Anti-inflammatory activity of walnut (Juglans regia var. Sorrento) husk extract, chemical profiling and discovery of huskol, a new ursane-type triterpenoid

The study of potential high-added-value waste materials is pivotal for their recycling and repurpose in the market. Walnut husks are a well-known source of bioactive natural products with potential applications in the antimicrobial and anticancer therapies or in the cardiovascular and neurodegenerative prevention, and as anti- inflammatory treatments. However, since the metabolic content of walnut husks is highly dependent on their variety, there is still a need for thorough systematic phytochemical investigations of this precious waste material of the food industry. Herein we report the anti-inflammatory evaluation and an NMR-based phytochemical profiling of the ethyl acetate fraction of husks obtained from Juglans regia var. Sorrento. Our study demonstrated that the extract exerts significant anti-inflammatory activity by reducing the NO (IC50 = 0.01 mg/mL) and PGE2 (IC50 = 0.007 mg/mL) production in LPS-stimulated cells in a concentration-dependent manner by inhibiting iNOS and COX-2 proteins. The phytochemical analysis of the bioactive fraction revealed the dominant presence of diarylheptanoids and triterpenoids and resulted in the discovery of the new ursane derivative huskol.