2.2. MTT Assay and CCK-8 Assay for Cell Viability and Proliferation

It mainly referred our previous report [35]. In detail, cells were seeded in a 96-well plate at a density of 1 × 10⁴ cells/well overnight and treated with different concentrations of phloretin (0, 20, 50, and 100 μM) for 24 h, and then culture medium was removed and fresh medium (100 μl) was added with 10 μl of MTT (5 mg/ml) or 5 μl of CCK-8 solution. The plate was incubated at 37°C for 4 h in the dark. For CCK-8 assay, the absorbance of the incubations was measured using a microplate reader (Thermo Scientific, Fremont, CA, USA) at 450 nm. For MTT assay, the medium was removed again, and 100 μl of DMSO was added to each well and the absorbance at 570 nm was measured by a microplate reader (Thermo Scientific, Fremont, CA, USA).

All the measured OD values were converted into cell viability and compared with the value of the control well.