Process optimization of tea polyphenols extraction from green tea by deep eutectic solvents and analysis of antioxidant activity
Deep eutectic solvents(DES)are widely used in biological and chemical fields as green,environmentally friendly,non-toxic and highly efficient solvents.In this study,deep eutectic solvents were used to extract polyphenols from green tea.Firstly,five different types of natural deep eutectic solvents were synthesized,and physical properties such as Fourier transform infrared spectroscopy(FT-IR)and viscosity values were characterized.Compared with extraction rates of tea polyphenols obtaining by using traditional water solution and 70%methanol organic solvent,the best DES type was acquired.Then,the single factor test and re-sponse surface Box-Behnken design test were used to opti-mize the extraction of green tea polyphenols based on DES,and the structure of green tea powder before and af-ter extraction was analyzed.The results showed that when the moisture content of choline chloride and lactic acid(DES-2)was 30%,extraction temperature was 75℃,extraction time was 29 min,and solid-liquid ratio was 1∶35(g/mL),the extraction rate of tea polyphenols was 25.16%,which was consistent with the prediction of the model.The results of scan-ning electron microscopy(SEM)and X-ray diffraction(XRD)showed that the crystal structure of tea powder did not change significantly during the extraction process,but the surface morphology of tea powder was changed greatly by DES,and more folds were formed on the surface of the tea powder,so that the tea powder had a larger contact area with the sol-vent,which was conducive to the dissolution of polyphenols.In addition,the DES extraction method was compared with the commonly used ultrasonic ethanol extraction method,microwave water extraction method,and hot reflux water extraction method.It was found that the DES extraction method had significant advantages in the extraction rates of tea polyphenols and some catechin components(P<0.05).The tea polyphenol extracts obtained by different extraction methods were tested for in vitro reducing power and 1,1-diphenyl-2-picrylhydrazyl(DPPH)free radical scavenging activity.It was found that the tea polyphenol extracts obtained by different methods showed antioxidant activity and the antioxidant activity was dose-dependent.The tea polyphenol extract obtained by DES method had the strongest antioxidant activity.The results of this study can provide a theoretical basis for the extraction and development of tea polyphenols.
deep eutectic solvents(DES)tea polyphenolsextraction technologyresponse surface methodolo-gyantioxidant activity
万方数据
维普
