2.3. In Vitro Cytotoxicity Assay

In vitro cytotoxicity was measured by an MTT assay. HepG2, Huh-7, SMMC-7721, HCC-LM3, HLE and LX2 cells were seeded in 96-well plates at a density of 1 × 10⁴ cells/well for 24 h. Afterwards, different concentrations of ginsenoside CK (2.5–100 μM) and CoCl₂ (50–500 μM) were added. After incubating for an additional 48 h, MTT (0.5 mg/mL) was added and cultured for 2–4 h. Finally, MTT was removed carefully followed by addition of 150 μL DMSO to each well, and the plates were detected by a microplate reader (Bio-Tek Instruments, Inc., Winooski, VT, USA) at 490 nm. Each data point was an average of the values of six replicates at each concentration.