Cell Viability Assay

The cell viability assay was performed using the Cell Counting Kit-8 (CCK-8). Briefly, OVCAR-3 cells were seeded into 96-well plates at a density of 6 × 10³ cells per well. In the time-course and dose-dependent experiments, different concentrations of garcinol (0, 5, 10, 20, 25, 30, and 50 μM) were applied in individual wells. Empty (blank, without a cell) and cells without a drug were used as controls. Five replicates were applied. After incubation for 24, 48, and 72 hours, 10 µL of CCK-8 reagent was added into each well. The cell viability was evaluated by reading the absorbance of optical density (OD) at 490 nm using a microplate reader (BioRad).

For the combination of garcinol and DDP experiments, cells were divided into 3 groups: garcinol alone at different doses (0, 5, 10, 20, 25, and 30 μM), DDP alone at different doses (0, 0.5, 1, 2, 4, and 8 μM), and the combination of garcinol and DDP. Five replicate wells were set for each concentration. After cells were treated for 48 hours, 10 µL of CCK-8 reagent was added to each well and incubated at 37°C for 1 hour. The OD was measured at 490 nm using a microplate reader. To calculate the inhibition rate of cell proliferation, the following equation was used:

Inhibition Rate (%) = (1 − OD value of treated cells / OD value of untreated cells) × 100%.

The half-maximal inhibitory concentration (IC₅₀) of the drug was also calculated and guided to the subsequent experiments.