Isatis tinctoria – From the rediscovery of an ancient medicinal plant towards a novel anti-inflammatory phytopharmaceutical

An account on the reinvestigation of the old dye and medicinal plant Isatis tinctoria as an anti-inflammatory and current research on the active principles in woad is given. In a broad-based screening, a dichloromethane extract from the leaves displayed significant activities on several clinically relevant targets of inflammation. The cyclooxygenase-2 inhibitory principle was identified with the aid of HPLC-based activity profiling as the alkaloid tryptanthrin. In cell based assays, tryptanthrin strongly inhibited eicosanoid synthesis catalyzed by cyclooxygenase-2 and 5-lipoxygenase. A supercritical carbon dioxide extraction process was developed to replace the dichloromethane extract. Dichloromethane and carbon dioxide extracts showed in vivo anti-inflammatory activity in topical and oral application. With the aid of electrospray ionization liquid chromatography-mass spectrometry coupled skin microdialysis, tryptanthrin was found to penetrate the skin. The penetration from the extract was better than for the pure alkaloid. A screening of 67 woad samples of different geographic origin revealed up to 30-fold differences in tryptanthrin content in leaves.