|Perilla frutescens was empirically used for controlling airway inflammatory diseases in folk medicine. We investigated whether caffeic acid, myristicin and rosemarinic acid derived from Perilla frutescens significantly affect the gene expression and production of mucin from airway epithelial cells. Confluent NCI-H292 cells were pretreated with caffeic acid, myristicin or rosemarinic acid for 30 min and then stimulated with phorbol 12-myristate 13-acetate (PMA) for 24 h. The MUC5AC mucin gene expression and production were measured by reverse transcription - polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA), respectively. Additionally, we examined whether caffeic acid, myristicin or rosemarinic acid affects MUC5AC mucin production indued by epidermal growth factor (EGF) and tumor necrosis factor-α (TNF-α), the other two stimulators of production of airway mucin. The results were as follows: (1) Caffeic acid, myristicin and rosemarinic acid inhibited the gene expression and production of MUC5AC mucin induced by PMA from NCIH292 cells, respectively; (2) Among the three compounds derived from Perilla frutescens, only rosemarinic acid inhibited the production of MUC5AC mucin induced by EGF or TNF-α, the other two stimulators of production of airway mucin. These results suggest that rosemarinic acid derived from Perilla frutescens can regulate the production and gene expression of mucin, by directly acting on airway epithelial cells and, at least in part, explains the traditional use of Perilla frutescens as remedies for diverse inflammatory pulmonary diseases.