Study On Extraction,isolation And Purification Of Quebrachitol In Litchi

China is the largest producer of litchi and has a long cultivation history.The cultivated area is about 600 thousand hectares,and the yield is over 2 million tons,which account for 73.4%of the total litchi production area and 57.8%of the total litchi production in the world.There are lots of litchi wastes during the process of eating,processing and pruning such as pericarp,seeds,and branches.Currently these wastes have no good utilization ways.Previous studies have shown that litchi is rich in quebrachitol,and concentrations are similar to that of common rubber latex and in some tissues the concentrations are even higher.Thus,litchi is a good potential material for quebrachitol extraction and purification.In the present study,the contents of soluble metabolites in leaves,branches,flesh,seeds and pericarp of litchi were determined by GC-MS,and factors affecting the extraction rate of quebrachitol were explored after screening out the best tissue for quebrachitol extraction.During purification,we investigated the effect of decolorization and impurity substance removal in the extraction of quebrachitol from litchi by using activated carbon and C₁₈ column,and the microfiltration membrane was applied during isolation and purification effect.In the last step,methanol precipitation was applied and relative pure quebrachitol was obtained.The main results are as follows:1.The components and contents of major soluble metabolites in different tissues/organs of litchi were detected by gas chromatography mass spectrometry?GC-MS?.The contents of quebrachitol in litchi pericarp was the highest,but high phenolics,and the presence of myo-inositol and other methyl inositol make pericarp not an ideal material for quebrachitol extraction and purification.The branch of litchi contained relative high levels of quebrachitol,and the soluble sugar content was relatively low.And most importantly,there was no interference methyl inositol.Hence,the branch of litchi is an ideal material for quebrachitol extraction and purification.2.High performance liquid chromatography?HPLC?detection was used to compare the contents of quebrachitol in the pericarp,seed and branch with different drying methods.There showed minimal difference in contents of quebrachitol in the oven-dried and freeze-dried samples,which indicated that both drying methods could be used for the pretreatment of the quebrachitol extraction materials.Among the branches of the 5 common litchi varieties,the order of the contents of quebrachitol detected from high to low are'Feizixiao'>'Huaizhi'>'Guiwei'>'Nuomici'>'Heiye'.3.Since the most abundant litchi branch samples obtained in this study are from cultivar'Heiye','Heiye'branches are then used as main materials to screen out the best single factor in the extraction process by determining the quebrachitol contents of different extraction programmes using high performance liquid chromatography.The best single factors in quebrachitol extraction were:the branch partical size 40-60 mesh;extraction temperature of 80?;45%ethanol extract solution;1:10 material to liquid ratio;60 min extraction time;80%ultrasonic power?total power 600W?.These are the best the extraction conditions for quebrachitol extraction in the branches of litchi.4.The decolorization treatment plays an important role in the final crystals of the quebrachitol.We used activated carbon and C₁₈ column as the main decoloring agent in the present study.Data showed that the activated carbon reduce quebrachitol contents of branch extration.The activated carbon amount around 6%displayed good decolor effects and have less reduction of the quebrachitol contents as comparing with the initial extract solution.C₁₈ column meet the the decolorization requirment,and there is no obvious reduction of quebrachitol.5.The microfiltration membrane was used as the main material for the purification of quebrachitol in this experiment.After pretreatment,the solution filtered by the microfiltration membrane displayed higher light transmittance than the unfiltered solution,but the microfiltration membrane had a certain degree of quebrachitol adsorption for decreases in quebrachitol content after pass through the microfiltration membrane.6.In the methanol precipitation and crystallization experiment,it was found that the polysaccharides and sucrose in the sample were precipitation with quebrachitol.The use of hydrochloric acid can effectively remove polysaccharides and sucrose on the sedimentation and crystallization.Relatively pure quebrachitol can be obtain after acid hydrolysis and repetitious methanol precipitation.