IDENTIFICATION OF 10-FORMYLTETRAHYDROFOLATE, TETRAHYDROFOLATE AND 5-METHYLTETRAHYDROFOLATE AS MAJOR REDUCED FOLATE DERIVATIVES IN RAT BILE

Reduced folate derivatives in rat bile were examined using high-performance liquid chromatography with electrochemical detection (HPLC-ED). Three peaks of folate compounds were observed on the chromatograms. From the retention-time profiles and hydrodynamic voltammograms, and the profiles of ultraviolet (UV) absorbance spectra obtained by HPLC with photodiode array detection, these 3 peaks were identified as 10-formyltetrahydrofolate (10-HCO-H4PteGlu), tetrahydrofolate (H4PteG]u) and 5-methyltetrahydrofolate (5-CH3-H4PteGlu). The rates of bile secretion of 10-HCO-H4PteG]u, H4PteG]u and 5-CH3H4PteG]u were 314 +/- 181, 321 +/- 179 and 449 +/- 198 ng/h (mean +/- S.D.), respectively. 10-HCO-H4PteGlu and H4PteGlu together with 5-CH3-H4PteGlu are found to be the major folate derivatives in rat bile. The nonmethylated folates, 10-HCO-H4PteGlu and H4PteGlu, may also play an important role in folate homeostasis.