Photophysical properties of lumichromes in water.

The photophysics of lumichrome, 1-methyllumichrome, and lumiflavin in water solutions have been investigated. Fluorescence lifetimes of 2.7 and 2.2 ns were observed for lumichrome and 1-methyllumichrome, respectively, the corresponding triplet state lifetimes of 17 and 18 micros have been obtained from the transient absorption spectra. Evidence for long lived species with absorption maxima near 450 nm and lifetimes of ca. 400 micros has been found in the transient absorption spectra of both lumichromes. Quantum yields for the sensitised production of singlet oxygen, phi(Delta), are 0.36 and 0.41 for lumichrome and 1-methyllumichrome, respectively, in D(2)O.

Chromatographic determination of riboflavin and its derivatives in food.

Three elution methods on two different reversed-phase C18 columns were developed to determine flavin derivatives in raw egg white, raw egg yolk, egg powder, pasteurised milk, fermented milk products and liver (chicken, calf and pig). Additionally, 11 thin-layer chromatography solvent systems were used to confirm presence of flavins detected in assessed products. It was found that an Alphabond C18 column was not as effective as a Symmetry C18 column. Method A (mobile phase gradient of methanol-0.05 M ammonium acetate, pH 6.0 applied on an Alphabond C18 column) can be used for determination of flavin adenine dinucleotide, flavin mononucleotide, riboflavin 4',5'-cyclic phosphate, riboflavin, 10-formylmethylflavin and 10-hydroxyethylflavin in products that do not contain 7alpha-hydroxyriboflavin. Method B (mobile phase gradient of methanol-demineralized water, on an Alphabond C18 column) can be useful to separate flavin coenzymes from other flavin compounds or to confirm the presence of 7alpha-hydroxyriboflavin and 10-hydroxyethylflavin in analysed samples. Method C (mobile phase gradient of methanol-0.05 M ammonium acetate, pH 6.0, on a Symmetry C18 column) allows separation of all flavins detected in tested products: flavin adenine dinucleotide, flavin mononucleotide, riboflavin 4',5'-cyclic phosphate, riboflavin, 10-formylmethylflavin, 10-hydroxyethylflavin, 7alpha-hydroxyriboflavin, riboflavin-beta-D-galactoside and riboflavin-alpha-D-glucoside.

Chromatographic identification of a new flavin derivative in plain yogurt.

The presence of flavin derivatives in plain yogurt was assessed by high-performance liquid chromatography (HPLC) and thin-layer chromatography (TLC). The total amount of flavins in yogurts produced by different companies was variable and oscillated between 150.0 and 218.8 microg/100 g. Riboflavin (RF) was the predominant flavin. Besides RF, flavin adenine dinucleotide (FAD), flavin mononucleotide (FMN), 7alpha-hydroxyriboflavin (7alpha-HRF), 4'- or 5'-D-riboflavin-beta-D-galactoside (RFgal), and traces of 10-formylmethylflavin (10-FMF) and 10-hydroxyethylflavin (10-HEF) have been found. It is known that RFgal may be obtained using enzymes or cultures of different microorganisms, but its presence in foodstuffs has not been demonstrated, yet.

Chromatographic determination of flavin derivatives in baker's yeast.

The presence of flavin derivatives in baker's yeast was tested by high-performance liquid chromatography and thin-layer chromatography. In yeast samples, besides flavin adenine dinucleotide and flavin mononucleotide, small amounts of riboflavin and traces of 10-formylmethylflavin have been found. Total amount of flavins was calculated to be 17.9 +/- 2.9 micrograms/g of fresh yeast. The distribution of flavin adenine dinucleotide, flavin mononucleotide, riboflavin and 10-formylmethylflavin in total flavin content were estimated to be 71.5%, 25.8%, 1.7% and below 0.05%, respectively. In some samples we have additionally detected small amounts (0.8% of total flavins) of new flavin derivative which has been identified as 4',5'-riboflavin cyclic phosphate by means of its chromatographic and chemical behaviour. This compound seems to be a product of flavin adenine dinucleotide degradation and probably has been earlier mistaken for flavin mononucleotide. Its formation is dependent on pH conditions.