Inhibitory effects of C. petasites extracts and its active compounds on the pro-inflammatory cytokine release in Spike S1-induced A549 cells. A549 cells were pre-treated with C. petasites extracts (A), CpEE and CpEA, at a concentration of 0–200 μg/mL or active compounds (B), hesperidin or hesperetin, at a concentration of 0–20 μg/mL for 24 h. Then, the cells were exposed to Spike S1 (100 ng/mL) for 3 h. The IL-6, IL-1beta and IL-18 releases into the culture supernatant were examined by ELISA. The Spike S1-induced A549 cells are presented as 100%. Data are presented as mean ± S.D. values of three independent experiments, * p < 0.05, ** p < 0.01 and *** p < 0.001 vs. the Spike S1-induced control group. a
p < 0.05 vs. CpEE at the same concentration. b
p < 0.05 vs. hesperidin at the same concentration.