Influence Of Dynamic High-pressure Microfluidization On Extraction,Structure And Antioxidant Activities Of Polysaccharides From Lotus Leaf

Lotus(Nelumbo nucifera Gaertn) has been cultivated widely in China since ancient times. Lotus leaf contains a variety of biologically active substances and has great value in variety of areas. Lotus leaf polysaccharide(LLP) is an important functional component in the lotus leaf. At present, many researches studied on LLP were about its function, structure, etc and Japanese researches were the leading position. In China, systematic studying on LLP began very late and the technology is backward. So researches about LLP are very limit.In this case, the objectives of this study were to explore the potential of lotus leaves in producing polysaccharides and to optimize the extraction conditions. In this work, Dynamic high pressure microfluidization (DHPM) homogenizer was used to extract polysaccharides from lotus leaves with response surface methodology and compared with polysaccharides which extracted with hot water. The structural characteristics and the antioxidant activities of the polysaccharides were determined. The main contents and conclusions of the study are as follows:1. According to the results of single factor experiments, response surface methodology was employed to optimize the DHPM-assisted extraction. The optimal DHPM-assisted extraction conditions of LLP were determined as follows:processing pressure180MPa, extraction temperature76℃and extraction time50min, the yield of LLP under these conditions was6.31%. The optimal hot water extraction conditions of LLP were ratio of liquid to solid35:1, extraction time86min and extraction temperature76℃, the yield of LLP under these conditions was2.95%.Make a comparison among DHPM-assisted extraction and hot water extraction, we found that extraction temperatures of the two methods were similar. When the extraction temperature was about75℃, both of the two methods got the best yield of LLP. The extraction time of DHPM-assisted extraction and hot water extraction were slightly different, they were50min and86min, respectively. So the DHPM-assisted extraction is a relatively effective method for LLP extraction.2. Study the purification process of D-LLP and H-LLP. Sevage reagent was used to remove the protein and two kinds of enzyme to degrade the starch. DEAE-52cellulose ion exchange column chromatography also used to purify the two polysaccharides, the results showed that both D-LLP and H-LLP had single, symmetrical elution peaks with0.1mol/L NaCl and0.2mol/LNaCl as the eluent and each of the components was acidic polysaccharide.3. Purity identification results showed that D-LLP-1and H-LLP-1were high purity polysaccharides. UV spectrum and color reaction indicated that D-LLP-1and H-LLP-1were non-starch, non-reducing sugar polysaccharides which combined without protein and polyphenol.4. Monosaccharide composition analysis revealed that both D-LLP-1and H-LLP-1contained rhamnose, fucose, arabinose, xylose, galactose, mannose and glucose, but the relative molar percentages of each monosaccharide were significantly different. The molecular weights of D-LLP-1and H-LLP-1were549540Da and578096Da, respective.5. The antioxidant activity experiment showed that the D-LLP-1had better abilities on scavenging DPPH free radicals, OH free radicals and resistance of lipid peroxidation function. Superoxide free radicals scavenging ability and reduction activity of H-LLP-1and D-LLP-1were similar, D-LLP-1was slightly better than H-LLP-1at higher experimental concentrations.