Fig. 3

Structure-activity relationship of flavonoid derivatives exhibiting inhibitory activities against AeNobo. A, B Chemical structures of daidzein derivatives (A) and luteolin derivatives (B), which possess isoflavone and flavone nuclei, respectively. Red dashed circles indicate the hydroxyl residues that form hydrogen bonds with Glu-113 of AeNobo. C, D Inhibition of the GSH conjugation activities of AeNobo using 3,4-DNADCF in the presence of daidzein derivatives (C) and of luteolin derivatives (D). Each relative activity is defined as the ratio of activity compared between the respective proteins without the flavonoids. All the data points in duplicate assays are indicated