Sayoni Sengupta, Asha Kesari
B.Pharm final year,
Department of Pharmaceutics
Kanak Manjari Institute of Pharmaceutical Sciences
Antioxidants provide an all encompassing protection against cellular wear and damage. Antioxiants occurring naturally are present in all food and herbal medicines. Their addition in small quantities within permissible limits, delay, retard or prevent development of rancidity caused by atmospheric oxygen and thus preserve fats, carotenoids and other nutritive ingredients of food.
Herbal antioxidant in particular is recommended as dietary constituent. Each antioxidant is believed to help address the effect of aging, support healthy brain, maintain capillary integrity and also maintain a healthy cardiovascular system.
REFERENCE ID: PHARMATUTOR-ART-1813
Antioxidant, the word itself is magic suggesting some type of all-encompassing protection against cellular wear and damage. The supply of oxygen is absolutely essential for the existence of higher organisms. As the saying goes too much of even the best is best. Very high concentrations of oxygen are found to be toxic, and can damage tissues. The present day concept of oxygen toxicity is due to the involvement of oxygen free radicals or reactive oxygen species (ROS).
A free radical is defined as a molecule or a molecular species that contains one or more unpaired electrons, and is capable of independent existence.
DEFINITION: An antioxidant maybe widely defined asa molecule capable of slowing or preventing the oxidation of other molecules. Oxidation reactions can produce free radicals which start chain reactions that damage cells. Antioxidants mainly terminate these chain reactions by removing free radical intermediates and inhibit other oxidation reaction by being oxidized themselves. These are widely used as ingredients in dietary supplements in the hope of maintaining health and preventing diseases such as cancer and coronary heart diseases.
SOURCES AND ORIGIN OF ANTIOXIDANTS
Antioxidants are abundant in fruits and vegetables and other foods including nuts, grains and some meats, poultry and fish. Common antioxidants include:
* Green leafy vegetables, including collard green, spinach etc. Rich in b-carotene. beta-carotene is found in many foods that are orange in colour, including sweet potatoes, pumpkins, mangoes etc.
* Lycopene is a potential antioxidant found in tomatoes, watermelons, guava etc.
* Vitamin A is found mainly in three forms:
Retinol (vitamin A), 3, 4-dihydroretinol (vitamin A2) and 3-hydroxy retinol (vitamin A3)
* Vitamin C is also called ascorbic acid and is found in abundance in many fruits and vegetables.
* Vitamin E is also known as alpha-tocopherol and is found in almonds, sunflower, corn and soybean oil etc.
CLASSIFICATIONS OF ANTIOXIDANTS
Antioxidants are mainly classified accordingly:
PRIMARY or NATURAL ANTIOXIDANTS
SECONDARY or SYNTHETIC ANTIOXIDANTS
MECHANISM OF ACTION:
They are chain breaking antioxidant which react with lipid radicals and convert them into more stable products. The antioxidants are mainly phenolic in structures and include the following:
* Antioxidant minerals- These are co-factors of antioxidant enzymes. Example: Selenium, copper, iron, zinc, magnesium.
* Antioxidant vitamin - It is needed for metabolic function. They include Vitamin c, Vitamin e, and Vitamin b.
* Phytochemicals - These are phenolic compounds that are neither vitamins nor minerals. They mainly include the following:
1. FLAVONOIDS - These are phenolic compounds that are widely present in vegetables, fruits, grains, seeds etc.
2. CATECHINS - Most active antioxidant abundantly present in green and black tea and sesamol.
3. HERBS AND SPICE SOURCE - Diterpene, nutmeg, thyme, black pepper, clove, ginger, garlic etc.
These are phenolic compounds that perform the function of capturing free radicals and stopping the chain reaction. Compounds include:
Butylated hydroxylated anisole(BHA)
Butylated hydroxylated toluene(BHT)
Propylgallate (PG) and metal chelating agent(EDTA)
Tertiary butyl hydroquinone(TBHQ)
Broadly antioxidants are classified into five major groups:
1. Primary antioxidants are those compounds namely phenolic substances that terminate the free radical chains in lipid oxidation and functions as electron donors. Example-natural and synthetic tocopherols, alkyl gallates, BHT, BHA, TBHQ etc.
2. Oxygen scavengers, substances that react with oxygen and thus remove it in a closed system. E.g. –ascorbic acid (vitamin c), ascorbyl palmitate, erythorbic acid (isoascorbic acid) etc.
3. Secondary antioxidant, those compounds which function by decomposing the lipid hydroperoxides into stable end products.
4. Enzymatic antioxidant which function by decomposing the lipid hydroperoxides into stable end products.
5. Chelating agents syngerstic substances that enhance the action of phenolic antioxidant. E.g. Citric acid. Amino acid etc.
ADVANTAGES OF NATURAL ANTIOXIDANTS OVER SYNTHETIC ANTIOXIDANTS:
Natural antioxidant (food antioxidant) are structurally phenolic or polyphenolic compounds commonly occurring in plant materials, that interfere with the formation of free radicals, hence prevents the formation of peroxide.
The antioxidants occurring naturally are present in all foods and herbal medicines. Their addition in small quantities , within permissible limits , delay , retard or prevent development of rancidity caused by the atmospheric oxygen and thus preserve fats and oils , carotenoids and other nutritive ingredients of food.
Dietary supplementation of natural antioxidants nutrient such as Vitamin C , A and E and flavonoids to food may prevent many human disease caused by oxidative damage including aging , cataracts , coronary heart diseases , cancer etc.
Synthetic antioxidants are cheap though natural antioxidant are also attractive as additives in food items.
Superiority of Natural Antioxidants over Synthetic ones have been proven in terms of safety, tolerance, and non-toxicity.
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