Production Process of Qing Dai (Indigo Naturalis)

Production process of Qing Dai (Indigo Naturalis) involves traditional botanical extraction methods designed to isolate valuable bioactive compounds from indigo-producing plants. Used for centuries in traditional Asian medicine, this refined blue powder requires careful harvesting, natural fermentation, and precise purification to ensure therapeutic potency and safety.

1. Selection and Harvesting of Raw Botanical Materials

The manufacturing journey begins with selecting mature indigo-containing flora. Primary species include Polygonum tinctorium (Japanese indigo), Isatis tinctoria (woad), and Strobilanthes cusia. Workers harvest fully matured leaves and stems, thoroughly washing them to eliminate soil and organic impurities.

2. Aqueous Soaking, Fermentation, and Alkalinization

Once cleaned, fresh plant material is submerged in large water tanks for 24 to 48 hours. Natural microbial fermentation converts indican—a naturally occurring glycoside—into indoxyl.

Following fermentation, limewater (calcium hydroxide) is introduced to create an alkaline solution. Workers agitate the mixture to introduce oxygen, causing indoxyl to oxidize into insoluble indigo, which precipitates as a dense blue slurry at the tank bottom.

3. Collection, Purification, and Drying

After draining the liquid, producers collect the thick indigo sediment. This raw paste undergoes multiple washing cycles using clean water to remove excess lime, plant debris, and water-soluble contaminants. The purified paste is subsequently sun-dried or gently heat-dried before being milled into a fine powder.

4. Quality Refinement for Medical Applications

The production process of Qing Dai (Indigo Naturalis) yields a versatile compound used in traditional Chinese medicine, natural fabric dyes, and artistic pigments. When prepared for health applications, such as treating ulcerative colitis or psoriasis, manufacturers enforce rigorous quality control measures to verify purity.

Understanding the production process of Qing Dai (Indigo Naturalis) helps practitioners appreciate how traditional techniques preserve active compounds like indirubin for modern health solutions.