Lobetyolin is derived from Codonopsis pilosula and has antioxidative effect. MUC5AC gene expression induced by phorbol 12-myristate 13-acetate (PMA) from NCI-H292 cells is inhibited by pretreatment with Lobetyolin, lobetyol or methyl linoleate. Lobetyolin does not affect PMA-induced MUC5AC production from NCI-H292 cells. The amounts of mucin in the cells of Lobetyolin-treated cultures are 100±25%, 487±33%, 524±38%, 411±24%, and 402±45% for control, 10 ng/mL of PMA alone, PMA plus Lobetyolin 1 μM, PMA plus Lobetyolin 10 μM, and PMA plus Lobetyolin 100 μM, respectively.