Active Lauraceae plant extracts protected human bronchial epithelial cells against H2O2-induced toxicity. A–F Cell survival in human bronchial epithelial cells untreated or pretreated with ZK-08 (60 μg/mL), ZK-02 (40 μg/mL), ZK-04 (60 μg/mL), ZK-05 (30 μg/mL), ZK-10 (60 μg/mL), and sulforaphane (3.0 μM) for 8 hours, and then treated with 100 or 200 μM H2O2 in the absence or presence of half of the pretreated doses of Lauraceae extracts and sulforaphane (2.0 μM) for 24 hours. G–K Cell survival was performed as described in A–F in human bronchial epithelial cells transfected with nuclear factor-erythroid 2-related factor 2-small interfering RNA. Values shown are the mean ± SD of experiments run in triplicate. *P < 0.05 vs. plant extract-treated group.