4.1. Chemicals

Mangiferin and norathyriol were purchased from BioBioPha Co. (Yunnan, China), and the purity of these two compounds was demonstrated to be above 95%. Sigma-Aldrich (St Louis, MO, USA) provided the following constituents in the incubation mixture: 4-methylumbelliferone (4-MU), 4-methylumbelliferone-β-d-glucuronide (4-MUG), Tris-HCl, 7-hydroxycoumarin, and uridine-diphosphoglucuronic acid (UDPGA) (trisodium salt). All other compounds were of high-performance liquid chromatography (HPLC) grade or of the highest grade commercially available. For enzyme sources, recombinant UGT isoforms expressed in baculovirus-infected insect cells were purchased from BD Gentest Corp. (Woburn, MA, USA), including UGT1A1, 1A3, 1A6, 1A7, 1A8, 1A9, 1A10, 2B4, 2B7, 2B15, and 2B17.