Study On The Extraction And Antioxidant Activity Of Limonoids From Citrus Peel

In the experiment,four kinds of citrus peels—Citrus unshiu Marc,Citrus sinensis, Citrus grandis Osbeck,Citrus reticulate Blanco which are common in Sichuan—were taken as raw material.The main contents were as follows:Determination of main functional components from citrus peels and selecting the breed that the contents of limonoids were the highest to explore the technics;Observing the HPLC analysis method of limonin and nomilin;Studying on the degreasing and extraction process of limonin and nomilin;Comparing the contents of limonin and nomilin from four kinds of citrus peels which were extracted in optimum technics;Purefying elementarily limonin;Studying on the antioxidant activity of limonin and nomilin.The main results were as follows:(1) Determination of main functional components from citrus peelsThe contents of limonoids:Citrus unshiu Marc＞Citrus sinensis＞Citrus grandis Osbeck＞Citrus reticulate Blanco,selecting the Citrus unshiu Marc peels to explore the optimum techinics;The contents of flavonoids,TDF,IDF and total phenolic acids in Citrus sinensis peel were the higest;SDF,totle pectins and water soluble pectins in Citrus grandis Osbeck peel were the higest;The contents of carotenoids in Citrus reti -culate Blanco peel were the higest;The contents of different functional components in the same citrus peel also existed difference.(2) Observing the HPLC analysis method of limonin and nomilinObserving the selected chromatographic condition,the calibration curve was linear in the range of 7.2～225μg/mL for limonin(R²=0.999)and 6.18～193μg/mL for nomilin(R²=0.9993);the average recoveries were 95.73%(RSD=1.28) and 88.89% (RSD=2.08)respectively.The method possesses merits of good accuracy and reproducibility,so it might be used for the detection of limonin and nomilin.(3) Studying on the degreasing and extraction processWith the yields of limonin and nomilin as the indexes of surveying,some factors which influenced the yields such as degreasing or not,the method,the solvent and time of degreasing were observed,and the optimum technics was that the power was defeased by ligarine(60-90℃)in soxhlet's extractor at 40℃for 10h. With the yield of limonin and nomilin as the index of surveying,the best method of extraction was screened,the best solvent of extraction,the best reduction ratio of power,the appropriate range of time,tempreture and liquid-solid ratio were selected;the optimum technics for limonin and nominlin from citrus peels were determined by means of response surface method(RSM),and the results were as follows:the extration solvent was alcohol,the reduction ratio of power was 80 screen mesh,the time was 19.5h,the tempreture was 51.5℃and the liquid-solid ratio was 95ml:3g.Under the certain condition,the yields of limonin and nominin was up to 505.12μg/g and 111.74μg/g respectively.(4) Difference of contents and purefying elementarilyThe difference between limonin and nominin from the same citrus peel was significant,and the content of limonin was 2.4～15.5 times of that of nomilin.The contents of limonin:Citrus sinensis＞Citrus grandis Osbeck＞Citrus unshiu Marc＞Citrus reticulate Blanco,the contents of limonin from the Citrus sinensis peels were higer obviously than the three other breeds,and up to 935.29μg/g;the contents of nomilin:Citrus grandis Osbeck＞Citrus unshiu Marc＞Citrus sinensis＞Citrus reticulate Blanco.Based on an overall consideration,the crude extract from Citrus sinensis peels was used to purely elementarily.Through the HPLC qualitative and quantitative analy -sis,the main ingredient in the raw crystal was limonin and the content of limonin was 50.13%.(5) Studying on the antioxidant activityWith Vc and BHT as positive reference,the antioxidant activity of limonin and nomilin were determined by various assays,including reducing power,the effect of scavenging·OH,O₂^-·,DPPH radical.â‘ In the range of 25～200μg/mL,the results of reducing power showed:V_c＞the crude extract from Citrus sinensis peels＞BHT＞the raw crystal of limoninâ‘¡The effect of scavenging·OH,O₂^-·,DPPH radical:V_c＞the crude extract from Citrus sinensis peel＞BHT＞the raw crystal of limoninâ‘¢The reducing power and the effect of scavenging·OH,O₂^-·,DPPH radical of limonin and nomilin standard substance were weaker obviously than the crude extract and the raw crystal with the same concentration,but the antioxidant activity of limonin standard substance were higer slightly than that of nomilin standard substance.