Vitamins of the B Complex

B 13 has been described as a growth factor for rats and for pigs. There is also a description of a vitamin B 14, extracted from urine.

Over the years, there has been a large and controversial literature about what has been called vitamin P. Substances with vitamin P activity are supposed to maintain proper permeability of the blood capillaries of higher animals and to prevent excessive loss of fluid from them. (The letter P is due to this permeability action.) There is now general agreement that substances with P activity are not to be considered as vitamins. At least this is the judicial opinion of the American Society of Biological Chemists.

Para-aminobenzoic acid (often called paba). This relatively simple compound is an important growth factor for many bacteria. As previously noted, it forms part of the folic acid molecule. Para-aminobenzoic acid and sulfanilamide are very close chemically, as is apparent from their structural formulae:

Thus sulfanilamide is an antagonistic analogue of para-aminobenzoic acid, and its antibacterial action is due to this similarity in structure. Choline. This substance, the basic constituent of lecithin, is believed by many to be a vitamin. Rats deprived of choline develop fatty livers and other types of hepatic injury. They may also show degenerative changes in the kidney. Choline deficiency is also a factor in the development of a leg deficiency (perosis) in chicks and turkeys.

It should be remembered that choline is a constituent not only of lecithin, but also of the important humoral substance, acetylcholine. Inositol. Inositol is a derivative of benzene. It can be prepared from hexahydroxy-benzene by reduction, in the course of which 6 hydrogen atoms are added. Thus inositol is hexahydroxy-hexahydro-benzene. It is an optically active substance found in yeast, muscle, and in various other types of animal and plant tissue.

Inositol is important for the growth of yeasts, and is indispensable for some types of yeast. It also promotes the growth of some fungi. In the presence of inositol, chicks grow more rapidly than when it is absent. However, rats may be bred for three generations without inositol, and György was led to conclude that "the facts presented do not, at the present time, warrant the identification of inositol as a primary and really essential vitamin; they rather favor the assumption that it is a supporting and at least not always specific vitamin." a-Lipoic Acid. This substance, also called protogen, is probably to be included among the vitamins of the B group, for it is water soluble. It is important for the growth of some bacteria and for the protozoan Tetrahymena, and it is involved in the oxidation of the important keto acid, pyruvic acid (for this reason it was formerly called pyruvate oxidase factor). Many types of living material contain a-lipoic acid. It is now known to be a derivative of octanoic (caprylic) acid and it contains sulfur in the form of an S-S group.

Throughout the course of vitamin study, there have indeed been many extravagant claims and many false leads. The vast literature is often contradictory and confused. But in spite of this, in the course of time the truth has gradually emerged and the main outlines of the picture are now clear. All sorts of organisms, from bacteria to man, require certain specific types of organic molecules. These can be synthesized by green plants and by many lower organisms. Higher forms have frequently lost the power for such synthesis, and unless, like the ruminants, they provide themselves with huge storehouses for bacteria, they must depend for their existence on obtaining the vitamins with their food.

From the knowledge of the nature of the vitamins, we can begin to develop a chemical anatomy of living systems. The vitamins represent indispensable organic molecules and apparently the same molecules are almost universally needed. Moreover, we are beginning to discover why the vitamins are needed and what work they do in the living cell.

Much of our information is still fragmentary. The vitamin requirements for the lower vertebrates and for the hosts of invertebrate animals have scarcely been investigated at all. Moreover, in some instances we are completely at a loss to account for the fundamental necessity for a given vitamin. Such superficial disturbances as a reddening of the eye or a scaliness of the skin give no direct indication of the part a vitamin may play in protoplasmic activity.