Extraction,Purification And Antioxidant Activity Of Flavonoids From Laurel Leaves

The root,stem,leaves and flower of Laurel have different medicinal value and physiological function.Laurel leaves contain a variety of bioactive substances,and the content of flavonoids is high.Flavonoids are a kind of natural extracts with anti-oxidation,anti-inflammatory and anti-cancer effects,and have broad prospects for development.At present,the research on flavonoids of Laurel leaves is focused on extraction conditions optimization.In this paper,the ultrasonic extraction,separation and purification,structural identification and in vitro antioxidant activity of flavonoids from Laurel leaves were studied systematically.NaNO2-Al(NO3)3 colorimetric method was used to determine the content of flavonoids in Laurel leaves.The UV-Vis absorbance was measured at 510nm after mixing the rutin standard,the crude extract of Laurel leaves and various color-developing agents.The rutoside standard curve was y=0.13046x+0.1261,R2=0.99884.The extraction process of flavonoids from Laurel leaves was optimized by single factor experiment and the response surface Box-Behnken method center combination.The optimum conditions of flavonoids were obtained:ethanol concentration 77%,temperature 55℃,time 36min,ratio of material to liquid 1:27.Under the optimum conditions,the extraction rate of flavonoids in Laurel leaves was 17.28%.The crude extract of flavonoids were seperated and purified by AB-8 macroporous adsorption resin,and eluted with different concentration of ethanol solution.After the combination of the same fractions,use the dextran gel Sephadex-LH20 to seperate,finally two flavonoids were obtained.The results showed that the flavonoid monomers from the leaves of Laurel were rutin and quercetin,identified by IR,UV-Vis,ESI-MS and NMR.Determine the in vitro antioxidant activity of crude extract,30%and 50%ethanol components of AB-8 macroporous resin,including the elimination ability of hydroxyl radical(·OH),DPPH free radical and total reducing power activity.It was found that the total reducing power of flavonoids in Laurel leaves was stronger than that of Vc,and had certain hydroxyl radical and DPPH radical scavenging ability,the DPPH free radical scavenging rate was up to 90%.