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 eight phenolic compounds, which have been identified as the major human metabolites of Saiboku-To, and three triterpenoids contained in Saiboku-To on the release of leukotriene (LT) from human polymorphonuclear leukocytes (PMLs) stimulated with Ca 2+ -ionophore A23187. All phenolic compounds exhibited dose-dependent suppression on release of both LTB 4 and LTC 4 , while triterpenoids did not show any effects, except for glycyrrhetinic acid, which selectively inhibited LTC 4 -release. The five phenolic compounds, magnolol, di-hydroxydihydromagnolol, baicalein, medicarpine and davidigenin, were found to exert a marked inhibition on LTB 4 - and LTC 4 -release with IC 50 values of 0.7 -15.3 μM. The results suggest that the phenolic compounds contribute to the anti-allergic effects of Saiboku-To through suppression of LT-release from PMLs.