ACE Inhibitory Activity, DPPH Radical Scavenging Activity, and Metabolite Profiling of Extract and Fractions from Castanea crenata’s Inner Shell

Castanea crenata, also known as the Korean chestnut, is a species of chestnut tree native to Korea, Japan, and China. The C. crenata inner shell has long been used in oriental medicine and as a cosmetic in Asia. C. crenata exhibits curative properties, including antioxidant, anti-cancer, anti-inflammatory, and anti-wrinkle/firming effects. C. crenata inner shell tea is often enjoyed for its nutty, slightly sweet flavor and purported health benefits. This study evaluates the angiotensin converting enzyme (ACE) inhibitory and 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activities and metabolites of the C. crenata inner shell, a novel and excellent functional tea material. The ACE inhibitory activity and DPPH radical scavenging activity of various fractions obtained from the methanol extract of the C. crenata inner shell were evaluated, and the relatively highly polar EtOAc, n-BuOH, and H2O fractions showed high activities. Metabolite analysis was performed on the methanol extract and the fractions obtained from the C. crenata inner shell by using UPLC-ESI-QTOF-MS. In the LC-MS chromatogram of the MeOH extract of the C. crenata inner shell, 71 peaks were identified, including gallic acid, protocatechuic acid, ellagic acid, sugar alcohol, and sucrose. The results demonstrate the potential use of the C. crenata inner shell and its fractions as functional tea materials for beneficial health effects, including ACE inhibition and free radical scavenging.