Sulfation of selected mono-hydroxyflavones by sulfotransferases in vitro: a species and gender comparison

OBJECTIVES: Sulfation via sulfotransferases is an important metabolic pathway contributing to the low bioavailability of flavonoids. This study aims to characterize the sulfation of mono-hydroxyflavones (MHFs) to obtain useful information on structure-metabolizing relationships in animal species and gender differences. METHODS: Three representative MHFs, namely, 7-, 6- and 4'-MHF, were studied by incubating each MHF at different concentrations with various liver S9 fractions (mouse, rat, dog and human). KEY FINDINGS: One mono-sulfate was identified for each MHF. 7-MHF and 4'-MHF usually have greater sulfations than 6-MHF. Regardless of whether the S9 fraction came from a male or female, there was a difference in sulfation in the species observed for all MHFs; the highest activity of sulfotransferases was in dog S9. Furthermore, gender differences affect sulfation of MHFs significantly. In rats, all sulfations for the three MHFs were higher in males than that in females while the opposite was observed in mice. CONCLUSIONS: Regiospecific, species and gender dependence exist in the sulfonation of all selected MHFs.