A Comparative Review on the Extraction, Antioxidant Content and Antioxidant Potential of Different Parts of Walnut (Juglans regia L.) Fruit and Tree

Abstract

As a valuable tree nut, walnut is a well-known member of the Juglandaceae family. The fruit is made up of an outer green shell cover or husk, the middle shell which must be cracked to release the kernel, a thin layer known as skin or the seed coat, and finally, the kernel or meat. The nutritional importance of walnut fruit is ascribed to its kernel. The shell and husk are burned as fuel or discarded away as waste products. In the past two decades, the evaluation of the phenolic content and antioxidant activity of different parts of walnut has received great interest. In this contribution, the recent reports on the extraction and quantification of phenolic content from each part of the walnut tree and fruit using different solvents were highlighted and comparatively reviewed. The current review paper also tries to describe the antioxidant content of phenolic extracts obtained from different parts of the walnut tree and fruit. Additionally, the antioxidant and antiradical activities of the prepared extracts have also been discussed.

The Effects of Dietary Inclusion of Bilberry and Walnut Leaves in Laying Hens’ Diets on the Antioxidant Properties of Eggs

“…Walnut (Juglans regia L.) is considered a priority plant by the food and agriculture organization (FAO) and is a strategic species for human nutrition [8]. Walnut co/by-products, rich in phenolic compounds, are produced in agricultural industries and are a valuable source of antioxidants for animal nutrition.…”

Pomegranate Juice Extract Decreases Cisplatin Toxicity on Peripheral Blood Mononuclear Cells

“…In addition, the antioxidant activity of DPPH was more efficient with methanol than with ethanol. This antioxidant activity was 70% with methanol compared to 33% with ethanol knowing that methanol is more polar than ethanol and can extract more chemicals [ 18 ]. This was also observed by the transformation of violet color to yellow color as the concentration of DPPH was increased from 0.1 to 0.5 mg/mL.…”

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.…”

“…This part of the walnut fruit has not been comprehensively studied in comparison with those of other tree nuts. 30 The most critical and divergent antioxidants are concentrated in this part of the fruit and act as protective agents against harmful UV radiation effects, as well as microbial, fungal, and viral contamination.…”

“…It is crucial point is to reconsider the value of the husk and the shell, not as agricultural waste products to be generated and discharged into the environment during the production of the walnut kernel, but as valuable by-products with applications in the pharmaceutical, nutritional and industrial elds. 30…”