Woad / Isatis / Da Qing Ye

Woad (Isatis tinctoria) is a blue dye plant native to Europe and Central Asia, closely related to Chinese Isatis indigotica (Da Qing Ye). Both species contain indirubin — a red isomer of indigo with extraordinary anti-leukaemic properties. Indirubin was isolated as the active component of a traditional Chinese medicine used clinically in China for chronic myelogenous leukaemia (CML) treatment since the 1980s, showing ~26% complete haematological response rates. Indirubin inhibits cyclin-dependent kinases (CDK1, CDK5) and STAT3 — pathways critical for leukaemia cell survival. Indirubin-3'-monoxime and other synthetic derivatives are now in clinical trials. Beyond leukaemia, indirubin shows anti-proliferative activity against glioblastoma, breast, and colon cancers. This represents one of the clearest examples of traditional European + Chinese medicine converging on the same active compound.