The term vitamin derives from experiments conducted early in this century, which indicated that proper nutrition was dependent upon introduction of one or several vital nitrogen-containing amines into the diet.
Vitamins are organic molecules (not necessarily amines) that are essential to metabolism in all living organisms. While these molecules serve essentially the same role in all forms of life, higher organisms have lost the ability to synthesize vitamins. There are two major groups of vitamins: the fat-soluble vitamins designated by the letters A, D, E, and K, and the water-soluble vitamins, which are referred to as the vitamin B complex. Most vitamins are converted in vivo into coenzymes that work with metabolic enzymes to complete their biochemical functions. A lack of proper amounts of vitamins in the diet leads to a host of vitamin-deficiency diseases.
Adenine (Vitamin B-4) – Purine that is definitely not a vitamin.
Early studies of chicks and rats that were fed autoclaved cereals without nutritional supplements, indicated that these animals exhibited retarded growth and developed general muscular weakness leading to paralysis. Dr. V. Reader isolated a factor from both yeast and liver that alleviated these symptoms, and he later termed the factor vitamin B-4. This vitamin was determined to be adenine, the purine present as a nucleotide base in both DNA and RNA. However, subsequent investigations indicated that the addition of adenine to the deprived animals' diet did not alleviate the retarded growth and paralysis symptoms. Later, workers found that thiamine (vitamin B-1) cured the symptoms and it is now generally agreed that adenine does not possess any vitamin properties. In fact, the human body has a number of complicated pathways to produce adenine, and this substance is definitely not required as a dietary supplement.