The identification of the folate conjugates found in rat liver 48 h after the administration of radioactively labelled folate tracers.

About 70% of the radioactivity retained in the livers of rats dosed 48 h earlier with radioactively labelled folate was incorporated into two folate conjugates. The major derivative was purified and isolated by Sephadex G-15, DEAE-cellulose and DEAE-Sephadex ion-exchange column chromatography and paper chromatography. It was identified as 10-formylpteroylpentaglutamate by a combination of spectral, microbiological, chemical and chromatographic techniques. The minor conjugate, though less well characterized, exhibited similar properties and was assigned the structure 10-formylpteroyltetraglutamate. 10-Formylpteroylpentaglutamate (2.0nmol/g) and 10-formylpteroyltetraglutamate (0.25nmol/g) comprised about 20% of the total endogenous hepatic folate as determined by microbiological assay (Lactobacillus casei after conjugase treatment.