Isatidis Folium Isatidis Folium is the dried leaf of Isatis tinctoria L. (I.indigotica fortune ex Lindl.), family Brassicaceae (Cruciferae). It has anti-viral activity against influenza A virus, herpes simplex virus-1, Coxsackie virus-B3, respiratory syncytial virus, mumps virus, etc. Isatidis Folium has anti-bacterial activity against several kinds of bacteria and has strong anti-bacterial activity against Staphylococcus aureus. It has strong anti-endotoxin activity. It has distinctive anti-pyretic and anti-acute inflammatory activities. The active constituents related to the anti-inflammatory activity are total organic acids. Isatidis Folium can enhance the immune function, the active substances are indirubin and tryptanthrin. Indirubin also has strong inhibitory effect on proliferation of transplanted tumor in experimental animals, and effective in treating chronic myelogenous leukemia. Bitter in flavor, cold in nature. Enter heart and stomach channels. Clear heat and remove heat toxin, cool the blood and remove ecchymosis.