Inhibition of Proinflammatory Cytokine Generation in Lung Inflammation by the Leaves of Perilla frutescens and Its Constituents

This study was designed to find some potential natural products and/or constituents inhibiting proinflammatory cytokine generation in lung inflammation, since cytokines such as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) are pivotal for provoking airway inflammation. In our preliminary screening procedure, the 70% ethanol extract of the leaves of Perilla frutescens (PFE) was found to clearly inhibit TNF-α production in the lung at 100 mg/kg, after intranasal lipopolysaccharide treatment of mice. Based on this result, ten constituents including phenylpropanoids (allyltetramethoxybenzene, caffeic acid, dillapiole, elemicin, myristicin, nothoapiole, rosmarinic acid methyl ester, rosmarinic acid) and monoterpenes (perilla aldehyde and perilla ketone) were successfully isolated from the extract. Among them, elemicin and myristicin were found for the first time to concentration-dependently inhibit IL-1β-treated IL-6 production from lung alveolar epithelial cells (A549) at concentrations of 10-100 μM. These findings suggest that the phenylpropanoids including elemicin and myristicin have the potential to be new inhibitory agents against lung inflammation and they may contribute, at least in part, to the inhibitory activity of PFE on the lung inflammatory response.