Abstract

The 13 vitamins are a group of organic substances. Traditionally, they were considered essential, normal constituents of the human diet, required in small amounts, and a participant in normal metabolic processes. Vitamin deficiencies range from well-defined diseases to a variety of vague symptoms. Some vitamins provide the prototypical structure from which medicinal chemists have developed drugs used to treat diseases not associated with a deficiency of that vitamin. Upper dosage levels have been established for those vitamins that can be potentially toxic if taken chronically in excess. Vitamins are traditionally classified into two groups: fat soluble and water soluble. They also can be classified by function: ligand for receptors, cofactors, and antioxidant.