Traditional Applications, Ethnopharmacology, and Phytochemistry of Walnut Green Husk (Juglans regia L.): A Review

Walnut green husk (WGH) is the immature exocarp of Juglans regia L., a famous traditional herbal medicine that has long been used in China, Korea, Iran, and other places for the treatment of psoriasis, baldness, type II diabetes mellitus, intestinal worms, promotion of wound healing, and other diseases. With the advancement of modern scientific research, many studies have identified that WGH contains quinones, diarylheptane, triterpenoids, and flavonoids, and has excellent antitumor, anti-inflammatory, antibacterial, and antioxidant properties. These findings support the ethnopharmacological application of WGH and highlight the need for further investigation of the plant's potential uses in pharmaceutical fields. In this article, we made a comprehensive review of the traditional applications, botany, chemical components, pharmacological effects, and factors affecting the therapeutic properties of WGH based on a scientific literature review with a view to provide the latest information and research direction for further study and potential use of WGH. All data are gathered from scientific databases including Google Scholar, Pubmed, Sci-Finder, Web of Science, ScienceDirect, and China National Knowledge Infrastructure.