HPLC analysis of tetrahydrobiopterin and its pteridine derivatives using sequential electrochemical and fluorimetric detection: Application to tetrahydrobiopterin autoxidation and chemical oxidation

► A sensitive direct HPLC method is adapted to measure BH4 and its metabolites. ► The effect of oxidants on BH4 is determined and resulting metabolites measured. ► The primary product of BH4 autoxidation is BH2. ► The primary product of superoxide-catalyzed oxidation of BH4 is BH2. ► Hydroxyl radical driven BH4 oxidation results primarily in dihydroxanthopterin.