Resource efficiency and environmental impact of juglone in Pericarpium Juglandis: A review

Abstract

Black walnut (Juglans nigra) is considered one of the most valuable plants, with a global production of 3.5 million tons of dried fruit yearly. Throughout the past two millennia, its allelopathic effects have been widely recognized. Black walnuts produce a natural naphthoquinone called juglone, which occurs naturally in all parts of the tree, particularly the green husk, and contributes significantly to the allelopathic effects of black walnut. Except for the fruit’s edible nature, the walnut green husk (Pericarpium Juglandis) has been used for centuries to make wine, natural dyes, and traditional medicines to cure certain diseases. Within the extracts of walnut green husk, 1,4-naphthoquinones, gallic acid, caffeic acid, and quercitrin were separated and characterized. Among these compounds, the major active ingredient with a good application prospect is juglone, which has proven to be a natural chemical compound with anticancer, antitumor, antibacterial, and antiviral activities, especially the strong anticancer activity. Juglone is also an environmentally friendly biological pesticide and herbicide. Certainly, the environmental impact of juglone also needs to be considered. Significant quantities of walnut green husk are currently produced as a byproduct of walnut production; however, its value has not been fully utilized and explored, which raises environmental concerns. This review attempts to: 1) summarize the origin and historical use of walnut and walnut green husk; 2) introduce the structure, biosynthesis pathway, extraction method, biological activity, and potential applications of juglone, as well as its environmental impact assessment.

Walnut By-Products and Elderberry Extracts—Sustainable Alternatives for Human and Plant Health

“…Attempts are being made to replace fungicidal treatments that use synthetic, polluting chemical substances with more environmentally friendly plant extracts. Studies were carried out on extracts of the woody and green shells of walnuts, and their antifungal activity on cultivated plants, vegetables, and fruits was observed [ 90 , 91 , 92 ].…”

Exploring the Ecological Implications, Gastronomic Applications, and Nutritional and Therapeutic Potential of Juglans regia L. (Green Walnut): A Comprehensive Review

“…Supporting research and innovation in water quality and conservation, soil health, energy use, and air quality can help minimize the environmental impact of walnut production [ 97 ].…”

“…Antibacterial agent Application as a food additive Contributes to increasing soil carbon [78,79,90,91,118] Antitumor activities Preparation of bioactive packaging film and nano-chitosan coating Helps in reducing pollution [58,59,92,[95][96][97] Improves memory loss and protection of nerves Formulation of beverages Improves soil health [19,56,63,87,93,98,99] Anti-Obesity and hypoglycemia To improve product texture Acts as a natural insecticide [99][100][101][102] Neuroprotection Dietary fiber as a source of prebiotic Acts as a natural herbicide [64,103,104] Anti-inflammatory properties Food fortification Preparation of polymer composites [103,[105][106][107][108][109] Improves cells Confectionery applications Natural dye source [10,87,95,110] Prevention of chronic diseases Production of sugars Removal of hazardous materials [111][112][113][114][115][116]…”

Role of the Green Husks of Persian Walnut (Juglans regia L.)—A Review

“…Allelopathic compounds in husks serve as pesticides and herbicides [100,101]. It is also important to note that green husks are used in making wine, traditional liqueur, and jam [102,103], whereas green nuts are used in pharmaceuticals and cosmetics [81].…”