Study On The Technology Of Extracting Polysaccharides From Dendrobium Officinale

As a perennial Chinese herbal plant,Dendrobium officinale was widely used to resist certain diseases,such as cancer,inflammation,fatigue,high blood sugar and blood lipids,enhancing immunity,etc.Studies have reported that the pharmacological effects of Dendrobium officinale were mainly derived from its active ingredients,such as polysaccharides,alkaloids,flavonoids,polyphenols and amino acids.Among them,Dendrobium officinale polysaccharide（DOP）is the most important component,which has been reported to reduce blood lipids,blood pressure and blood sugar.It could also be used to enhance immunity,antifatigue,anticancer and antioxidant.Therefore,the extraction of DOP from Dendrobium officinale possesses great development value.This research firstly conducted a comprehensive research and analysis on the various influencing factors of ultrasonic-assisted extraction（UAE）,and initially explored the influence of them on the yield;then,the Kinetics of extraction process of DOP and process optimization with the influence of its main extraction factors were studied;in order to further solve the energy consumption problem caused by UAE,pulsed ultrasonic assisted extraction（PUAE）was used to study green and economical extraction method achieving lower energy input and obtaining the same amount of DOP,and further optimizing the extraction process conditions by response surface method（RSM）;finally,the physicochemical properties of polysaccharides under the corresponding extraction conditions were studied,which provided a reliable theoretical guidance for the practical application of DOP in the future.The conclusions were as follows:（1）The comprehensive analysis of each factor through single factor and orthogonal experiments found that the influences were as follows:particle size>extraction time>ultrasound power>liquid-solid ratio（L/S）>extraction temperature>ultrasound time.（2）The UAE dynamics model of DOP was established based on Fick’s second law.Kinetic and thermodynamic parameters（such as rate constant（k）,relative raffinate rate,E_a,ΔG_m,ΔH_m,ΔS_m,half-life and D_a）were obtained.RSM and engineering mathematical computing were used to carry out condition optimization analysis respectively,and the optimal conditions were obtained at 353.15 K,60:1,60%and 150 min,and the yield was 43.7%.（3）The introduction of pulses could not only greatly reduce energy consumption,but also reduce the degree of damage to the DOP-1 structure(The Mw of DOP-1_UAE and DOP-1_PUAE are 148.2 k Da and 232.0 k Da,respectively).Using RSM to optimize the conditions,the optimal extraction conditions were obtained as L/S ratio of 65:1,temperature of 73°C,power of 74%,duty cycle of 60%,and pulse repetitions of 360 times.（4）DOP-1 could soluble in water,but insoluble in ethanol,methanol or acetone.It was a non-reducing polysaccharide possessing good thermal stability with protein content of 0.03%and uronic acid content of 23.8%.And further characterization found that DOP-1 was an irregularly aggregated acidic heteropolysaccharide consisting of sugars in the form ofβ-pyranose,mainly containing Man,Glc,Xyl and Ara in a molar ratio of 607.88:88.42:4.21:1.And DOP-1 possesed significant chelating or scavenging activities against Fe²⁺,hydroxyl radicals and DPPH.The main innovations of this research are:for Dendrobium officinale polysaccharides,the ultrasonic extraction process conditions were improved;the kinetics and thermodynamics of the extraction process were studied,and the process was optimized using engineering mathematical calculation and analysis;then the process conditions were further optimized for the energy consumption problem.