Clarification and Quantitation of Primary (Tissue) and Secondary (Microbial) Catabolites of Riboflavin That Are Excreted in Mammalian (Rat) Urine

Abstract

Riboflavin derivatives were quantitated and identified in urine of rats fed 0, 2 and 6 micrograms riboflavin/g diet per day both with and without added succinyl sulfathiazole for 6 wk. Two rats from each dietary group were placed in metabolic cages and urine was collected in the dark for 24 h. On the fourth week, a third animal from each group received an i.p. injection of [2-14C]riboflavin before being placed in a metabolic cage and urine collected in the dark for 48 h. Urine samples were extracted with phenol for flavin components and with chloroform for lumichrome and derivatives. Riboflavin was the predominant flavin excreted by rats in all dietary groups, followed by hydroxymethylriboflavins and smaller amounts of flavin mononucleotide (FMN), lumiflavin and 10-hydroxyethylflavin. Carboxylumichromes accounted for 5-10% of the total flavin-derived fluorescence in urine of rats fed 2 and 6 micrograms riboflavin/g diet and were reduced to approximately 3% when sulfathiazole was added to the base diets. Carboxylumichromes were absent from urine of riboflavin-deficient rats. Riboflavin accounted for 85-90% of the recovered radioactivity of all radioactive urine extracts; no radioactively labeled carboxylumichromes were detected. These results indicate that hydroxymethylriboflavins are primary catabolites of riboflavin derived from tissue microsomal oxidations, whereas carboxylumichromes reflect the continued oxidation of ring hydroxymethyl functions plus gut microbial cleavage of the side chain of flavin.

Irradiated Riboflavin Diminishes the Aggressiveness of Melanoma In Vitro and In Vivo

“…This apparent discrepancy between in vitro and in vivo , was not due to toxic effects of RF in melanoma cells, but might be due to the metabolization of RF in vivo , which also provides photoproducts as main catabolites. It has been shown by Ohkawa et al (1983) [35] and Chastain and McCormick (1987) [36] that RF photodecomposition can occur in the human body.…”

“…It has been shown by Ohkawa et al (1983) [35] and Chastain and McCormick (1987) [36] that RF photodecomposition can occur in situ in the human body. Our group showed that irradiated RF (iRF) has a strong anti-tumoral effect on leukemia cells [37], as well as anti-proliferative and anti-metastatic effects on solid tumors [34].…”

Transcriptional Regulation of the Albumin Gene Depends on the Removal of Histone Methylation Marks by the FAD-Dependent Monoamine Oxidase Lysine-Specific Demethylase 1 in HepG2 Human Hepatocarcinoma Cells

“…In most cases, flavocoenzymes are not covalently attached to apoproteins but form noncovalent complexes (4). Flavin metabolites other than riboflavin, FMN, and FAD were identified in human plasma and urine by McCormick and coworkers (5)(6)(7)(8), but these metabolites probably lack biologic activity.…”

Micronutrient cofactor research with extensions to applications

“…When this vitamin is irradiated with light at wavelengths that are in the visible range (and hence is not absorbed by simple proteins), the flavin excited state can interact with nucleic acids contained within viral and bacterial pathogens to effect photo-oxidation, especially of guanine residues, to cause killing of such organisms. The side-chain photoproducts of riboflavin that result are mainly those that we have shown are excreted in urine (Chastain & McCormick, 1987a,b, 1988 and are secreted in milk from cows (Roughead & McCormick, 1990a) and human subjects (Roughead & McCormick, 1990b). Fig.…”