Chemical Constituents And Evaluation Of Free Radical Scavenging Activity Of Essential Oil From Piper Longum.L.

Piper longum L.is a plant of the genus Piperaceae,Also known as Piper Long,Bibo,Smilax,etc.it is widely grown in Indonesia,the Philippines,Vietnam and other places.The domestic main production is from Yunnan,Guangxi,Guangdong and Fujian.The essential oil of Piper longum L(EOPL)is the main active ingredients of Piper longum,which has the effects of anti-gastric ulcer,anti-oxidation,immune regulation,lowering blood fat,preventing,and treating gallstones.At present,there are many researches on Piper longum alkaloids at home and abroad,but the research on EOPL is not deep enough.Therefore,in order to make full and effective use of Piper longum resources,it is necessary to conduct further research on EOPL.This paper studies the extraction,antioxidant activity,microcapsule inclusions,and antioxidant applications of EOPL,and provides a theoretical basis for its application in the food industry.The research includes three parts:(1)Microwave-assisted extraction of EOPL and evaluation of antioxidant activity.Firstly,the yield of EOPL in the microwave crushing stage was studied and a single factor experiment(including the three factors of microwave crushing temperature,microwave time,and microwave power)was designed to determine the optimal range of extraction conditions.The response surface method was used to optimize the crushing and use response surface method to do crushing and get microwave assistance.The best process conditions for breaking the cell wall of Piper longum.Secondly,the extraction of EOPL was studied on the basis of microwave breaking.The influences of the ratio of material to liquid and power on the yield of EOPL were discussed.The results show that the best conditions for microwave crushing were:microwave temperature 96℃,crushing time 240s,and crushing power 700 W.When the power was 500 W and the material-to-liquid ratio was 1:10,the yield of EOPL was 0.55%.At the same time,the total antioxidant capacities and the activities of scavenging DPPH,ABTS~+,and OH free radicals of EOPL were studied and compared with synthetic antioxidants PG and BHT.The experiments show that within a certain concentration range,EOPL has good antioxidant activity,and its ability to scavenge OH free radical is stronger than PG and BHT.(2)Rapid screening of scavenging free radical active components from EOPL.For the first time in this subject,the chemical composition of EOPL was quickly analyzed by ultra fast gas chromatography electronic nose(GC-E-nose)technology and compared with the results of GC-MS.GC-E-nose combined with chemical method was used to screen activities of scavenging DPPH,ABTS~+,and OH free radicals of every component of EOPL and then their antioxidant reaction mechanisms were discussed based on the structural analysis.The relationship between the chemical structure and antioxidant activity was established.The results show that 35 chemical components of EOPL were identified by GC-E-nose and 39 components by GC-MS.Compared with the two detection results,the agreement was as high as 89.7%.The main components of EOPL are big root myrcene(26.04%),caryophyllene(13.57%),cis-anethole(8.87%)andβ-bisabolene(7.32%).cis-Anethole,oxycaryophyllene,and dextroterpene diene have the strongest scavenging activity against DPPH,ABTS~+,and OH free radicals with scavenging rates of 78.1%,87.0%and 71.6%,respectively.(3)The preparation of starch sodium octenyl sussinate(SSOS)including EOPL microcapsule(EOPL-SSOS)and its application in rapeseed oil.Because EOPL is uns Table and volatile at room temperature,the stability of EOPL was improved by use of formation of EOPL-SSOS.The preparation condition of EOPL-SSOSwas discussed.Furthermore,the microcapsule was added into rapeseed oil to study the changes in peroxide value(POV)and acid value under different treatment methods.The results show that:solid content of 40%,essential oil concentration of 60%,homogenization time of 5 min,and core-to-wall ratio of1:3 were the best conditions for forming microcapsule emulsions.EOPL and its microcapsule were added to rapeseed oil and stored in a constant temperature oven at 60℃.The results show that the POV of rapeseed oil treated with EOPL-SSOS was 58.79%～81.21%lower than that of untreated rapeseed oil,the acid value increase was less than39.70%～46.67%,which means that EOPL was embedded in SSOS and was not volatile.At the same time,the microcapsule can effectively inhibit the oxidative deterioration of rapeseed oil.The greater the amount,the higher the degree of inhibition,and the microcapsule showed better antioxidant effects,which can prolong the storage time of rapeseed oil.