Study On Extraction Of Tea Polyphenols From Fresh Tea Leaves Via Liquid Netrogen Processing And Its Lowering Plasma Cholesterol Function

In this paper, tea polyphenols (TP) extracted from fresh tea leaves via liquid nitrogenprocessing showed better stability and higher yield. Through the study of single factorexperiments and the orthogonal experiment design, the processing conditions for teapolyphenols extract via liquid nitrogen processing were optimized. Compared with thetraditional water extraction method, the content of catechins of tea polyphenol extract vialiquid netrogen processing was analysed by using HPLC. The UV method was confirmed todetect three kinds of bile salts in vitro. The binding capacity of bile salts of the two kinds oftea polyphenol extracts were studied as well as the correlation between tea functionalcomponents (TP) and the bile salts binding capability in vitro under the conditions of thesimulated human digestive environment. The bile salts binding mechanism of catechinsfunctional components including EC, EGC, ECG and EGCG was preliminary concluded viathe analysis of related factors.By varying extraction temperature, extraction time, solid-liquid ratio and extractionsolvent, experiments were conducted to study the extraction yield of the effectivecomponents-tea polyphenols in fresh tea leaves extract during extraction via liquid nitrogenprocessing. The results show that ethyl acetate was the best extraction solvent and theextraction yield of tea polyphenols was affected by extraction time, solid-liquid ratio andextraction temperature. Through the study of single factor experiments and the orthogonalexperiment design, the processing conditions for stirring extraction via liquid netrogenprocessing were optimized as the1:35solid-liquid ratio,5°C extraction temperature andextraction time was2min.Compared with the traditional water extraction method, the content of catechins of teapolyphenol extract via liquid netrogen processing was higher. The tea polyphenol, catechinsand esterified catechins contents were respectively improved by0.98%,6.08%and4.01%forthe liquid nitrogen processing. The content of catechin and esterified catechins via liquidnitrogen processing was190.93±0.1mg/g,98.38±0.06mg/g respectively. The properties oflowering temperature and isolating oxygen of liquid nitrogen were found beneficial toincrease the extraction yield of tea polyphenols, catechin and esterified catechins.UV detecion method shows perfect repeatability and stability between bile salt content and absorbance with R2of the standard curves were0.9993for sodium cholate (SC),0.9977for glychocholic acid sodium salts (SGC) and0.9989for sodium taurocholate (STC). Thebinding capacity of bile salts of the two kinds of tea polyphenol extracts were compared invitro under the conditions of the simulated human digestive environment. The result showsthat the tea polyphenol extract via liquid netrogen processing had binding capacity of bilesalts1.17±0.04μmol/mL TE for STC,1.11±0.02μmol/mL TE for SGC and0.99±0.02μmol/mL TE for SC. The result also proves that the content of tea polyphenolshowed bile salts binding capacity with a correlation coefficient higher than0.9232,indicating there was a significant correlation between bile salt binding capacity and teapolyphenol content.This study confirms clearly that the EGCG, EC, ECG and ECG showed significant bilesalts binding capacity in vitro. It could be concluded that catechins might play a major effecton the binding reaction in vitro. The reactions between bile salts and EGCG could be welldescribed by Freundilich adsorbtion isotherm, Langmiur adsorbtion isotherm and Tempkinadsorbtion isotherm with their correlation coefficient r all higher than0.97.