Vitamins are organic compounds of diverse structure which are not used for energy or used into tissue framework but which are required in minute amounts for the normal functioning of living organisms. Animals are unable to synthesize vitamins and must obtain these from diet. They have been defined as “group of organic substances which function catalytically in cellular metabolism” or “as accessory food factors”
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Two of the vitamins required by animals exist as provitamins in plants viz Vitamin A and Vitamin D2. Carotene is converted to Vitamin A by enzymes in the animal lever and ergosterol is converted to Vit. D2 by U.V. light. Vitamins found in plants are divided into two large groups :
A. Fat Soluble Vitamins : Vit. A (Axeropthol), D (Calciferol), E (Tocopherol), K (Phylloquinone).
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B. Water Soluble Vitamins : Vit. B1 or F (Thiamine), Vit. B2 or G (Riboflavin), Vit B3 (Cyanocobalamin), Paraaminobenzoic acid, Vit H (Biotin), Inositol, Folic acid (All of the above mentioned constitute Vit. B complex), Vit. C (Ascorbic acid).