Studies On Extraction Purification And Bioactivity Of Chlorogenic Acid From Green Coffee Beans

Green coffee beans are the seeds of coffee trees.CGA is one of the main active substances in green coffee beans.CGA has important biological activities such as antioxidant and bacteriostatic activities,so it is used widely and is in great demand.In this dissertation,A-grade Katim green coffee beans were used as the research materials.Surfactant combined with an ultrasound-assisted method and response surface methodology were employed to extract CGA from the green coffee beans.The content of CGA was characterized by ultraviolet spectrophotometry.The yield of CGA was used as the evaluation index.The technology of liquid-solid ratio,extraction time and extraction temperature were optimized by the single factor and Box-Behnken design(BBD)experiments with three factors and three levels.The CGA from the green coffee beans was purified by macroporous adsorption resin.Then,its antioxidant and bacteriostatic properties and stability were studied.At the same time,the application of bacteriostasis was preliminarily studied.The main results are as follows:(1)A surfactant was selected as the extraction solvent from five solvents,which was 40% PEG400.The optimal extracting conditions are: liquid-solid ratio was 28?1(mL?g),extracting temperature was 60°C,extracting time was 50 min,CGA yield was 13.66 mg/g.(2)Six different macroporous adsorbent resins were selected to carry out static adsorption and desorbed experiments on crude extract.Comparing the static adsorption and resolution rates under different pH values,the experiment showed that NKA-9 resin was selected to purify crude extract with pH 2.The optimum purification conditions were as followed: under the conditions of 100 r/min and 25°C in the shaking bath,1 g resin and 20 mL crude extract,which was diluted 8 times and at pH 2,were used to do the static adsorption experiment,it took 5 hours to reach the static adsorption equilibrium time.The static desorbed experiment was carried out with 55% ethanol,and its equilibrium time was 7 hours.The flow rate of crude extract and desorbed solution was 2 mL/min in the dynamic adsorption and desorbed experiments.Finally,under these conditions,the purity of CGA from the green coffee beans increased from 12.90% to 46.29%,and the multiple of purification was 3.59 times.(3)The FRAP and the DPPH free radical scavenging methods were used to research the antioxidant activity of CGA from the green coffee beans in vitro.The results showed that it had antioxidant capacity and DPPH free radical scavenging capacity.Temperature had little effect on stability of the DPPH free radical scavenging capacity.Light had some effect on stability.The pH value had a significant effect on stability,which was more stable in acidic conditions than in alkaline conditions.(4)The bacteriostatic activity of CGA from the green coffee beans was evaluated by Oxford cup method and pre-added bacterial liquid pouring plate method.The results showed that it had certain inhibitory effects on Escherichia coli,Staphylococcus aureus,Bacillus subtilis and Bacillus cereus.The pH value had a significant influence on antibacterial stability of the four kinds of bacteria.The concentration of NaCl and the UV irradiation time had a certain effect on stability,but UV irradiation time had no significant effect on Bacillus subtilis.Temperature had the same regularity change on the four kinds of bacteria,but had no significant effect overall.The bacteriostatic activity of CGA from the green coffee beans was applied to red bean and orange drinks.The results showed that it could extend the shelf-life of red bean juice for about 5 days and the storage period of orange juice for about 3 days,and it could also enhance aroma and protect color of orange juice.There is abundant CGA in the green coffee beans.CGA has good antioxidant and bacteriostatic activities.This study has certain value for further research and application of CGA in the green coffee beans.