Influence of environmental factors on antioxidant activity, phenol and flavonoids contents of walnut (Juglans regia L.) green husks

Abstract

Antioxidant activities of methanol extract of walnut green husks (Juglans regia L.) from 11 regions of Iran with the different geographical and climatic conditions were measured. The phenolic and flavonoid contents of extracts were also evaluated. The antioxidant activities were evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, nitric oxide scavenging and reducing power ability. Antioxidant activity has been compared with BHA, quercetin and vitamin C. All extracts were weaker than standards. The Chogholondi sample was found to have the better antioxidant activities in scavenging DPPH radicals however; Chino sample has better nitric oxide scavenging activity than others. The good correlation coefficient was existed between the phenolic and flavonoid contents with collection altitudes. Total phenolic contents were ranged from 15.15 to 108.11 mg gallic acid equivalents g-1 of extract and the flavonoid contents varied from 3.59 to 22.91 mg quercetin equivalents g-1 of extract. Among all extracts analyzed, Abali sample exhibited a significantly higher phenolic and flavonoid content than samples (p < 0.05).   Key words: Juglans regia L., antioxidant activity, phenol, flavonoid contents, walnut, green husks, 1,1-diphenyl-2-picrylhydrazyl.