VITAMINS
It is difficult to define vitamins precisely. Vitamins may be regarded as organic compounds required in the diet in small amounts to perform specific biological functions for the normal maintenance of optimum growth and health of the organism. The bacterium E.coli does not require any vitamin, as it can synthesize all of them. It is believed that during the course of evolution, the ability to synthesize vitamins was lost. Hence, the higher organisms have to obtain them from the diet. The vitamins are required in small amounts since their degradation is relatively slow.
History and nomenclature
At the beginning of the 20th century, it was clearly understood that the diets containing purified carbohydrates, protein, fat, and minerals were not adequate to maintain the growth and health of experimental rats, which were natural foods (such as milk) could do. Hopkins coined the term accessory factors to the unknown and essential nutrients present in natural foods. Funk (1913) isolated an active principle (an amine) from rice polishings and, later in yeast, which could cure beriberi in pigeons. He coined the term vitamin (Greek: vita-life) to the accessory factors with a belief that all of them were amines. It was later realized that only a few of them are amines. The term vitamin, however, is continued without the final letter ‘e’. The usage of A, B, and C to vitamins was introduced in 1915 by McCollum and Davis. They first felt there were only two vitamins— fat-soluble A and water-soluble B (anti-beriberi factor). Soon another water-soluble anti-scurvy factor named vitamin C was described. Vitamin A was later found to possess two components[1]one that prevents night blindness (vitamin A) and another anti-ricket factor named vitamin D. A fat-soluble factor called vitamin E, in the absence of which rats failed to reproduce properly, was discovered. Yet another fat-soluble vitamin concerned with coagulation was discovered in the mid-1930s. It was named vitamin K. In the sequence of alphabets it should have been F, but K was preferred to reflect its function (coagulation). As regards the water-soluble factors, vitamin C was identified as a pure substance and named ascorbic acid. Vitamin B was found to be a complex mixture and nomenclature also became complex. B1 was clearly identified as anti-beri[1]beri factor. Many investigators carried out intensive research between 1920 and 1930 and went on naming them as the water-soluble vitamins B2, B3, B4, B5, B6, B7, B8, B9, B10, B11, and B12. Some of them were found to be mixtures of already known vitamins. And for this reason, a few members (numbers!) of the B[1]complex series disappeared from the scene. Except for B1, B2, B6, and B12, names are more commonly used for other B-complex vitamins.
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