Study On The Extraction And Separation Of Alliin From Allium Sativum L.

Allium sativum L. is a liliaceous plant which has various biological activities, it is effective in the prevention and treatment of cardiovascular diseases and cancers. Alliin is the precursor of Allicin (main biological active component in garlic) which widely exists in the cytoplasm of fresh garlic. Alliin is stable in usual environment, when the cytomembrane of garlic breaks due to the external force, alliin will react with alliinase and allicin will be formed. The latter will be oxidized or degraded in one hour even under normal atmospheric temperature and lose its biological activities. The author studied the extraction, separation, purification, the physicochemical properties determination and stability of alliin.Firstly, the HPLC method for alliin analyzing was determined: methanol: phosphate buffer (pH=5) =5:95 was selected as mobile phase, detection wavelength was 195 nm, flow velocity was 1 mL/min, sample volume was 20μL. The content of alliin in garlic from different areas was investigated using this method, the content of alliin is from 0.7% to 1.3%. Garlic from Jimusaer (Xinjiang Province), Dali (Yunnan Province) and Majiang (Guizhou Province) were the highest.Secondly, the pretreatment of garlic and the extraction of alliin were studied. Microwave technology was used to deactivate the alliinase, the lipid in the garlic was obtained by ethyl acetate in order to simplify the separation. Alliin was extracted using water as extracting solvent. The optimal conditions were confirmed by experiments via single factor and response surface methodology: Microwave power 750 w, Microwave time 90 s; Using water as extracting solvent, solid-liquid ratio is 1:5 (w/v) , temperature is controlled at 32℃and extracting time is 70 min. Under the optimal conditions, the extracting efficiency was 92.85±0.63%, the yield rate was 0.86 g/100 g.Thirdly, the separation and purification of alliin was studied. Alliin was absorbed by 732 cation exchange resin, the concentration of sample solution was 3 mg/mL, pH=2, the flow velocity of sample solution was 1 BV/h, the adsorption capacity was 900 mg/100 g wet resin. The eluting solution was ammonia water and its concentration was 0.25 mol/L, the eluting flow velocity was 1 BV/h. The purity and recovery rate of alliin were 64.5±2.0% and 81.8±1.9%, respectively. Then, this crude alliin-containing product was dissolved by water and crystallized by ethnal for three times. After the purification, the purity and recovery rate of alliin were 90.8±1.7% and 63.5±2.4%, respectively.The melting point of alliin was verified by Thermogravimetric and Differential Scanning Calorimetry technology and both of them were 163.5℃. The chemical constitution of alliin ending product was verified by Ultraviolet Spectrum and Infrared Spectrum. High Performance Liquid Chromatography coupled Mass Spectrum showed the molecular weight of alliin was 177.22 dalton, matched that of allicin described in the relative references. The stability of alliin solution in different temperature was studied and the results showed the loss rates of alliin were 0.6% in 50℃for 8 hours and 23.1% in 90℃for 8 hours, respectively.