A Study On The Effect On An Ultrasound-enhanced Aqueous Two-phase Extraction And Purification Of Plant Polysaccharides

Plant polysaccharides are natural,powerful,non-cytotoxic compounds that are increasingly being used as an alternative to conventional medicine to reduce the effects of free radical-induced oxidative stress.However,enhancing their yield and bioactivity during extraction remains a challenge,since most extraction methods have the potential to degrade polysaccharides,thus affecting their bioactivity.Therefore,a one-step multi-frequency ultrasound-assisted alcohol/salt aqueous two-phase extraction technique was developed and explored in the extraction and purification of Astragalus membranaceus and Lentinus edodes polysaccharides with the main objective of improving yields and enhancing the antioxidant capacity of the polysaccharides.The set objective was achieved by:?i?selecting an appropriate aqueous two-phase system?ATPS?which was used as an extracting and purification system.?ii?Optimizing extraction parameters through Response surface methodology to improve the performance of the two-phase extraction in multi-frequency ultrasound.?iii?Applying a time-variant ultrasound?10 min,20 min,and 30min?in the desalination of the polysaccharide salt-rich bottom phase to desalt and enhance the purification of polysaccharides.Finally,the desalinated extracts were evaluated for their physicochemical,microstructure,and in vitro antioxidant capacity.The main outcomes and contents are shown as follows:1.A study on the effects of dual-frequency ultrasound-assisted alcohol/salt aqueous two-phase extraction of Astragalus polysaccharides.The study investigated the effect of dual-frequency ultrasound-assisted alcohol/salt aqueous two-phase extraction and desalination on the yield,microstructure,and antioxidant properties of Astragalus polysaccharides?APS?.Extracts were desalinated for 10(APS₁₀),20(APS₂₀),and 30(APS₃₀)minutes.A 28.40%experimental yield,well correlated to the response surface methodology predicted model was achieved.Thermodynamic parameters were non-spontaneous,irreversible,and endothermic.Moreover,ultrasound enhanced the desalination rate and did not alter the chemical structure in the APS.Fourier Transform Infrared Spectroscopy showed a similar spectrum in all the APS samples.High-performance gel chromatography and scanning electron microscopy respectively presented reduced molecular weights and altered microstructures in the samples.Monosaccharide analysis revealed the existence of xylose,mannose,galactose,glucose,arabinose,rhamnose,and ribose in the APS samples.Moreover,the APS₂₀ showed strong hydroxyl and 2,2-diphenyl-1-picrylhydrazyl radical scavenging activities,thus showing its potency in reducing oxidative stress.Hence,this study demonstrated that coupled ultrasound and alcohol/salt ATPS is a sustainable technique,which generates high yields of simultaneously extracted products.2.A study on the effects of subcritical water extraction and ultrasound-assisted aqueous two-phase extraction and purification of Lentinus edodes polysaccharides.The effect of a synergized two-step subcritical water extraction?SWE?and simultaneous multi-frequency ultrasound-assisted alcohol/salt aqueous two-phase extraction?MFu-AATPE? on the yield,physicochemical,structural characteristics,and antioxidant activities of Lentinus edodes polysaccharides?LEPs?was investigated.Crude LEP extracted under subcritical extraction?31.14%?was purified using dual and triple frequency ultrasound-assisted aqueous two-phase systems giving a yield of 94%and 97%respectively.Compared with the dual-frequency sonication?20/40 kHz?,the triple frequency sonication?20/40/60 kHz?gave maximum yield and improved the desalination rate by 33.6%.Congo red analysis revealed triple helix structures.Gas Chromatography analysis showed the existence of mannose,glucose,arabinose,xylose,and galactose whilst spectral similarities were observed through Fourier Transform Infrared Spectroscopy.The average molecular weight?Mw?was 83.6170 Da,2384 Da,and 2387 Da for control,dual,and triple frequency samples respectively.Ultrasound treated polysaccharides displayed stronger antioxidant activities against the 2,2-diphenyl;-1 picrylhydrazyl?DPPH?,2,2?-azino-bis 3-ethylbenzothiazoline-6 sulfonic acid?ABTS?and hydroxyl radicals,thus demonstrating their potency in reducing oxidation.However,the microstructure of the triple frequency treated sample was altered compared to the dual-frequency sample.Therefore,this study demonstrated the efficacy of SWE in crude LEPs extraction and illustrated MFu-AATPE as an efficient technique that selectively isolates polysaccharides and enhances extraction efficiencies.