Preparation,Structure Analysis And ACE Inhibitory Activity Of Konjac Oligosaccharide

Konjac is rich in glucomannan,which has many beneficial biomedical and health effects.Konjac glucomannan viscosity is large,which limits it use.The research shows that the konjac oligosaccharide can be prepared by means of the degradation of konjac polysaccharide.The medicinal value of konjac oligosaccharide is very high.Therefore,it is of significance to prepare oligosaccharide from konjac.The main research contents and results are as follows:First,the composition of konjac was analyzed.The content of protein was 7.21 ±0.12%.The total soluble sugar content was 39.28±0.27%.The reducing sugar content was 5.08±0.45%.The fat content was 0.17±0.45%.The total sugar content was 64.17±0.16%.The crude fiber content was 2.38±0.67%.The starch content was 10.23±0.22%.The pectin content was 13.09±0.54%.The soluble protein content was 1.96±0.13%.The water content was 6.06±0.13%.In this paper,the influence of solid-liquid ratio,extraction temperature,extraction time and extraction frequency was optimized by single factor and orthogonal experiment,The optimum extraction conditions were:95 ?,2.5 h,3 times and 1:100.The highest konjac polysaccharide yield was 43.01±0.12%.With the the yield of oligosaccharide and polysaccharide hydrolysis rate as indexes,the konjac polysaccharide were degraded by ?-mannitase,the optimal protease was used to optimize the enzymatic hydrolysis process by single factor and orthogonal experiment.The optimal condition is:temperature 50 ?,enzyme concentration 60 U/g(konjac),substrate concentration 1 mg/mL,degradation time 5 h.The average degree of polymerization is 4 and the highest konjac polysaccharide yield was 55.19±0.32%.The enzymolysis products of optimal enzymatic hydrolysis were detected by the methods of TLC and HPLC.It was found that the enzymolysis products obtained a small amount of monosaccharide and 5 main konjac oligosaccharide.The oligosaccharide are named P1?P5 with the highest P3 content.The results showed that the ACE inhibition rate of the product of optimal enzymatic hydrolysis was 37.50±3.64%.P5 was removed by 90%ethanol.The total acetylation of the konjac oligosaccharide was made using pyridine and acetic anhydride.The whole acetylation product was isolated and purified by silica gel column to get the acetylation P3,named AC-P3.The molecular weight of AC-P3 was 1254 Da by MALDI-TOF-MS.The specific rotation of oligosaccharide was-20°.The ethanoyl of AC-P3 was removed by sodium methoxide and the salt was removed by Sephadex G-15 to get P3.The molecular weight of P3 was 666 Da by MALDI-TOF-MS.The specific rotation of oligosaccharide was +45°.The results showed that P3 were tetrasccharide.P3 was composed of 1mol ?-glucose and 2 mol?-mannose which connected by(1?4)glucosidic bond,and the ?-mannose in the middle is linked to 1 mol of ?-galactose by(1?3)glucosidic bond.The ACE inhibition rate of P3 was determined.The results showed that the ACE inhibition rate of the P3 was 60.10±0.25%.Linear regression was carried out on the different concentrations of P3 and their corresponding ACE inhibition rate.The IC50 value of P3 was 0.791 mM.