Qing-Dai (Sei-tai) is a herbal preparation containing indigo and indirubin, which derived from the stems and leaves of Strobilanthes cusia and Indigoferatinctoria. It has been traditionally used not as only blue dyes, but also as anti-inflammatory medicines. Recently, several clinical reports have shown a remarkable effect of Sei-tai to treat ulcerative colitis (UC). In our previous pharmacological experiments, Sei-tai considerably inhibited LPS-induced cytokine expression in cultured gastric epithelial cells and inhibited DSS-induced UC in mice. Indigo, a major component of this medicine, is known to activate a nuclear receptor Aryl hydrocarbon receptor (AhR) and have anti-inflammatory effect. However, after the fractionation of Sei-tai, potent inhibitory effect on cytokine expression was obtained from water soluble fraction, which doesn’t contain indigo. This new active component of Sei-tai dose-dependently inhibited cytokine expression both in vitro and in vivo, as well as indigo, whereas it did not activate AhR. Now, we are investigating the characteristics of the pharmacological action of this new component.