Folic acid

This vitamin occurs in green leaves; hence the name, which is taken from the Latin word for leaf. Folic acid also occurs in mushrooms and yeast; and in animal tissues, such as liver and kidney. The vitamin has been called by many different names, and it exists in various forms. These have different potencies for different types of organisms.

Chemically, folic acid consists of pteroic acid combined with the common amino acid, glutamic acid. Pteroic acid itself is a combination of para-aminobenzoic acid and a pteridine base. Pteridine bases are pyrimidine derivatives related to the pyrimidine bases thymine and uracil found in the nucleic acids. The formula of folic acid is given below:

The compound shown above is pteroylglutamic acid, sometimes called PGA. Pteroic acid may also combine with 3 glutamic acid groups to form pteroyltriglutarnic acid (P3GA) or with 7 molecules of glutamic acid to form pteroylheptaglutamic acid (P7GA). All of these compounds are found naturally and all have vitamin activity for certain types of living materials.

Folic acid is required by some bacteria, by certain ciliate protozoal, by some insects and by various birds and mammals. The bacteria in the rat intestine normally manufacture a sufficient quantity of the vitamin, and treatment with antibiotics such as sulfa drugs is necessary to cause folic acid deficiency. Folic acid is commonly an essential growth factor, not only for bacteria but for higher organisms as well. Lack of the vitamin in mammals results in various ailments, but especially in a type of anemia characterized by a small number of red blood cells of large size. This type of anemia, called macrocytic anemia, occurs in the tropical disease sprue, and sprue can be cured either by liver extract (which contains folic acid) or by folic acid itself. Folic acid is apparently important both for growth and cell division. When chick embryos are in contact with antagonistic analogues such as 4amino folic acid, their growth is greatly retarded. Similar results have been obtained in numerous other studies with folic acid antagonists. Thus 4-amino folic acid has a retarding effect on tumor growth.

A substance related to folic acid is the so-called "citrovorum factor," 45 which is apparently identical with "folinic acid." This factor favors growth of the bacterium, Leuconostoc citrovorum. The citrovorum factor may be obtained from liver extracts; also it is excreted into the urine of rats or men fed folic acid.