Sulfated Metabolites of Luteolin, Myricetin, and Ampelopsin: Chemoenzymatic Preparation and Biophysical Properties.

Authentic standards of food flavonoids are important for human metabolic studies. Their isolation from biological materials is impracticable; however, they can be prepared . Twelve sulfated metabolites of luteolin, myricetin, and ampelopsin were obtained with arylsulfotransferase from and fully characterized by high-performance liquid chromatography, MS, and NMR. The compounds were tested for their ability to scavenge 1,1-diphenyl-2-picrylhydrazyl, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid), and ,-dimethyl--phenylenediamine radicals, to reduce ferric ions and Folin-Ciocalteu reagent, and to inhibit -butyl hydroperoxide-induced lipid peroxidation of rat liver microsomes. The activity differed considerably even between monosulfate isomers. The parent compounds and myricetin-3'--sulfate were the most active while other compounds displayed significantly lower activity, particularly luteolin sulfates. No mutagenic activity of the parent compounds and their main metabolites was observed; only myricetin showed minor pro-mutagenicity. The prepared sulfated metabolites are now available as authentic standards for future and metabolic studies.