Isatis leaf is derived from the isatis plant and is a source of indigo dye. In both traditional Chinese medicine (TCM) and Ayurveda, it is used in combination with isatis root and other herbs to treat the common cold, sore throat, mumps, respiratory ailments, other febrile diseases, hepatitis, and malignant tumors (1) (2). The pulverized form, known as Qing Dai, has been used to treat ulcerative colitis (3), and topically to treat oral sores and sore throat. Isatis leaf is one of the ingredients used in PC-SPES, an herbal formula used to treat prostate cancer. It is also used in Danggui Longhui Wan, a formula used to treat chronic myelocytic leukemia (CML) in China (4).
In vitro and in vivo studies indicate that isatis has antimicrobial, antiendotoxic (5), antiviral (6) (7) (8), immunostimulatory (9), anti-inflammatory (10) (11), and chemotherapeutic (12) properties. In several instances, the pharmacologic effects of isatis leaves were found to be greater than that of the roots (5) (8). A small preliminary study in healthy volunteers has also indicated anti-inflammatory (13) properties with topical isatis leaf.
Isatis root has both overlapping and different properties from isatis leaf.