HepG2 cells were cultivated in DMEM solution containing 10%FBS at 37°C in 5% CO2. 2 × 105 HepG2 cells were platted in 6-well plate and cultivated for 6 h, and then changed the culture medium to DMEM solution without FBS. Twenty-five hours later, 0.25, 0.5, 1 mM SA, OA, LA, and ALA standards (Sigma, St. Louis, MO, USA) prepared via saponification and albumin binding were added into culture medium, respectively. A 24 h incubation was needed before harvesting the cells for Nrf2 and CYP2A6 levels detection.
