Inhibitory effects of lignans and flavonoids in Saiboku-To, a herbal medicine for bronchial asthma, on the release of leukotrienes from human polymorphonuclear leukocytes

To identify the anti-allergic components contained in Saiboku-To, a herbal medicine for the treatment of bronchial asthma, we studied the effects of e ight phenolic compounds, which have been identified as the major human meta bolites of Saiboku-To, and three triterpenoids contained in Saiboku-To on t he release of leukotriene (LT) from human polymorphonuclear leukocytes (PML s) stimulated with Ca2+-ionophore A23187. All phenolic compounds exhibited dose-dependent suppression on release of both LTB4 and LTC4 while triterpen oids did not show any effects, except for glycyrrhetinic acid, which select ively inhibited LTC4-release, The five phenolic compounds, magnolol, dihydr oxydihydromagnolol, baicalein, medicarpine and davidigenin, were found to e xert a marked inhibition on LTB4- and LTC4-release with IC50 values of 0.7- 15.3 mu M. The results suggest that the phenolic compounds contribute to th e anti-allergic effects of Saiboku-To through suppression of LT-release fro m PMLs.