A Comprehensive Review on the Chemical Constituents and Functional Uses of Walnut (Juglans spp.) Husk

Abstract

The walnut (Juglans spp.) is an appreciated nut that belongs to the Juglandaceae family. The fruit includes four main parts: the kernel, the skin, the shell, and the green husk. It is widely cultivated due to its edible kernel. In walnut production centers, high amounts of the husk as an agro-forest waste product are produced and discarded away. Recently, it has been demonstrated that the walnut green husk could be valued as a source of different natural bioactive compounds with excellent antioxidant and antimicrobial properties. Regarding this respect, in this contribution, the current scientific knowledge on the antioxidant and antiradical activities, various identified and isolated individual chemical constituents, as well as the functional applications of the walnut husk with more emphasis on the Persian walnut (Juglans regia L.) are reviewed.

Recent advances in the use of walnut (Juglans regia L.) shell as a valuable plant-based bio-sorbent for the removal of hazardous materials

“…Recent investigations of these by-products demonstrated that they contain valuable compounds including phenolics. 6,[28][29][30] The green husk of the walnut fruit is available in high amounts. Recently, Oliveira, et al 31 recognized the aqueous extract of the low-cost green husk as an excellent natural source of phenolic compounds with antimicrobial and antiradical activities.…”

“…Aer its separation, the remaining part of the fruit is called the nut. 6 The woody and hard material that is the middle portion of the fruit is called the shell. In most walnut cultivars, the shell must be cracked mechanically to obtain the meat.…”

“…Unlike the kernel, the remaining parts of the fruit are regarded as waste products and are discarded without being put to any practical use. 6 Recently, the walnut shell has gained increasing attention due to its high availability and several unique properties. One of the main and recently highlighted applications of WS by-products is the use of processed or unprocessed WS as biosorbent.…”

Phytochemicals with Added Value from Morella and Myrica Species

“…Neuroprotective effects [32] 80% increase in N2a cells viability treated with 0. 84 Methanol extract of Myrica rubra (Lour.) Siebold and Zucc.…”

“…roots [19] Myresculoside (55 Methanol extract of Morella adenophora (Hance) J. Herb. roots [19] Myresculoside 55Molecules 2020, 25 * The stereochemistry was defined by Jahanban-Esfahlan et al [84]; ** The name was corrected based in the structure presented in the original paper since ursonic acid has a ketone group at C-3; The pharmacological potential of the compounds presented in Table 3 has not been evaluated so far by the researchers who have studied Morella and Myrica species. It should be noted that the isolation and structural elucidation are the first steps to describing the metabolomic profile of a species or genus, helping to assess their potential as a source of commercially valuable phytochemicals, adding value to the species, as well as finding alternative sources of pharmacologically active metabolites.…”