Isatis root 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 leaf and other herbs to treat the common cold, sore throat, mumps, respiratory ailments, other febrile diseases, hepatitis, and malignant tumors (1) (2). One such formula, Danggui Longhui Wan, is used in China to treat chronic myelocytic leukemia (CML) (3). Isatis root has also been promoted to ward off severe acute respiratory syndrome (SARS).
In vitro assays have identified specific compounds in isatis root with potential anti-SARS (4) and anti-influenza activity (5), as well as cytotoxic activity against human liver cancer and leukemia cell lines (6). Several in vitro and animal studies also demonstrate antimicrobial (7), antiviral (8) (9), anti-endotoxic (10), immunostimulatory (3) (11), chemotherapeutic (12), and radioprotective effects (13). Animal models indicate anti-inflammatory, antipyretic, and antinociceptive effects (13) (14).
In one clinical trial, isatis root eyedrops were an effective treatment for bacterial conjunctivitis (7). A small randomized clinical study demonstrated its utility for reducing the severity of radiation mucositis (15).
Isatis leaf has both overlapping and different properties from isatis root.