Indigo plant -- Isatis Indigotica -- Qing Dai

Indigo plant is used in China for infections associated with heat. See a list of Chinese herbs. It appears that indigo plant root has immune stimulating and anti-inflammatory activity.

Composition of the root
Zhongguo Zhong Yao Za Zhi. 2013. Chemical consitituents from root of Isatis indigotica]. Thirty-three compounds were isolated from the root decoction of Isatis indigotica. Their structures were elucidated by spectroscopic data as dehydrovomifoliol, abscisic acid, vomifoliol, cyclo (L-Phe-L-Leu) (4), cyclo(L-Phe-L-Tyr) (5), cyclo(L-Tyr-L-Leu) (6), cyclo(L-Pro-L-Tyr) (7), evofolin B, syringaresinol, 4,4'-dihydroxy-3-methoxy-7,9';7',9-diepoxy-lignan, medioresinol, (+) -(7R,7'R,8S,8'S) -neo-olivil (12), (-) -5-methoxyisolariciresinol (13), 1,3-dihydro-2H-indol-2-one (14), isalexin (15), dihydroneoascorbigen (16), indican (17), (-) -(S) -cyanomethyl-3-hydroxyoxindole (18), isoformononetein (19), calycosin (20), stigamast-5-ene-3beta-ol-7-one (21), acetovanillone (22), 3, 5-dimethoxy-4-hydroxyacetophenone (23), dihydroconiferyl alcohol (24), dihyroferulic acid (25), 3-hydroxy-1-(4-hydroxyphenyl) propan-1-one (26), beta-hydroxypropiovanillone (27), 4-aminobenzoic acid (28), 3-(4-hydroxyphenyl) propan-1-ol (29), 4-(2-hydroxyethyl) phenol (30), 2-methoxy-4-vinylphenol (31), pyrocatechol (32), and 4-pentenamide (33).

Indigo Plant Research trials
Bisindigotin, a TCDD antagonist from the Chinese medicinal herb Isatis indigotica - indigo plant.
J Nat Prod. 2005.
A new indigoid derivative, bisindigotin with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-antagonistic activity was isolated from the ethanol extract of the Chinese medicinal herb Isatis indigotica. Its structure was determined by spectroscopic methods. In the human HepG2 hepatoma cell model, it was found to dose-dependently inhibit TCDD-induced ethoxyresorufin O-deethylase (EROD) activity.

Evaluation on antiendotoxic action and antiviral action in vitro of tetraploid Isatis indigotica
Zhongguo Zhong Yao Za Zhi. 2000.
To evaluate the pharmacological effect of indigo plant. Comparing these actions of tetraploid I. indigotica with those of the diploid parent. These actions of tetraploid I. indigotica were obviously stronger than those of the diploid parent. The pharmacological effect of indigo plant leaves was greater than that of roots with identical ploidy. Tetraploid I. indigotica is a new line of better quality, deserving to be exploited and utilized on a large scale.

Studies on the antinociceptive, anti-inflammatory and anti pyretic effects of Isatis indigotica root.
Phytomedicine. 2002.
The root of indigo plant, popularly known as Ban-Lan-Gen is used in traditional Chinese medicine for seasonal febrile diseases, pestilence, mumps, eruptive diseases, inflammatory diseases with redness of skin, sore throat, etc. In this study, we evaluated the antinociceptive, antiinflammatory and antipyretic effects of indigo plant root methanolic extract. The results showed that indigo plant root extract significantly and dose-dependently inhibited the writhing responses of mice and decreased the licking time in both the early and late phases of the formalin test. It also reduced the paw edema induced by carrageenan in rats. In addition, it potently attenuated pyrexia induced by lipopolysaccharide.

Experimental studies on immunostimulatory effects of the Isatis indigotica polysaccharide
Zhong Xi Yi Jie He Za Zhi. 1991.
Polysaccharides extracted from the root of indigo plant (IIP, 50 mg/kg.d, ipx8d) significantly increased the weight of spleen and number of white blood cell and lymphocyte in peripheral blood in normal ICR mice, and antagonized the immunosuppressive actions of hydrocortisone. There were marked potentiating effects on delayed hypersensitivity reaction induced by 2, 4-dinitrochlorobenzene in normal NIH mice treated with indigo plant as well as in immunodepressed mice induced by cyclophosphamide. By administration of IIP, the percentage of ANAE+ lymphocytes stained with acid alpha-naphthyl acetate esterase method were significantly increased in peripheral blood of normal ICR mice, and the decreases in number of ANAE+ lymphocytes in mice induced by hydrocortisone were prevented to a certain extent. But indigo plant root polysaccharide could not enhance Con A-induced lymphocyte proliferation of C57BL mouse spleen cells in vitro measured with MTT colorimetric assay. In addition, the plaque forming cells in 5 x 10(6) splenocytes of NIH mice treated with IIP were higher than that of the control group (P less than 0.01). IIP could also elevate the clearance rate of intra-venous charcoal particles in normal mice, i.e., stimulated the phagocytic activity of macrophages. The result indicates that indigo plant root polysaccharide is capable of increasing humoral and cellular immune functions and enhancing the functions of reticuloendothelial system, and might be a good immunopotentiator.

Applied topically on mucous membranes for cold sores -- indigo plus borneol (Bing Pian - ice slice)