ So why would anyone want to take the normal ‘antioxidant’ formulas sold instead of Food Herbal Antioxidant which is all Food!

Vitamin C, also called ascorbic acid, helps to maintain healthy collagen in the skin, repair damaged tissue, promote healthy teeth and bones, and boost the immune system.

Vitamin C is one of the more powerful and well-known antioxidants. Just as exposing a cut apple to air causes it to quickly turn brown, cells of the body can also suffer damage when exposed to oxygen, a process known as oxidation. Oxidation causes aging of the skin as well as all other organs and tissues of the body. Vitamin C, as a free-radical fighter, helps ward off wrinkles and many illnesses linked to oxidation, including cataracts, arthritis, heart disease, and cancer.

Role of Vitamin C:-

· It functions as anti-inflammatory, and helps the body fight inflammatory diseases, including arthritis, fibromyalgia, and chronic fatigue.

· It helps the body absorb iron, it is also useful in treating iron deficiency and anemia.

· A multitude of other conditions may be improved vitamin C, including

1) Angina. 12) Rashes.

2) Bronchitis. 13) Rosacea.

3) Bruises. 14) Shingles.

4) Canker sores. 15) Sore throat.

5) Constipation. 16) Sprains.

6) Diabetes. 17) Sunburn.

7) Eyestrain. 18) Yeast infections.

8) Gingivitis. 19) Urinary tract infections.

9) Glaucoma. 20) Scurvy (a disease caused by vitamin 10) Infertility. C deficiency).

11) Joint pain. 21) Hangover.

Vitamin C derivatives as antioxidant agents:-

Triplet excited state carbonyl compounds react with ground state oxygen to give the highly reactive singlet excited molecular oxygen ("singlet oxygen", O₂). Singlet oxygen reacts with proteins, nucleic acids, and cellular lipids, and can therefore damage biological systems¹⁶ .

Triplet state aliphatic carbonyls are formed in biochemical systems by a number of enzymic and non-enzymic mechanisms, such as in lipid peroxidation, and through the actions of peroxidases, and may transfer their energy to suitable aromatic carbonyl, such as duroquinone (DQ). The reduction potential of the DQ/DQ^-. couple is estimated to be about +2.17 V. Other studies have shown that ubiquinone (UQ) is also a powerful oxidant, capable of one-electron oxidation of water.

Triplet carbonyls may produce damage in biological systems either directly, by reaction of the oxidizing triplet state with a suitable cellular target, or indirectly, by acting as sensitizers of singlet oxygen production. Some quinones are recognized as potentially damaging photodynamic photosensitizers in cell and tissue systems. On the other hand, molecules such as Rose Bengal and other uranine's derivatives are being successfully used in cancer therapy.¹⁷

Mechanism as an antioxidant:-

Cellular protection against singlet oxygen damage may be provided by a number of compounds capable of acting as quenchers. The most important physiological quenchers are carotenoids and phenols, notably the tocopherols (E°'=+0.48 V), in particular the reactivity of tocopherol toward peroxyl and phenoxyl radicals decrease in the order alpha>beta=gamma>delta.¹⁸

Ascorbate behaves as a weak singlet oxygen quencher, it is in fact a better one-electron reductant than tocopherol (E°'=+0.23 V), and is supposed to recycle the tocopheroxyl radical in vivo. Its lipophilic derivative 6-O-ascorbyl-palmitate is a good antioxidant in model systems and is also effective in cellular systems. Experiments show that the antioxidant activity of ascorbic acid involves a hydrogen transfer rather than an electron transfer. In vitro, ascorbic acid behaves as an efficient antioxidant in several different ways, for instance by scavenging radicals produced by certain drugs, protecting lung fluids from the damages due to particularly dangerous air pollutants such as O₃ and NO₂^., reducing lipid peroxidation in cigarette smoke, and scavenging peroxyl, thiyl, sulphenyl, urate, nitroxide and other radicals.¹⁹

Tocopherols mainly act as a free radical chain breaking antioxidant in liposomes and cellular membranes, but they also possess reactivity as singlet oxygen quenchers and in repairing free radical damages in proteins. The reducing properties of tocopherols are also matched by ascorbate, however the lipophilic nature of vitamin E provides it with access to lipid sites in membranes and lipoproteins, a level at which ascorbate cannot act. In the case of quinones bearing hydrophobic chains, as ubiquinone, the excited state would be confined to the hydrophobic phase, and the lipidic nature of tocopherols would confer an important advantage.²⁰

Alpha-tocopherol ¹⁸ and melatonin²¹, ascorbic acid is one of the most potent reducing agents for biological systems, but since it reacts with trace metal ions to yield active oxygen species, it may also act as a dangerous prooxidant. ¹⁹,^22,23 It is striking the expression used by Porter to define ascorbic acid as "truly a two-headed Janus, a Dr. Jekyll-Mr. Hyde, an oxymoron of antioxidants".²⁴Furthermore, the cytotoxicity of ascorbic acid is oxygen-dependent and related to its autooxidation process. It is then particularly important to balance of the amounts of vitamin C, vitamin E, and carotenoids in the body, since they play an interesting synergic effect agains lipid peroxidation (see Fig.), i.e. when vitamin E turns into tocopheroxyl radical this reacts with vitamin C that restores tocopherol .^25,26

Vitamin C derivatives as antioxidant agents-

3-alkyl-ascorbic acids, have been tested as antioxidants and found to be very strong chain-breaking agents with a high affinity for biomembranes, suggesting that some lipophilic derivatives of ascorbic acid could be of benefit for protection against reperfusion injury³. Moreover, 3-O-alkyl-ascorbic acids were found to be stable in ointments and to suppress intracellular melanin accumulation in the skin.³The effect of 3-alkyl-ascorbic acids has been reported by Nihro et al^.27

Other studies indicate that 6-O-ascorbyl-alkanoates are much more active in preventing oxidation of linoleic acid than ascorbic acid in SDS, Triton, and CTAB micelles^28,29 despite the fact that ascorbic acid-palmitate and ascorbic acid show a similar efficiency in homogeneous solutions.

The antioxidant synergism of vitamin E and vitamin C has been recognized and extensively studied. The key step is the reaction between the tocopheroxyl radical (TOC^·) and vitamin C (ASC)³⁰:

TOC^· + ASC^- = TOC + ASC

CONCLUSION:-

Vitamin C is a very versatile molecule, in fact it is quite easy to synthesize. Antioxidant activity of vitamin C and of its derivatives is practically the same, the importance of producing large amounts of hydrophobic ascorbic acid-based chemicals is evident, especially for all those cases in which one wants to remove or reduce the damaging effect of radicals such as in certain diseases and in the conservation of food, drugs, or cosmetics, by exploiting the antioxidant activity of the ascorbic acid family.

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Received on 03.11.2009 Modified on 30.11.2009

Research J. Pharm. and Tech. 3(1): Jan.-Mar. 2010; Page 58-61