Study On The Extraction And Separation Process Optimization Of Hops Polyphenols And Its Antibacterial Activity

Hops is a medicinal and edible plant which are rich in polyphenols, and used as liquor-making raw materials. Hops polyphenols is a kind of plant polyphenols. Researches indicated that plant polyphenols has the founctions of antitumor, antioxidation, antibacterial and eliminate the free radicals. Hops polyphenols used as food additive in order to prevent food from spoilaging, and it makes the hops polyphenols has a good commercial perspective. In this page, Marco Polo hops picked up from Yumen Yinma farm acting as the material. Based on the single factor experiment and orthogonal experiment, an optimal extraction process of hops polyphenols is confirmed. In addition, the separation process of hops polyphenols by the macroporous adsorption resin and the preliminary analysis of principle components by HPLC were studied. On the basis of above, the physicochemical properties and antibacterial activity were tested. The main results are as follows:1. Two extraction processes of polyphenols from compressed flake hops were studied, one was organic solvent reflux method and the other was microwave-assisted with the bath reflux method. The optimal extraction process of the organic solvent reflux method were: ethanol concentration 55%, bath time 3.5h, solid-liquid ratio 1:22 and bath temperature 78℃. Under that condition, the extraction rate of hops polyphenol were 2.387%. The optimal extraction process of the microwave-assisted and the bath reflux method were: microwave power 213W, microwave time 3.5min, ethanol concentration 63%,solid-liquid ratio1:15, bath temperature 92℃and bath time 25 min . Under that condition, the extraction rate of hops polyphenol 5.730%. The comparison of the microwave-assisted with the bath reflux and the organic solvent reflux method, the microwave-assisted with the bath reflux has obvious advantages, such as less time consumption, low energy consumption and high extraction yield that was as 2.4 times as the organic solvent extraction, it also has more suitable for extraction of polyphenols from hops.2. Six types of macroporous adsorption resin as filler for the separation and purification tests in hops polyphenol. Determined by static test in which X-5 resin most suitable for separation of polyphenols in hops, the optimum adsorption conditions of the dynamic adsorption experiment were: 0.6mg/mL feed concentration with flow rate of 1.5mL/min , the desorption solvent was 60% ethanol with flow velocity of 0.75mL /min. And the thermodynamic adsorption characteristics of hops polyphenols onto resin were studied. Results showed that adsorption equilibrium data obtained within the temperature range of 298～308 K and concentration range of 0.2～1.2 mg/mL could be well fitted by the Freundlich-type isotherm equations and the adsorption was favorable type. Meanwhile, the changes of entha hops polyphenols, free energy and entropy were measured. It was indicated that the adsorption was an exothermic process.3. Used Hops polyphenol extracts as HPLC external standard analysis the fine structure, though rutin, quercetin, kaempferol, epicatechin, catechin and gallic acid mix standard maps and standard curve, which obtained by the fine purification of hop polyphenols were mainly consisted of extracts of rutin, catechin and quercetin three types of phenolic compounds, and their contents were 1.438 mg/mL, 0.032 mg/mL, 0.012 mg/mL.4. The physical and chemical characteristics of hops polyphenols such as dissolubility, light refraction were determined primaryly. The results showed that the dissolubility of hops polyphenols in CH₃OH, CH₃CH₂OH, C₂H₅COOC₂H₅ were better than H₂O, CH₃Cl and C₂H₅OC₂H₅. Refractive index of hops polyphenols in different solvents was CH₃CH₂OH > C₂H₅COOC₂H₅ > CH₃OH > H₂O > CH₃COCH₃ > C₂H₅OC₂H₅ = CH₃Cl. Characteristic color reaction showed hops polyphenols had the commonness of phenols characteristic color reaction. Though HPLC external standard method using the composition of the rutin, quercetin and catechin in these three activities with six hydroxyl groups of phenolic biphenyl; and thus with the Folin phenol reagent, ferric chloride reaction also showed a blue purple and green, indicating that they have a phenolic hydroxyl group active substances.5. Hop polyphenols on the common cause of food spoilage micro-organisms in the inhibitory effect showed that the tested concentration of hop polyphenols 4mg/mL 1mg/mL range for Saccharomyces cerevisiae, Rhizopus, Mucor, Penicillium, black Aspergillus were no inhibitory effect, no inhibition zone; against Staphylococcus aureus, Escherichia coli, Bacillus subtilis, the three kinds of bacteria have antibacterial activity, resulting in significant inhibition zone. Test filter paper method, Oxford cup, punch method of three methods of hop polyphenols antibacterial effect of bacteria, testing showed that the punch method is simple, easy to control, antimicrobial better; golden yellow Staphylococcus aureus, Bacillus subtilis and Escherichia coli concentrations in the 0.2 4mg/mL hop polyphenol solution, the minimum inhibitory concentration (MIC) were: 0.8mg / mL, 0.8mg/mL, 1.2 mg / mL.