[Persian Qing Dai: A Bibliographical Study]

The term "Persian Qīng Dài", first appeared in the Tang Dynasty, was used mainly for textiles-dyeing, eyebrows-darkening and hair-dyeing. It was also used as medicine orally taken for clearing heat, removing toxins, cooling blood and hemostasis. However, its botanical origin and its differences from native Qīng Dài have been debated for ages. This paper collated historical literature with ancient methods reduction and clarified the original plant, provenance and manufacturing process of Persian Qīng Dài. It was found that Persian Qīng Dài was, in fact, foreign indigo "flowers" derived from Indigofera tinctoria L. (wood-indigo), rather than from mactra clam powder or other sources. Indigofera tinctoria possesses distinct advantages as an indigo-yielding species; the indigo produced was superior to that obtained from the Chinese native plants Baphicacanthus cusia, Polygonum tinctorium and Isatis indigotica. Historical Persian Qīng Dài was probably introduced from India, where traditional indigo manufacture relied on Indigofera tinctoria and employed steeping and oxidation with little lime. It is recommended that Indigofera tinctoria be reinstated as a legitimate botanical source of Qīng Dài in the Pharmacopoeia of the People's Republic of China, and that Chinese production be improved by adopting the Indian steeping-oxidation process.