Folate is the metabolic active variant of folic acid. Folic acid must be converted to dihydrofolate (DHF), tetrahydrofolate (THF) or methyltetrahydrofolate (mTHF) to exert its vitamin function. Only then it is able to support the de novo synthesis of purines, pyrimidines and amino acids, methylate tRNA, and maintaining haematopoiesis and erythropoiesis (DrugBank Online, 2020-11-06).
Together with riboflavin (vitamin B2), pyridoxine (vitamin B6), and cobalamin (vitamin B12) it regulates homocysteine and cysteine synthesis in a core pathway of methylation (Škovierová et al., 2016). This pathway is also described as "one-carbon metabolism" (McNulty et al., 2019).
Folate deficiency leads to megaloblastic anaemia and can cause an increase of homocysteine which can result in pregnancy complications (McNulty et al., 2019).