The Mechanism Of Ultrasound-synergized Electrostatic Field Extraction Of Polysaccharide From Hemerocallis Citrina Baroni And Structure Characterization

In the paper,the effect of ultrasound-synergized electrostatic field extraction(UEE)on the antioxidant activity of crude polysaccharide from Hemerocallis citrina baroni(HCP)was studied.The effect of UEE on the aroma components of H.citrina water extract and the structure of extraction residues were also investigated.Meanwhile,the mechanism of UEE of polysaccharides from H.citrina were studied as well.Likewise,the antioxidant activity and structure of polysaccharides from H.citrina were analyzed.The results showed that:Under the extraction parameters of liquid-to-solid ratio(25mL/g)and electrostatic field pulsed frequency(600s-1),four factors of extraction time,extraction temperature,ultrasonic power and electric field voltage all affected the antioxidant activity of HCP.The antioxidant activity of HCP was helpful improved with the increasing extraction time,the proper going-up extraction temperature,the rising ultrasonic power and appropriate increase of electric field voltage.With the extension of extraction time,the clearance rate of · OH radical and DPPH radical of HCP increased first and then decreased.Excessive extraction temperature would exacerbate the gelatinization of HCP and reduce the antioxidant activity of HCP.The higher ultrasonic power may cause the disintegration of the structure of HCP and lower the antioxidant activity.Too high electric field voltage would degrade or denature the dissolved polysaccharides,resulting in the weaker antioxidant activity of HCP.The antioxidant activity of HCP extracted from ultrasonic extraction(UE),electrostatic field extraction(EFE),and ultrasound-synergized electrostatic field extraction(UEE)were compared respectively.The results showed that the synergy between ultrasound and high voltage electrostatic field can enhance the antioxidant activity of HCP,and the pulse frequency of electric field can also affect the antioxidant activity of HCP.The variation of aroma components in H.citrina extract before andafter extraction of HCP were studied.The results indicated that UEE increased the relative content of alcohols,esters,alkanes,and phenols in the extract of H.citrina,significantly reduced the relative content of aldehydes and olefins,which related to the synergetic effect of ultrasound and high voltage electrostatic field.The activation energy provided by ultrasound-synergized electrostatic field dramatically promoted the degradation reaction and esterification reaction in solution.The molecular morphology of H.citrina solid residues obtained by UE,EFE,and UEE were observed.The results showed that UEE had the highest ragmentation degree of daylily materials,and the synergy between ultrasonic field and high voltage electrostatic field greatly enhanced the efficiency of mass transfer,allowing the dissolution of components in H.citrina tissue.The synergetic mechanism of UEE was explored and the synergetic effect was verified by measuring the conductivity,pH value and polysaccharide extraction rate.Not only that,the sonochemical yield under the synergetic effect of ultrasonic field and electric field was measured and the synergy efficiency was calculated as well.The motion of cavitation bubbles under the superposition of ultrasonic and electric field were also analyzed.The results showed that the micro-jets generated by ultrasonic cavitation bubbles,as well as the perforation and stimulation of cell membranes caused by high-voltage electrostatic field,secondary effects such as the generation of shock waves,cavitation,and free radicals,increased the the crush degree of raw materials.There existed significant synergetic effect indeed between ultrasound and high voltage electrostatic field.High voltage electrostatic field can enhance the cavitation effect of ultrasound and increase the sonochemical yield of ultrasound,thereby improving the extraction efficiency.Acoustic pressure amplitude,ultrasonic frequency,initial radius of cavitation bubbles,and electric field voltage were important factors influencing the cavitation bubble motion.Polysaccharides from H.citrina obtained under the optimum extraction condition was processed sequentially by a series of process,including deproteinization,decolorization,alcohol precipitation,vacuum concentration and freeze-drying,thereby obtaining 1.917%light brown crude polysaccharides named HCP.After HCP was separated by DEAE-52 column,water-washing elution composition HCP-W(yield of 30.80%),solution of 0.1 mol/L NaCl elution composition HCP-1(15.05%),solution of 0.3 mol/L NaCl elution composition HCP-3(14.20%)and solution of 0.5 mol/L NaCl elution composition HCP-5(2.40%)were obtained.The antioxidant activity of HCP and purified HCP-W,HCP-1,HCP-3 and HCP-5 in vitro were investigated separately.It turned out that the polysaccharides of H.citrina all had expressing varying degrees of scavenging abilities of DPPH and · OH radical.The antioxidant activity of HCP was significantly higher than that of HCP-W,HCP-1,HCP-3 and HCP-5,which related to the impurities retained in HCPS such as flavonoids and polyphenols.The results of fractional purification of HCP-W,HCP-1 and HCP-3 on the Sephadex G-100 column were as follows:Two elution peaks were obtained by HCP-W,respectively defined as HCP-Wa and HCP-Wb,and HCP-Wb is the main component;An elution peak was obtained separately by HCP-1 and HCP-3,named HCP-1a and HCP-3 a respectively.The results of UV spectra scanning results proved that HCP-Wb,HCP-la and HCP-3a contained no impurity components such as nucleic acids and proteins.The gel permeation chromatography(GPC)graph showed that HCP-Wb,HCP-1a and HCP-3 a were homogeneous polysaccharides with the weight average molecular weight(MW)of 4217,93468 and 162167,respectively.The structure analysis of polysaccharides indicated that HCP-Wb was made up primarily of L-fucose,D-galactose,D-glucose,and D-mannose with a molar ratio of 1.1931:4.4675:8.6569:4.1008 and existed monosaccharides with a pyran ring and ?-D-glucosides.HCP-1a was linked by ?-glycosidic bonds and made up primarily of L-fucose,L-arabinose,D-galactose,and D-glucose with a molar ratio of 1.3277:1.8609:9.0281:4.1137.Meanwhile,it may contain-COOH and monosaccharides with the pyran ring configuration,which was a polysaccharide molecule connected by a beta-glycosidic bond.HCP-3 a mainly contained L-rhamnose,L-arabinose,D-galactose and D-glucose with a molar ratio of 0.1203:0.5811:1.8080:1.3127 which had the structure of pyran ring.