Urinary riboflavin metabolites in the rat
Tillotson, J.A.; Karcz, M.S.
Journal of Nutrition 107(7): 1269-1276
1977
ISSN/ISBN: 0022-3166 PMID: 406370 Document Number: 113141
Male rats on a riboflavin-deficient diet for 25 days were given [2-14C]riboflavin to replete their riboflavin pools. During a second depletion period, urine and faeces were collected and 14C excretion was measured. The urine was chromatographed on R-15 resorcinol resin and 14C was measured in all fractions. The 14C compounds in the individual fractions were shown to be different by thin-layer chromatography. The amount of 14C recovered as riboflavin increased after acid hydrolysis of the urine indicating the presence of riboflavin in conjugated forms. All R-15 fractions supported growth in a microbiological (Lactobacillus casei) method of estimating riboflavin, indicating that other derivatives, in addition to riboflavin and flavin nucleotides, are biologically active. The conjugated compounds were apparently less active, as acid hydrolysis of the urine increased its ability to promote growth of L. casei. One 14C metabolite was identified as urea, thus providing evidence for degradation of the riboflavin molecule.