Study On Antioxidant Capacities And Extraction Of Phenolic Compounds Of Perilla Frutescens By Microwave-assisted Methods

Perilla frutescens is a dual-purpose plant which can be used for food and medicine.It can be applied in many aspects such as natural spices,chemical raw materials, pharmaceutical raw materials,food ingredients,bio-pesticides and other aspects. Rosemarinic acid is the main phenolic constituent and an important functional component in Perilla.This paper mainly studied the optimization extraction of polyphenols from Perilla leaves using microwave and its antioxidants capability.It also studied the influence on the extraction of phenolic constituents-rosmarinic acid,caffeic acid,total flavonoids, total polyphenols,antioxidant capacity and their correlation after different methods of pretreatment of Perilla leaves.Then it studied rosmarinic acid,caffeic acid,flavonoids and antioxidant capacity in different parts of the Perilla.It aims at providing reference for the development and utilization of Perilla raw materials,especially for the extraction of rosmarinic acid.The major findings were presented as follows:1 This paper studied the influence of factors of organic solvent concentration, microwave power,microwave extraction time,liquid/solid ratio on the extraction rate of Perilla leaf polyphenols and its antioxidant capacity using microwave by single-factor experiments.On the basis of single-factor experiments,using Box-Benhnken experimental design principle,it optimized the microwave extraction of polyphenols through the response surface analysis method.As an indicator of total phenolics,the model obtained produced a satisfactory fitting of the experimental data with regard to total polyphenol extraction(R~2=0.97,P＜0.01).The optimum conditions were as follows:Volume concentration of 41%ethanol,microwave time of 104s,microwave power of 271W.Under these conditions,Perilla leaf polyphenols extraction rate was 15.86mg/g DW on theory. The actual extraction rate was 15.74mg/g DW.It showed the reliability of the model.2 This paper studied the influence on rosmarinic acid,caffeic acid,total flavonoids,total phenolic content and FRAP,DPPH antioxidant capacity after different pretreatments of Perilla leaves(P＜0.01),as well as the correlation between these indexes.The results were as follows:Five pretreatments of raw materials included the control,the shredded,the grinded,the 60℃dried,the dried by sun.And the Shredded leaves had the highest contents of rosmarinic acid,caffeic acid,total flavonoids,total phenolics and FRAP,DPPH antioxidant capacity.There were 4.37mg/g FW,0.09 mg/g FW,3.70 mg/g FW,12.36 mg/g FW,22.44 mg/g FW,4.54 mg/g FW respecively.After the treatment of grinding,60℃drying,and sun drying,rosmarinic acid content decreased most significantly,followed by flavonoids.Correspondingly,the total phenol content and antioxidant capacity reduced significantly.While the content of caffeic acid showed the opposite principle.The grinded treatment increased the content of caffeic acid.Correlation analysis showed that rosmarinic acid content,total phenolics,FRAP and DPPH had a significant correlation(P＜0.01).This indicated rosmarinic acid had high proportion in the total phenols in the Perilla and its strong antioxidant capacity.In addition,the results of the alkaline solution extracting phenolic compounds were as follows:Caffeic acid content was significantly increased.But no rosmarinic acid was detected in the experiment.3.This paper studied rosmarinic acid,caffeic acid,total flavonoids,total phenolic content and FRAP,DPPH antioxidant capacity of different parts(leaves,stems,roots)of Perilla frutescens.From the experimental results we could see that different parts(leaves, stems,roots) had significant differences on the content of rosmarinic acid,caffeic acid, total flavonoids,total phenolic,FRAP,DPPH antioxidant capacity(P＜0.01).Overall,In addition to caffeic acid,Perilla leaves had the highest concent of each component.The total phenolic acids and flavonoids content in the leaves were the highest,8.16mg/g FW, followed by the root,0.43mg/g FW.The stem had the lowest content of 0.19mg/g FW. The content of caffeic acid presented the different disciplines.Its content from high to low were as follows:root＞leaf＞stem.Caffeic acid contents are low in all parts and had a maximum content of 0.13mg/g FW.