A Comprehensive Review of Traditional Chinese Medicine Ejiao (Colla Corii Asini): Chemical Composition, Quality Control, and Pharmacological Actions

Ejiao, derived from donkey-hide gelatine, is a traditional Chinese medicine with efficacy substantiated by contemporary pharmacological investigations. Chemically, Ejiao contains 19 amino acids, over 2000 peptides, 12 polysaccharides, over 100 volatile components, assorted trace elements, and fatty acids, contributing to its broad therapeutic potential. Quality control methods for Ejiao primarily involve high-performance liquid chromatography, chromatography-mass spectrometry hyphenation, DNA molecular identification, and nuclear magnetic resonance. Pharmacological studies have demonstrated Ejiao's blood-nourishing, anti-anaemic, lung-protective, anti-ageing, anti-fatigue, antioxidant, immune-modulating, anti-tumour, anti-osteoporotic, anti-Alzheimer, oestrogen-mimicking, and skin-repairing effects, with emerging applications in gastrointestinal and cardiovascular diseases. Future research should focus on elucidating its mechanisms of action, such as osteogenesis through Wnt/β-catenin and BMP/Smad pathways, antioxidative effects through Nrf2/HO-1 signalling, and immune modulation via cytokine regulation. Additionally, clinical trials and standardisation efforts are essential to optimise its therapeutic potential.