Bisnorbiotin methyl ketone

Zempleni, J. McCormick, B. Mock, D.M. Identification of biotin sulfone, bisnorbiotin methyl ketone, and tetra-norbiotin-I-sulfoxide in human urine. Am. J. Clin. Nutr. 1997, 65, 508-511. 

About half of the absorbed biotin is excreted as the metabolites bisnorbiotin, occurring from fl-oxidation of the valeric acid side chain, and biotin sulfoxide, occurring from the oxidation of the sulfur in the heterocyclic ring. The circulating plasma and urinary excretion patterns show a ratio of 3 2 1 for biotin, bisnorbiotin, and biotin sulfoxide. Minor metabolites are bisnorbiotin methyl ketone and biotin sulfone. Careful balance studies in humans, where perhaps only 1 mg is the total body content, showed that urinary excretion of biotin often exceeded dietary intake, and that in aU cases, fecal excretion was as much as three to six times greater than dietary intake because of microfloral biosynthesis. 

Unidentified biotin metabolites were analyzed and identified in urine from healthy adults by TLC. " Three unknown biotin metabolites were identified as biotin sul-fone (Rf values 0.49 and 0.17), bisnorbiotin methyl ketone (Rf values 0.78 and 0.29), and tetranorbiotin-/-sulfoxide (/ f values 0.22 and 0.01) by derivatization with -demethylaminocinnamaldehyde after TLC on microcellulose with 1-butanol-acetic acid-water (4 1 1) and 1-butanol as solvents, respectively." ... 

Mock has described a very sensitive method (the limit of detection is around 5 fmol) for the detection of biotin and its metabolites, involving C18 reversed-phase HPLC separation followed by detection using an avidin-horseradish peroxidase conjugate (92). The principle of this method has already been discussed. This methodology has allowed the identification and quantification of biotin, bisnorbi-otin, biotin sulfoxides, and biotin sulfone in human and animal serum and urine. Furthermore, new biotin metabolites (tetranorbiotin sulfoxide and bisnorbiotin methyl ketone) were detected in human urine (114). This technique should potentiate more accurate studies on human biotin metabolism (see, e.g., 115). 

---