Mammalian two-hybrid assays were performed in HepG2 cells transiently cotransfected with plasmids encoding Gal4-SRC-1 and the reporter gene pG5-luc, along with empty vector pACT as indicated. (A) The cells were treated with DMSO, 5 μM rifampicin, or 3 μM compound 1, 2, 3, 4, or 7. * Indicates p < 0.05 (comparisons were made between compound 1, 2, 3, 4, or 7 and DMSO control for samples transfected with pACT-hPXR). (B) Cells were treated with DMSO, 5 μM rifampicin, or 10 μM compound 5, 6, or 8 in the presence of 5 μM rifampicin (Rif) 24 h after transfection. Luciferase assays were performed 24 h after the compound treatment. The relative luminescence for pG5-luc was determined by normalizing firefly luciferase activity with Renilla luciferase activity. The values represent the means of five independent experiments, and the bars denote the S.D. * Indicates p < 0.05 for samples transfected with pACT-hPXR (samples co-treated with rifampicin and either compound 5, 6, or 8 were compared to rifampicin control; the difference between rifampicin and DMSO is also statistically significant with p < 0.05).