Response surface optimization of extraction and structure and activity analysis of polysaccharides from Polygonatum kingianum Coll. et Hemsl.

【Objective】The extraction of polysaccharides from Polygonatum kingianum Coll. et Hemsl.（PKP）by dynamic high-pressure microfluidization（DHPM）were optimized and its structure and activity were analyzed，which provide technical support for the diversified utilization of PKP.【Method】Response surface methodology（RSM）was designed on the basis of single factor experiment to determine the optimal extraction conditions of PKP to determine the optimal extraction conditions by DHPM，with PKP yield as the indicators. The activities（tyrosinase inhibitory activity，α-glycosidase inhibitory activity，DPPH radical scavenging activity）and structural characteristics（infra-red spectrum，relative molecular weight，monosaccharide composition）of PKP were studied.【Result】The quadratic regression equation established by RSM and the model had good fitting degree，as follow：Y=19.55 + 0.7A + 0.78B + 0.89C + 0.28AB + 1.26AC + 0.84BC-1.84A²-4.72B²-2.3C2（R²=0.9860）（Y was extraction yield，A was microfluidization pressure，B was materialliquid ratio and C was extraction time）. Influence of extraction time，material-liquid ratio and interaction of microfluidization pressure and extraction time to PKP yield were extremely significant（P<0.01）. Influence of microfluidization pressure and interaction of material-liquid ratio and extraction time to polysaccharides yield were and significant（P<0.05）. Parameters influencing PKP yield were in the order as follows：extraction time>material-liquid ratio>microfluidization pressure. The optimal parameters were microfluidization pressure of 146 MPa，material-liquid ratio of 1∶41，extracting time of 70 min at 100 ℃. Then the polysaccharides yield was 19.57%，and 98.69% of the theoretical prediction was obtained. PKP was an acidic polysaccharide composed of 11 monosaccharides with a relative molecular weight of 35.95 kD. PKP showed strong DPPH radical scavenging ability，α-glycosidase inhibitory activity and tyrosinase inhibitory activity. The semi-suppressed mass concentration（IC₅₀）were 0.43，4.07 and 2.87 mg/mL respectively.【Conclusion】RSM is suitable for optimize the extraction parameters of PKP by DHPM. The yield of PKP obtained by this method is high and has good predictive performance. PKP has good functional activities and wide development prospect.