Internal Septum of Walnut Kernel: a Neglected Functional Food

Walnut (Juglans regia L.) is a well-known member of the Juglandaceae family and its kernel is widely consumed around the world for both unique nutritional characteristics and health-related benefits. Even though several studies investigated the composition and biological activities of different parts of the walnut tree, the internal septum of the walnut kernel is less evaluated. In the last two decades, some studies investigated phytochemical and pharmacological aspects of the walnut septum. Their results showed a wide range of biological properties along with safety of walnut septum constituents convincing us to shift our view to walnut septum as a useless by-product to a natural herbal material with valuable properties. The purpose of this review was to summarize the currently available investigations on chemical composition and biological activities of the walnut septum.  Several phytochemical studies showed that the walnut septum is a rich source of secondary metabolites like polyphenols are which estimated to be responsible for its high antioxidant property. Further experimental studies confirmed many biological activities of this by-product such as radical scavenging, food preservative, antibacterial, antitumor, hypoglycemic, hypolipidemic, and hepatorenal protective properties.