Inhibitory Effects of Lignans and Flavonoids in Saiboku-To, a Herbal Medicine for Bronchial Asthma, on the Release of Leukotrienes from Human Polymorphonuclear Leukocytes

Abstract

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 Ca²⁺-ionophore A23187.All phenolic compounds exhibited dose-dependent suppression on release of both LTB₄ and LTC₄, while triterpenoids did not show any effects, except for glycyrrhetinic acid, which selectively inhibited LTC₄-release. The five phenolic compounds, magnolol, dihydroxydihydromagnolol, baicalein, medicarpine and davidigenin, were found to exert a marked inhibition on LTB₄- and LTC₄- release with IC₅₀ values of 0.7–15.3µM. The results suggest that the phenolic compounds contribute to the anti-allergic effects of Saiboku-To through suppression of LT-release from PMLs.

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