Studies On Physicochemical Properties And Biological Activities Of Fenugreek Polysaccharide

Fenugreek（Trigonella foenum-graeeum L.）is an edible and medicinal resource,and its seeds are rich in polysaccharides,accounting for about 70%of the total amount.In this paper,fenugreek seeds were used as raw materials to optimize the extraction process,study on rheological properties,separation and purification,structure identification and biological activity of fenugreek polysaccharide.The main research contents and results were as follows:Fenugreek polysaccharide was extracted by hot water extraction,ultrasound-assisted method and ultra-high pressure assisted method.The extraction process of fenugreek polysaccharide was optimized by single factor experiment and response surface methodology.The optimal extraction conditions were as follows:pressure 314.04 MPa,liquid-solid ratio 20.04:1（g/m L）,extraction time10.76 min.Under these conditions,the yield of fenugreek polysaccharide was19.35±0.13%.In addition,the polysaccharide yield of hot water extraction method was 13.93±0.31%,and that of ultrasound-assisted method was 16.11±0.66%.The relationship between the rheological properties of polysaccharides prepared by the three methods and the concentration,storage temperature,p H and salt ions was studied.The results showed that fenugreek polysaccharide extracted by hot water（HWE-FP）,ultrasonic extraction（UAE-FP）and ultra-high pressure extraction（UHPE-FP）exhibited typical shear thinning behavior and pseudoplastic fluid characteristics.Meanwhile,at the same concentration,the apparent viscosity of the three polysaccharides were:UAE-FP>UHPE-FP>E-FP;HWE-FP,UAE-FP and UHPE-FP showed good stability to temperature,p H and salt ions.The results of dynamic rheological experiments show that HWE-FP,UAE-FP and UHPE-FP at concentrations of 0.5%and 2.5%have both high viscosity fluid properties and solid elastic properties.HWE-FP1,UEA-FP1 and UHPE-FP1 were separated and purified by DEAE-52 cellulose chromatography column,and the results showed that the HWE-FP1,UEA-FP1 and UHPE-FP1 were all neutral polysaccharides.FTIR analysis showed that fenugregonellulose polysaccharide contained mannose pyranose and galactopyranose.XRD spectra showed that there were many similar crystal morphology and lattice types in fenugreek polysaccharide.SEM analysis showed that fenugreek polysaccharide had sheet and spherical structure.At high magnification,fenugreek polysaccharide prepared by different methods had obvious structural differences.HWE-FP1,UAE-FP1 and UHPE-FP1 were rich in galactose and mannitose,but their molar ratios were different,and HWE-FP1contained rhomose with a molar ratio of 0.7%.The antioxidant activities of HWE-FP,UAE-FP and UHPE-FP were studied in vitro.The results showed that the three polysaccharides all had certain antioxidant activity in vitro,and the reducing power,metal ion chelating ability,superoxide radical scavenging ability,hydroxyl radical scavenging ability and DPPH radical scavenging ability were all HWE-FP>UHPE-FP>UAE-FP from large to small.The results showed that the inhibition zone size of HWE-FP and UHPE-FP at 5 mg·ml^-1was 9 mm and 7.8 mm,respectively.