2.6. Cell Proliferation Assay

MTT assay was used to measure cell proliferation. Briefly, A549 cell lines were seeded in 96-well culture plates at a density of 5 × 10³ cells per well in complete medium, incubated overnight to allow attachment, and divided into different groups (n = 6). The cells in the control group were treated with culture medium, while others were treated with culture medium containing different concentrations of GJXTL (8.88–568.00 μg/mL) for 12, 24, and 36 h. Then, the cells were incubated with 100 μL of 0.5 mg/mL MTT at 37°C for 4 h, and the precipitate was dissolved in 150 μL dimethylsulfoxide (DMSO). After shaking for 10 min, optical density (OD) was measured at a wavelength of 570 nm and a reference wavelength of 0 nm using a multimode reader (Synergy HTX, BioTek, USA). The inhibition rate was calculated as follows: Inhibition rate (%) = [average OD value (control) − average OD value (medication)]/average OD value (control) × 100%. The IC50 value was calculated on the non-linear regression fit method by the SPSS statistics software (Statistical Product and Service Solution, IBM, New York, USA).