Juglone Content in Leaf and Green Husk of Five Walnut (Juglans regia L.) Cultivars

Juglone (5-hydroxy-1,4-napthoquinone) is a chemical compound released by walnut trees that can be toxic for surrounding plant species. In the present study, juglone was identified in leaves and green husk in five walnut cultivars: Germisara, Jupanesti, Franquette, Vina, Valcor by using high performance liquid chromatography (HPLC-RP). Juglone was found predominant in green husk (average value of cultivars is about 31.308 mg/100 g). Significant differences in contents of identified juglone were observed among cultivars that ranged from 20.56 to 42.78 mg/100g for green husk, and 5.42 to 22.82 mg/100 g for leaves. It was also found that walnut green husk and leaves represent the most important source of walnut phenolics.