Extraction,Purification,Stability And Antioxidant Activity Of Polyphenols From Camellia Oleifera Abel.Leaves

Camellia oleifera Abel.is a unique oil crop in China.In recent years,with the increase of the planting area of Camellia oleifera Abel.,the amount of its leaves has also increased during pruning and shaping.Polyphenols which are high in leaves have strong antioxidant activities.But Camellia oleifera Abel.leaves have always been used as waste,and cause great waste of polyphenol raw materials.If the waste resources can be used reasonably and effectively,it is of great significance to increase the added value of the leaves.Therefore,this study uses the Camellia oleifera Abel.leaves as raw material,preferably selects the drying method,researches and optimizes the extraction and purification process of polyphenols,and explores its stability and antioxidant activities.The main research contents and results were as follows:(1)Drying pretreatment of Camellia oleifera Abel.leavesCompared with the vacuum and vacuum freeze-drying,it was more efficient and time-saving to use heat pump and hot air to dry Camellia oleifera Abel.leaves.After that,the influence of drying temperature would be further discussed,and the corresponding mathematical model was established for the drying process.The results showed that the temperature rise was beneficial to shorten the drying time.When the temperature rose by10°C,the drying time was reduced by half.In addition,the drying rate also increased with the increase of temperature.The total polyphenols content of the leaves decreased with the increasing temperature.When the temperature was 70?,the drying time of heat pump and hot air needed was 3 h,but the latter had higher total polyphenols content,so selected the hot air 70?to dry the leaves.Page model could better predict the water changes in hot air drying process within the test conditions.(2)Study on extraction process of Camellia oleifera Abel.leaves polyphenolsOn the basis of single factor experiment,the response surface method was used to optimize the extraction process of Camellia oleifera Abel.leaves polyphenols.Then the prediction ability of response surface and artificial neural network model was compared,and the dynamics and thermodynamics of extraction process were also investigated.The results showed that the optimal extraction conditions were:time 35 min,temperature 69?,ethanol volume fraction 32%,solid-liquid ratio 1?69,and the polyphenol extraction amount was 67.31 mg/g under this condition.Compared with the response surface,the artificial neural network model had a larger R²,smaller RMSE and RE,so it had better prediction performance of polyphenol extraction results of the leaves.Temperature increase helped to increase the reaction rate and the polyphenol equilibrium concentration,and it could shorten the equilibrium time.The activation energy of the extraction process was9948.5 J/mol.?G<0,?H>0,?S>0,indicated that the extraction process was a spontaneous,endothermic reaction,and the degree of chaos in the solution increases.(3)Macroporous resin purified Camellia oleifera Abel.leaves polyphenolsThe suitable macroporous resin for purifying Camellia oleifera Abel.leaves polyphenols was screened,the single factor test was carried out to explore the optimal conditions for dynamic loading and elution,and the kinetics and thermodynamics of the adsorption process were also studied.The results showed that HPD-600 was selected to purify the polyphenols because it had good adsorption and desorption effects.The adsorption and elution efficiency were higher under the conditions which were the loading rate 2 m L/min,loading concentration 2 mg/m L,60%ethanol solution as elution,the elution flow rate 3 m L/min,elution volume 60 m L.After purification,the purity increased from18.49%to 40.05%.Diffusion was the rate control step of the adsorption process.With the solution concentration increased and the temperature rose up,the the adsorption rate was also increased.The activation energy of the reaction was 9877 J/mol.The resin adsorption performance conformed to the Freundlich model,and the thermodynamic parameters were?G<0,?H<0,?S<0.(4)Stability of Camellia oleifera Abel.leaves polyphenolsThe effects of temperature,light,dark,p H,oxidant(H₂O₂)and reducing agent(Na₂SO₃)on the stability of Camellia oleifera Abel.leaves polyphenols were investigated.The results showed that the concentration of polyphenols did not change much in the temperature range from 4 to 100?which meant stable.Under the condition of avoiding light,the preservation effect of polyphenols was better.When p H?10,the concentration of polyphenols in leaves remained basically unchanged.When p H was 12,the concentration of polyphenols decreased sharply and the stability deteriorated.H₂O₂ and Na₂SO₃ had great influence on the stability of polyphenols.And Na₂SO₃ was more destructive.(5)Study on antioxidant activity of Camellia oleifera Abel.leaves polyphenolsThe antioxidant activity of Camellia oleifera Abel.leaves polyphenols,VC,BHT,tea polyphenols were explored.The results showed that the leaves polyphenols had well free radical scavenging abilities,and the abilities stronger with the increase of polyphenol concentration,which were stronger than VC but weaker than tea polyphenols under the same concentration.For DPPH·and O₂^-·,the scavenging abilities of purified polyphenols were stronger than the crude extract.As for ABTS+·,the activity of two was equivalent.The polyphenol could delay the oxidation of camellia seed oil and peanut oil effectively,and the antioxidant activities of purified were better.Adding the same amount,the activities of the leaves polyphenols were weaker than BHT and tea polyphenols.Besides,the antioxidant effect of polyphenols on peanut oil was weaker than that of camellia seed oil.