[Textual research on medicinal blue herbs]

Area of Science:

• Ethnobotany
• Traditional Chinese Medicine (TCM) History
• Pharmacognosy

Background:

• The historical usage of bluegrass as a medicinal herb has undergone significant transformations.
• Understanding these changes is crucial for accurate identification and application in modern herbal medicine.

Purpose of the Study:

• To systematically document the historical evolution of bluegrass (Isatis indigotica) concerning its nomenclature, geographical origin, and medicinal plant parts.
• To trace the changes in collection, processing, and preparation methods of bluegrass throughout different historical periods.

Main Methods:

• Comprehensive review of ancient herbals, medical texts, and prescriptions.
• Integration of findings with modern scientific literature.
• Systematic collation and verification of historical data.

Main Results:

• Bluegrass was initially used medicinally via its fruit (blueberry), originating from Polygonum tinctorium, but this practice declined after the Ming and Qing Dynasties.
• Medicinal use expanded to stems and leaves (Wei and Jin Dynasties), and later to roots (Song Dynasty), with 'Banlangen' emerging as a key term.
• Isatis indigotica roots became prominent by the Qing Dynasty, while Baphicacanthus cusia became known as southern indigo root. Clerodendrum cyrtophylum leaves were historically dominant but gradually replaced by Isatis indigotica and Polygonum tinctorium leaves.

Conclusions:

• The medicinal application and botanical sources of bluegrass have evolved considerably over Chinese history.
• The identification of medicinal parts and origins requires careful historical and botanical consideration to avoid confusion with contemporary uses.