5-Methyltetrahydrofolate

This chapter will deal with analytical procedures for 5-methyltetrahydrofolate (5MTHF) in cerebrospinal fluid and serum using HPLC coupled to electrochemical and fluorescence detection. 5MTHF is an active one-carbon donor, and it is transported through the blood–brain barrier to serve for a number of essential reactions in the central nervous system including the biosynthesis of thymidylates and purines, methionine synthesis via homocysteine remethylation, the methylation of phospholipids and proteins, the serine and glycine interconversion, and the metabolism of histidine and formate. In this chapter, pre-analytical, analytical, and post-analytical features will be detailed. Briefly, 5MTHF is separated from other folates by reverse phase HPLC and can be quantified with electrochemical or fluorescence detection systems. Adequate sensitivity and selectivity are achieved with both procedures, allowing the detection of profound cerebral folate deficiency, since both systems are capable of detecting very low 5MTHF values in cerebrospinal fluid, lower than 10 nmol/L.