Zhu Dan

Zhu Dan is the dried bile or gallbladder of the domestic pig, Sus scrofa domestica L. (Suidae), obtained as a byproduct of slaughter. The fresh bile, a viscous green-yellow fluid stored in the gallbladder, is collected and either concentrated by evaporation to a dark brown extract (Zhu Dan Zhi) or the entire bile-filled gallbladder is dried whole. The substance contains conjugated bile acids (notably hyodeoxycholic and chenodeoxycholic acid), bile pigments (bilirubin, biliverdin), cholesterol, and phospholipids responsible for emulsifying fats and modulating intestinal flora. In traditional Chinese medicine, Zhu Dan is bitter, cold, and slightly toxic, entering the liver, gallbladder, lung, and large intestine channels; it clears heat, moistens dryness, resolves toxicity, transforms phlegm, and stops cough, used for cough with thick yellow phlegm, constipation from heat dryness, eye redness, jaundice, and topically for skin sores. It is an ingredient in classical formulas such as Dan Dao Pai Shi Tang and historically used to coat pills (Zhu Dan Zhi Wan).