*5.5. Cell Culture and Cell Viability Measurement*

Murine macrophage cell line RAW 264.7 were cultured in Dulbecco's Modified Eagle Medium (DMEM, Hyclone Florida, USA) supplemented with 10% fetal bovine serum (FBS, ExCell Bio Shanghai, China), 1% Penicillin Streptomycin (Gibico California, USA) at 37 ◦C in a humidified atmosphere of 95% air and 5% CO2. After spreading at 80–90% confluence, cells were washed with PBS, scraped with fresh culture, and subcultured into 96-well plates at a density of 5.0 <sup>×</sup> 103 cells/well and incubated with or without LPS (1 μg/mL). The cells were exposed to different concentrations of gentiopicroside, loganic acid, swertiamarin, and vitexin (0, 1, 5, 10, 20, 40, and 50 μM) with or without LPS (1 μg/mL) for 24 h. The optical density was measured at 450 nm using a multi-plate reader (BioTek, Winooski, VT, USA).
