Complexing of riboflavin with the enolate form of barbituric acid

Malka Gorodetsky, Ruth F. Weiner, Wilhelm R. Frisell

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Riboflavin and the enolate form of barbituric acid form a complex at pH 7.80 as demonstrated by the appearance of two new absorption bands at 400 and 490 nm. The association constant for the complex determined from a Benesi-Hildebrand analysis of absorbances at 490 nm is 30 M-1. The K evaluated from fluorescence quenching at various barbiturate: riboflavin ratios is 33 M-1. The complexing of the barbiturate and riboflavin is accompanied by an inhibition of the photo-oxidation of sarcosine to formaldehyde. Under the same conditions, the barbiturate enhances the rate of photo-oxidation of NADH. The 5,5-disubstituted barbiturates do not give a new absorption band with riboflavin and do not inhibit the photo-oxidation of sarcosine, indicating that an enolate configuration of the β-diketone system is involved in complexing with riboflavin.

Original languageEnglish
Pages (from-to)582-585
Number of pages4
JournalBiochimica et Biophysica Acta - Bioenergetics
Issue number2
StatePublished - 28 Feb 1972
Externally publishedYes

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology


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