About Folic Acid Dietary supplement, Folate derivative( B9 ), Water Soluble Vitamin. Mechanism of Action of Folic Acid Folic acid reduced by enzymes folate reductase and dihydrofolate reductase and forms dihydrofolic acid tetrahydrofolic acid respectively. Tetrahydrofolic acid acts as a coenzyme which mediates a number of one carbon transfer reactions by carrying a methyl group as an adduct. It involves a number of reactions such as 1).conversion of homocysteine to methionine. 2).synthesis of thymidylate which is an essential constituent of DNA from methylene-tetrahydrofolic acid. 3). Conversion of serine to glycine by tetrahydrofolic acid and forms methylene-tetrahydrofolic acid. 4).to introduce carbon units at position 2 and 8 during de novo purine synthesis requires formyl-tetrahydrofolic acid and methenyl-tetrahydrofolic acid.5).generation and utilization of "formate pool". 6).For mediating formino group transfer in histidine metabolism.