| In the study,phenolics content of walnut(Juglans sigillata Dode.cv.‘Qianhe-5',‘Qianhe-6',‘Qianhe-7',and ‘Qianhe-8')were analyzed in different cultivars,different organs,and different developmental stages.The antioxidant activities and enzyme activities related phenolics metabolism during leaves and fruits development were also studied in order to confirm the relationship between phenolics content and antioxidant activity or metabolic enzymes activity,which can provide a theoretical basis for further clarity mechanism of phenolics biosynthesis.The results are as follows:1.Significant differences of total phenolics content and phenolic compounds were found among varieties.‘Qianhe-6' had the highest contents of total phenolics and total flavoniods,while the lowest in ‘Qianhe-7'.There are no differences in phenolic compounds types,but their contents were different among varieties.Leaves of ‘Qianhe-6' contained the highest or higher contents of total phenolics and phenolic compounds,such as chlorogenic acid and rutin.On the other hand,‘Qianhe-7' contained the highest contents of catechin,caffeic acid,and juglone,although the total phenolic content was the lowest.Similarly,kernels of ‘Qianhe-6' contained the hightest contents of phenolic compounds,except ferulic acid and quercetin,while the contents of catechin,caffeic acid,and ferulic acid were at the lowest in ‘Qianhe-7'.Not only the contents of phenolic compounds,but also the types of phenolic compounds were different in green husks and pellicle among varieties.Vanillic acid was only detected in the green husks of ‘Qianhe-7' and epicatechin only in ‘Qianhe-6',juglone only in the pellicle of ‘Qianhe-7'.2.Significant differences of total phenolics content and phenolic compounds were found among organs.Total phenolics content in descending order were as follow: pellicle,roots,leaves,branches,inflorescences,green husks,and kernels in ‘Qianhe-7',but leaves higher than roots in ‘Qianhe-6'.Thirteen kinds of phenolic compounds were identified in leaves and green husks,eleven in branches,roots,and inflorescences,ten in pellicle,and six in kernels.Rutin was observed at the highest content in both of leaves and pellicle,while juglone was a dominanted phenolic compounds in green husks,branches,roots,and inflorescences,but the contents in these organs were different.Only six phenolic compounds were founded in kernels,and they were all in lower contents.3.Significant differences of total phenolics and phenolic compounds contents were found in different organs during developmental stages.The results showed that total phenolics content presented a trend of bimodal curve during the annual growing period in leaves.It changed differently in green husks,total phenolics content declined first,then increased,and declined again.While in both kernels and pellicle,total phenolics content increased first,then trend to stable,and increased again.Most of phenolic compounds decreased in fruit enlargement stage,and increased in kernel-filling period in both leaves and green husks.Except juglone reached the peak in kernel-filling period in pellicle,the other kinds of phenolic compounds showed upward trends,and reached the highest peak at mature stage in pellicle.While irregular variation of phenolic compounds content were found in kernels.4.Antioxidant activities of different organs in a descending order were as follows: pellicle,leaves,green husks,and kernels,they all changed regularly with the development.Leaves showed lower antioxidant activity in blooming and fruits setting stage,but higher in kernel-filling period and fruits maturation period.Antioxidant activity of green husks was higher in young fruit period,and undulated slightly in the rest of seasons,when another peak was found in early kernel-filling period.Both antioxidant activities of pellicle and kernels showed upward trend with fruits maturing.5.Enzymatic activities of phenolics biosynthesis were difference between leaves and fruits during developmental stages,and high enzyme activities lead to higher phenolics content.Young leaves showed higher enzyme activities and went up again in hardcore or kernel-filling period except 4CL,On the contrary,green husks showed lower enzyme activities in young fruits stage and rose rapidly in late fruit enlargement period except 4CL.In pellicle,DAHPS,CS,and CM showed higher activities at early and later period of pellicle development,PAL activity showed a rising trend during the whole growing seasons,but downward trend of C4 H and 4CL activities were found in the study.In addition,CHS and CHI activities increased first and reached the peaks in kernel-filling period,then declined during the later growing seasons.In kernels,PAL,C4 H,CS,and CM activities increased first,then declined and reached the peaks in kernel-filling period,C4 H activity rose rapidly at mature stage.4CL,CHS,and CHI activities in kernels showed downtrend during the whole growing seasons,but recovered slightly at mature stage.POD and PPO activities showed a three-peak curve in leaves,W-shaped curve in green husks,but it declined first and went up at mature stage in pellicle during the whole growing seasons.POD and PPO activities were not detected in kernel.6.Both total phenolics and total flavones contents strongly correlated with antioxidant activity,while there were lower correlations between phenolic compounds content and antioxidant activities compared with totals.Their contributions to antioxidant activity are difference due to different organs,and gallic acid,rutin,and caffeic acid contributed greatly to the antioxidant activity.7.Correlations between different enzyme activities and total phenolics content or phenolic compounds content were difference,as well as the correlations between total phenolics,the same phenolic compound and the same enzyme activity in different organs.There was no obvious correlation between total phenolics content and enzyme activities of shikimic acid biosynthesis pathway,between total phenolics content and enzyme activities of phenylpropaniod biosynthesis pathway,but positive correlations were found between total phenolics content and enzyme activities of phenolics oxidation pathway.Most of phenolic acids and flavonoids content highly correlated with PAL,C4 H,and 4CL,moreover,flavonoids contents are highly correlated with CHS and CHI activities in leaves.All phenolic compounds content positively correlated with PAL activity in kernels and pellicle,gallic acid and rutin contents significantly correlated with PAL activity in pellicle,catechin content significantly correlated with CHS and CHI activities in kernels,respectively.No obvious correlations were founded between phenolic compounds content and enzyme activities in green husks. |
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