The Antioxidant Activities, Flavonoids Contents Of Major Walnut Cultivars In Shaanxi

Walnut (Juglans regia L.) is a kind of deciduous tree in the family of Juglandaccae. It is aexcellent plant with edible, medicinal, ecological, and material functions, and it is a rareeconomy resource plant in the world. Walnut, belongs to4great nuts, is also the majorspecies of woody oil-bearing plants in China. In this article, we analyse the contents and kindsof flavonoids in12cultivars in shaanxi. We use response surface analysis methodology (RSM)to optimize the extraction process of flavonoids, analyze the influences of different tissuesand treatments on the flavonoids contents. then we use DPPH free radical scavenging activityand Prussian blue method to research its antioxidant activities. The results are as follows:(1)Two RSM methods, CCD and BBD, are used to optimize the hot reflux and ultrasonicextraction process of flavonoids from walnut fresh leaves and green husk respectively. Thefront result shows that the ethanol volume fraction62%, liquid/solid ratio44.7:1, extractingtime5.2h, extraction temperature61℃, on this condition the yield of flavonoids is3.607%;the latter results shows that the ethanol volume fraction62%, ultrasonic temperature51℃,ultrasonic time31min, standing time6.5min, with this understanding the yield of flavonoidsis1.077%. By using different extracting methods with same sample, the result shows that thehot reflux process is better.(2)There are significant differences on flavonoids contents in different varieties and withdifferent treatments. To compare different treatments, the flavonoids contents of air-driedsamples are significantly higher than baked and fresh samples. The variability of flavonoidscontents are along with the changes of varieties and the tissues. Among air-dried samples inorder, the content of flavonoids for4-year old varities, the Wen185> MK>Vina> Luguang>Xiangling>Lvling. The difference between Lvling and Xiangling is not significant. For2-year old varities, Qingxiang>Liao4>Daixiang>Liao6>Luguang>Liao3>Liao1. Amongthe tissues in order, Green husk>diaphragma> leaves> petiole> branche> kernel, there isno significant difference between the content of branche and kernel.(3)The results of Favonoids antioxidant activity shows that the clearing DPPH activity ofdifferent tissues from strong to weak, in order: kernel>diaphragma>branch> leaf> greenhusk. The EC50of them in their proper order are:0.0348,0.0496,0.182,0.212,0.307μg/mL. And the EC50of VC, quercetin, rutin, BHT are0.432μg/mL,3.709μg/mL,4.652μg/mL,6.552μg/mL, the ability of walnut flavonoids scavenging DPPH· is stronger than the fourkinds of antioxidants. Prussian blue reduction measurement shows that the reduction abilitiesof flavonoids of walnut are stronger than the antioxidants at the same concentration. Bothresults are consistent, show that walnut flavonoids have stronger antioxidant activity.(4)Chemical color test according to the results of flavonoids in different varieties andtissues are similar, but there are also differences. The walnut flavonoids consist mostly offavone, flavonol and flavanone. Maybe there are ketone compounds in green husk and nuts.