Treatment of atopic dermatitis with indigo naturalis or indigo producing plant extract

A method of treating an atopic dermatitis, comprising topically administering to a subject in need thereof, once or twice daily, a pharmaceutical composition comprising a solid extract of Indigo Naturalis and a pharmaceutically acceptable carrier,

• wherein the pharmaceutical composition comprises 0.01 to 10 mg of the solid extract per 1 g of the pharmaceutical composition, and
• the solid extract comprises, relative to the total weight of the extract:
• 65% to 90% (w/w) indirubin;
• 0.1-15% (w/w) indigo;
• and
• 0.01-5% (w/w) at least one of tryptanthrin and qingdainone.

A method of treating an atopic dermatitis, comprising administering to a subject in need thereof a pharmaceutical composition comprising a solid extract of Indigo Naturalis and a pharmaceutically acceptable carrier,

• wherein the solid extract is prepared from Indigo Naturalis by a process comprising:
• a) extracting the Indigo Naturalis or the plant with a solvent to obtain a mixture of extraction, wherein the solvent is selected from the group consisting of dimethylformamide, ethyl acetate, ethanol, dimethylsulfoxide, dichloromethane, tetrahydrofuran, dimethylacetamide, acetone, 2-butanone, acetonitrile, isopropyl acetate, 2-methyl tetrahydrofuran, methyl tert-butyl ether, methanol, chloroform, terpene, water and a combination thereof,
• b) filtering the mixture of extraction to obtain a filtrate,
• c) concentrating the filtrate to obtain a crude extract,
• d) mixing the crude extract with hexane or heptane to obtain a washing mixture, and
• e) filtering the washing mixture to obtain the solid extract.