Antioxidant Activity and Compounds Identification of Kernels, Leaves and Pollen of Walnut(Juglandaceae)

In order to comprehensively develop walnut biological resources,the antioxidant activities of different walnut kernels,leaves and pollen extracted by 7 kinds of solvents were studied,and the antioxidant compounds of them were analyzed. Antioxidant activities were determined by DPPH and ABTS⁺ free radical scavenging abilities and FRAP reducing ability. The total phenol and total flavonoids were determined. The antioxidant compounds of the samples were detected by high resolution mass spectrometer. The results showed that the extracts obtained by 60% acetone as solvent had higher antioxidant activity in 7 solvents. DPPH(IC₅₀=0.156 mg/mL)and ABTS⁺(IC₅₀=0.131 mg/mL)radical scavenging power and reducing power(62.17 mg V_C/g)in pecan leaves were stronger than those of other leaves. Determination of antioxidant activity in different parts of ‘Xilin 3’ walnut showed that the order of DPPH and ABTS⁺ free radical scavenging power and FRAP reducing power from strong to weak was:Pellicle > leaves > pollen > kernel > peeling kernel. A total of 17 antioxidant active compounds were identified from 60% acetone extracts of ‘Xilin 3’ pellicle and walnut leaves,KT-J02 walnut leaves,pecan leaves by LC-MS,including 9 phenols and 8 flavonoids. Quercetin and wogonin were common compounds in 4 test samples. For walnut leaves,13 compounds were identified in the pecan leaves,4 kinds of unique compounds,namely gallic acid,3-caffeoyl quinic acid,epicatechin gallate and p-coumaric acid. There was one compounds for each in ‘Xilin 3’ and KT-J02 leaves,gallic acid-4-O-β-D-glucopyranose and catechin,respectively. Six components were identified in pellicle,and one unique compound was ellagic acid.