Antioxidant and iron-chelating properties of taxifolin and its condensation product with glyoxylic acid.

The condensation of taxifolin with glyoxylic acid was examined, and the properties of the resulting product were compared with those of taxifolin. The structure of the product was determined by NMR spectroscopy. The ability of the polyphenols to scavenge reactive oxygen species (ROS) was estimated by luminol-dependent chemiluminescence. The iron-chelating and iron-reducing activities were studied using absorption spectrophotometry. It was shown that the condensation leads to the formation of a dimer consisting of two taxifolin units linked through a carboxymethine bridge at the C-6 and C-8 positions of the A ring. The dimer exhibited a somewhat higher ROS scavenging activity than taxifolin. The iron-binding capacity of the compounds was proportional to the number of polyphenol units. The iron-reducing ability of the dimer was lower than that of taxifolin. Thus, the dimer possessed a higher antioxidant activity than the parent flavonoid. The data obtained may be useful for a better understanding of processes occurring in foods and beverages and in a search for new active compounds.