4.2. Cell Viability

Cell viability was measured using an MTT assay, as previously described [46]. Hep3B cells were seeded on 96-well plate at a density of 5 × 10³ cells per well. After 24 h of incubation, the cells were treated with different concentrations of coptisine, for 24 h, in the presence or absence of NAC (Sigma-Aldrich Chemical Co.). Subsequently, the cells were incubated with 0.5 mg/mL MTT (AMRESCO) solution, at 37 °C. After incubation for 2 h, the medium was removed, and then 200 µL of DMSO was added to the well to dissolve the formazan. The cell viability was determined by measuring the optical density at 540 nm with a microplate reader (VERSA Max, Molecular Device Co., Sunnyvale, CA, USA).