
Dyer’s woad leaf, Indigo, Da Qing Ye
Derived from the leaves of the isatis plant, a source of indigo dye. This botanical has been used for thousands of years in traditional Chinese medicine and Ayurvedic medicine. It is used in combination with isatis root and other herbs to treat common cold, sore throat, mumps, respiratory aliments, other febrile diseases and malignant tumors. The pulverized form, known as Qing Dai, has been used topically to treat oral sores and sore throat (1) (2). Isatis is one of the eight 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 (7). Studies indicate that isatis has antimicrobial, antiviral (1) (8), immunostimulatory (6) and anti-inflammatory (9) properties. Recent anecdotal reports indicate that isatis root can be used to ward off severe acute respiratory syndromes (SARS) (4). Adverse effects from consuming isatis leaves include nausea and vomiting (2).
Extracts obtained from the dried leaves of isatis have cyclooxygenase-2 (COX-2) inhibitory effects.(4) Indirubin, an active component of isatis, is a potent inhibitor of cyclin-dependent kinases (CDKs). It inhibits the proliferation of cells by arresting the cells in the G2/M phase.(7) Other alkaloids isolated from isatis can inhibit the function of leukocytes and can reduce inflammatory responses.(5) Some studies have shown that isatis also has antiendotoxic and antiviral activities.(8)
An active component of isatis leaf, indican, when given orally to rabbits produced a maximum plasma concentration after 3 hours. Sites of distribution included the liver, kidney, muscle, and gastrointestinal tract. 90% of indican was excreted through the kidney.(2)
Common: Nausea and vomiting.
Reported: Hematuria following intramuscular injection.(2)
Heinemann C, Schliemann-Willers S, Oberthür C, Hamburger M, Elsner P. Prevention of experimentally induced irritant contact dermatitis by extracts of Isatis tinctoria compared to pure tryptanthrin and its impact on UVB-induced erythema. Planta Med. 2004 May;70(5):385-90.
Bottom Line: Isatis leaf has not been tested in clinical trials, so it is not known if it works in humans. It should not be used to treat SARS, HIV, or other serious diseases.
Isatis leaf extract is derived from the same plant from which indigo dye is made. It has been used in combination with other botanicals in traditional Chinese and Ayurvedic medicine for thousands of years. Isatis extracts have been found to be COX-2 inhibitors, which indicates that they may have anti-inflammatory and pain-relieving properties. (Other COX-2 inhibitors include aspirin and ibuprofen). Laboratory studies have also suggested that indirubin, an active component of isatis root, inhibits the replication of dividing cells and therefore may be useful in cancer treatment. In the laboratory setting, isatis extracts are able to kill certain viruses and counteract the effects of endotoxin, which causes some of the symptoms and tissue damage of bacterial infections. However, this botanical has not yet been evaluated in clinical trials and therefore it remains uncertain whether these effects occur in the human body.