Inhibitory Effect of Baicalein, a Flavonoid in Scutellaria Root, on Eotaxin Production by Human Dermal Fibroblasts

Abstract

Eotaxin is an eosinophil-specific chemokine associated with the recruitment of eosinophils to sites of allergic inflammation. „Saiboku-to” (Formula magnoliae et bupleuri) is a kampo herbal medicine used for the treatment of bronchial asthma in Japan. In this study, we investigated the effects of Scutellaria Root, a major herb in Saiboku-to and its components such as baicalein and baicalin on eotaxin production by IL-4 plus TNF-α-stimulated human 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 μg/ml in the order of baicalein > oroxylin A > baicalin > skullcapflavon II. The inhibitory effect of baicalein was expressed in a dose-dependent manner, and almost 50 % inhibition was observed at 1.8 μg/ml. Furthermore, baicalein prevented human eotaxin mRNA expression in IL-4 plus TNF-α-stimulated human fibroblasts. These results help explain the pharmacological efficacy of Scutellaria Root in the treatment of bronchial asthma since it would suppress eotaxin associated recruitment of eosinophils.

Key words

Baicalein - eotaxin - Scutellaria Root - chemokine - Saiboku-to - flavonoep

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