Study On The Controlled Extraction Of Active Substances From Perilla Stem By Hydrothermal Acid

Perilla stalks are rich in lignocellulose and high value-added natural active substances.The current disposal method is mostly directly returning to the field,resulting in the loss of natural active substances of perilla stalks.In this paper,the hydrothermal reaction is introduced into the extraction technology of natural active substances from perilla stems,combined with the advantages of acid regulation,to research on the extraction of high value-added luteolin,ferulic acid and other active substances,and reveals the mechanism of the hydrolysis of wood fiber,the leaching of active substances provides theoretical support and technical reference for the value-added development and resource utilization of perilla stalks.In order to reduce the resistance to dissolution and mass transfer of active substances,the amount of luteolin extracted as an evaluation index was used to compare the hydrothermal acid control method,hydrothermal method,ultrasonic method,enzymatic hydrolysis and other methods on the energy efficiency of perilla stalk lignocellulose hydrolysis,and analyze the hydrothermal system reaction medium ethanol,hydrothermal time,and hydrothermal temperature have an effect on·OH,and the correlation between the hydrolysis of lignocellulosic fibers and the dissolution of active substances is proved;the response surface method is used to optimize the suitable conditions for hydrothermal acid-controlled extraction of luteolin;SEM,FTIR and BET characterization and analysis of the changes in the phase structure of the perilla stem substrate before and after hydrothermal acid control,and proved the hydrothermal acid control on the hydrolysis of lignocellulosic fibers.In order to reveal the dissolution mechanism of active substances from perilla stems,a diffusion model of luteolin was established to obtain diffusion parameters such as diffusion rate constant K_tand boundary layer thickness constant C;a kinetic model was established to obtain effective diffusion coefficient D_s,extraction rate constant K_band activation Energy E_aand other kinetic parameters;using thermodynamic equations to calculateΔH_m,ΔS_mand other thermodynamic parameters.In order to obtain high-purity active substance monomers of perilla stalks,semi-preparative high performance liquid chromatography was used to screen and obtain suitable conditions for the separation and purification of active substances such as luteolin,and evaluate the economic benefits of the extraction of active substances from perilla stalks..conclusion as below:（1）Comparison of luteolin extraction methods shows that hydrothermal acid control method（227.24μg/g）>enzymatic method（38.64μg/g）>hydrothermal method（32.45μg/g）>ultrasonic method（30.21μg/g）),citric acid（421.19μg/g）>malic acid（240.25μg/g）>acetic acid（198.54μg/g）;the medium solvent ethanol,hydrothermal time,hydrothermal temperature influence·OH production,hydrothermal system subcritical state amount of·OH produced is 2.74～9.09μmol/L,the cellulose hydrolysate D-glucose is 0.18～0.98 mg/m L,the hemicellulose hydrolysate D-xylose is1.33～10.06 mg/m L,indicating the hydrothermal acid control can effectively realize lignocellulosic hydrolysis and simultaneous leaching of luteolin.（2）The optimal conditions for obtaining luteolin extraction by response surface methodology are hydrothermal time 120 min,hydrothermal temperature 230℃,material-to-liquid ratio 1:20 g/m L,and citric acid mass concentration 1%.Under these conditions,luteolin The extraction amount is（901.049±0.60）μg/g.The primary and secondary factors affecting the extraction of luteolin are hydrothermal temperature>hydrothermal time>citric acid mass concentration>material-to-liquid ratio,and the interaction of hydrothermal temperature and hydrothermal time effect and the square effect of the mass concentration of citric acid have a significant influence on the extraction amount of luteolin.（3）Under suitable conditions,FTIR analysis shows that hydrothermal acid control can help lignocellulose C–O–C weaken,C=C disappear,-CH₂increase,and promote the hydrolysis and rupture of glycosidic bonds in lignocellulose;SEM clearly shows purple There are holes on the surface of the perilla stem substrate.The specific surface area of the perilla stem substrate measured by BET is 2.1118 m²/g,which is 6.05 times more than before treatment,indicating that hydrothermal acid control can effectively destroy the dense structure of perilla stem and facilitate the dissolution of active substances.（4）The diffusion model shows that there are three stages in the extraction process of luteolin:rapid leaching（Ⅰ）,internal diffusion（Ⅱ）,solid-liquid diffusion（Ⅲ）,and the change of the thickness constant C of the reaction boundary layer is C_Ⅰ<C_Ⅱ<C_Ⅲ,The diffusion rate constant K_tincreases first and then decreases.The kinetic model calculated that the extraction rate constant K_bof luteolin is 0.0188～0.0404 min^-1,the apparent activation energy Ea is 17.90 k J·mol^-1,and the effective diffusion coefficient Ds is 0.13×10^-4～0.28×10^-4mm²·min^-1,the minimum raffinate rate y is 1.75%.The thermodynamic equation is calculated,?H_mis 34.54～110.06 k J·mol^-1,?S_mis41.07～238.20 J·mol^-1·K^-1,?H_m>0,?S_m>0,indicating that the hydrothermal acid controlled extraction of Osmanthus Herbalin is a process of endothermic entropy increase.（5）Use preparative chromatography to separate and purify five active substances.The appropriate conditions for separation and purification are V methanol:V water=50～32%:50～68%,flow rate 15 m L·min^-1,injection volume 10 m L,vanilla The resolution of aldehyde,ferulic acid,luteolin,oleanolic acid,and luteolin are 1.79,1.55,3.02,2.56,and 2.74,respectively,which are considered to be completely separated;the preparation rate of vanillin by freeze drying is 41.34%,purity Is 98.94%,ferulic acid production rate is 24.09%,purity is 94.67%,luteolin production rate is 18.58%,purity is92.40%,oleanolic acid production rate is 27.53%,purity is 85.45%,luteolin The preparation rate is 31.69%and the purity is 97.18%.It provides high-purity monomers for the development of multi-product products of perilla stems,and realizes the value-added development and resource utilization of perilla stems.