Abstract:To make full use of walnut by-products，this study used an ultrasonic-assisted ethanol extraction of active components of Diaphragma juglandis Fructus.The antioxidant activities of ethanolic extracts of Diaphragma juglandis Fructus at varying concentrations and four different polar solvent extracts were evaluated using DPPH free radical scavenging ability and total phenol and flavonoid content.The scavenging ability of ABTS+radicals and hydroxyl radicals of n-butanol extract were measured.The effects of this extract on the oxidative stability of rapeseed oil was investigated using rapeseed oil as the substrate.The 60%ethanol extract of Diaphragma juglandis Fructus had higher antioxidant activity and the stronger antioxidant activity substances were mainly concentrated in the n-butanol extract phase.The IC50value of DPPH and ABTS+free radical scavenging ability of n-butanol extract was 0.010 mg/mL.The order of oil oxidative stability was as follows:0.02% tert-butyl hydroquinone>0.05%n-butanol extract>0.04%n-butanol extract>0.03%n-butanol extract>0.02%VC>0.02%n-butanol extract>0.01%n-butanol extract>control.The antioxidant activity of the oil with the addition of 0.04%n-butanol extract was comparable to oil with the addition of 0.02%VC.The results indicated Diaphragma juglandis Fructus extract had impressive antioxidant activity and could be used as a natural antioxidant active substance.