Inhibitory effect of baicalein, a flavonoid in Scutellaria root, on eotaxin production by human dermal fibroblasts

Eotaxin is an eosinophil-specific chemokine associated with the recruitment of eosinophils to sites of allergic inflammation. "Saiboku-to" (Formula ma gnoliae et bupleuri) is a kampo herbal medicine used for the treatment of b ronchial asthma in japan. In this study, we investigated the effects of Scu tellaria Root, a major herb in Saiboku-to and its components such as baical ein and baicalin an eotaxin production by IL-4 plus TNF-alpha -stimulated h uman fibroblasts. An extract of Scutellaria Root markedly inhibited eotaxin production. Four major flavonoids from Scutellaria Root were found to show inhibitory activity on eotaxin production at a concentration of 10 mug/ml in the order of baicalein > oroxylin A > baicalin > skullcapflavon II. The inhibitory effect of baicalein was expressed in a dose-dependent manner, an d almost 50% inhibition was observed at 1.8 mug/ml. Furthermore, baicalein prevented human eotaxin mRNA expression in IL-4 plus TNF-alpha -stimulated human fibroblasts, These results help explain the pharmacological efficacy of Scutellaria Root in the treatment of bronchial asthma since it would sup press eotaxin associated recruitment of eosinophils.