Research On Extraction, Purification, Structure Determination And Antioxidant Of Carbohydrates In Yacon

Smallanthus sonchifolius?or Yacon?is native to Andes of South America,and mainly distributed in sichuan,yunnan and other places.Smallanthus sonchifolius is sweet and crisp,and also rich in moisture and polysaccharides.It has numerous physiological activities,such as hypoglycemia,blood lipids and so on.In this paper,the roots of smallanthus sonchifolius was chosen as raw materials,the extraction,separation and purification as well as anti-oxidative ability were studied.The results were as follows:Microwave assisted extraction was used to extract crude polysaccharides,which was optimized by single-factor experiment and response surface method.The optimum conditions of extraction were as follow:microwave power of 486 W,microwave time of 160 s,liquid-to-solid ratio as 53:1?mL/g?.The polysaccharides yield was 89.09%under the optimal conditions mentioned above.The obtained yacon crude polysaccharides were deproteinized by Sevag method,decolorized by macroporous resin ADS-21,and purified by DEAE-52 cellulose column chromatography and sephadex gel column chromatography.The content of pure polysaccharide,measured by phenol-vitriolic colorimetry,was 96.57%.The purified yacon polysaccharide was observed to be absence of protein and nucleic acid by using ultraviolet-visible spectrum.The distribution of molecular weight was 13832 Da analyzed by gel prepacked column.The analysis of infrared spectra and nuclear magnetic resonance carbon spectra shows that the polysaccharide is a variety of heteropolysaccharide,consisting of mannose,glucose and galactose.The main linkage types of yacon polysaccharides were proved to be?1?3?-linked?-L-Man,?1?2,6?-linked?-D-Glc,?1?6?-linked?-D-Glc,?1?6?-linked?-D-Gal and?1?6?-linked?-D-Man.Scanning electron microscopy showed that the polysaccharides of cedars appeared a single rod shape or clustered distribution?smooth flake or dense reticular structure?.Further research on the ability of antioxidation showed that the yacon crude and pure polysaccharide had a relatively weak capability of Fe³⁺reducing power,but stronger scavenging activities of many free radical such as ABTS,DPPH and OH.When the concentration of crude polysaccharide reached 150 mg/L,the clearance rate of ABTS,DPPH and OH free radicals were 24.88%,49.56%and 27.34%respectively.When the concentration of pure polysaccharide reached 150 mg/L,the clearance rate of ABTS,DPPH and OH free radicals were 22.65%,37.49%and 9.48%respectively.