Abstract: Qing Dai, a traditional chinese medicine, is the fermentative product of the aerial part of Isatis indigotica Fort. Besides the two major constituents indigotin (Ⅰ) and indirubin (Ⅱ), four chemical constituents including a pigmental compound were isolated. By spectral analysis (IR, UV, MS, 1H and 13C NMR) and chemical cleavage the struture of this compound was eluci- dated as 6-indoxyl indolo (2, lb) quinazolone-12 (qingdainone, Ⅴ). Ⅴ was synthezised and its structure was comfirmed by condensation of tryptanthrin with indoxyl. The other compounds were identified as n-nonacosane, isatin (Ⅲ) and tryptanthrin (Ⅳ).

Key words: Qing Dai, Isatis indigotica Fort, isatin, tryptanthrin, qingdainone, 6-indoxyl indolo (2, lb) quinazolone-12