Woad, also known as Isatis root, Daqinggen, Beibanlan, etc., is a plant of the genus Isatis in the Brassicaceae family, and its roots and leaves are used as medicine. Its root is called Isatis root in Chinese medicine, its leaves are called Daqingye, and the dark blue powder made from fresh leaves or stems and leaves is called Indigo Naturalis. All three are commonly used Chinese medicines. The roots contain myrosin, indolein, isatin, β-sitosterol, isatisin, protinin, ditinin, indigo, indirubin, and various amino acids.

Cold in nature and bitter in taste, it has the effects of clearing away heat, detoxifying and cooling blood. It is mainly used to treat influenza, mumps, Japanese encephalitis, epidemic cerebrospinal meningitis and acute infectious hepatitis. , sore throat, tonsillitis, carbuncle and sores. The leaves contain about 1% of woad glycoside, and also contain mustardin, neoglucoside, 1-sulfoginsin, free indol alcohol and oxidase.

It is cold in nature, bitter and salty in taste, and has the same effect as the root. Indigo contains more than 5% indigo, and also contains indirubin, indigo, tryptophan, etc. It is cold in nature, bitter and salty in taste, and has the same effects as roots and leaves. Tryptophan isolated from Indigo Naturalis can fight skin fungi; indirubin is an effective ingredient in the treatment of chronic myelogenous leukemia.

Woad is cultivated all over the country. It is mainly produced in Nantong area of ??Jiangsu Province, Anguo County of Hebei Province, and Henan, Shaanxi, Anhui and other provinces. The quality of woad produced in Anguo, Hebei Province is especially the best.