Folic acid or folacin is found abundantly in green leafy vegetables. The name folic acid comes from the latin root word folium which means leaf. It is very essential for One carbon metabolism and is required for synthesis of certain amino acids, purines and pyrimidines.
Folic acid consists of three components – pteridine ring, p- para amino benzoic acid PABA and glutamic acid. The active form of folic acid is tetra hydro folate THF or FH4. it is synthesized from folic acid by the enzyme dihydrofolate reductase.
Absorption, transportation and storage:
Most of the dietary folic acid is found as poly glutamates which cannot be absorbed by the intestine. Only monoglutamates can be absorbed by the intestine. The enzyme folate conjugase present in the duodenum and jejunum splits the glutamate residues. However inside the cells, tetra hydro folates are found as polyglutamates. As polyglutamate folic acid is stored in liver upto some extent. The body can store 10 – 12 mg of folic acid that will usually last for 2 – 3 months. N5 – methyl tetra hydro folate is abundantly present.
·THF the coenzyme of folic acid is actively involved in One carbon metabolism.
·Many compounds are synthesized in one carbon metabolism with the help of THF.
·Purines are incorporated in to RNA and DNA.
·Glycine and serine are produced
·N – Formyl methionine the initiator of protein biosynthesis is formed
·Choline and ethanolamine are synthesized.
Recommended dietary allowance:
The daily requirement of folic acid is around 200 µg. in the women, higher intake are recommended during pregnancy and lactation.
Folic acid is widely distributed in nature. The rich sources are green leafy vegetables, whole grains, cereals, liver, kidney, yeast and eggs. Milk is poor source of folic acid.
Folic acid deficiency is probably the most common deficiency, observed mostly in the pregnant women. The pregnant women, lactating women, women on oral contraceptives, and alcoholics are also susceptible to folate deficiency. The folic acid deficiency may be due to in adequate dietary intake, defective absorption, use of anti convulsant drugs and increased demand.
Microcytic anaemia may result in folic acid deficiency. Folic acid deficiency in pregnant women may cause neural defects in foetus.
Folic acid antagonists:
Aminopterin and amethopterin are folic acid antagonists.