Optimization of Extraction and Activity of Rehmanniaglutinosa Polysaccharide by Response Surface Methodology

Taking raw rehmanniaglutinosa as the raw material, based on single-factor experiments, the extraction time, solid-liquid ratio and extraction speed were determined as the main factors affecting the yield of polysaccharides. The process parameters for extracting raw rehmanniaglutinosa polysaccharides by ultra-speed crushing were optimized by the response surface method. The optimal process parameters were confirmed as extraction time of 6 minutes, material-liquid ratio of 1∶10, and extraction speed of 4 000 r/min, the polysaccharide yield of 74.73%. The monosaccharide composition and proportion were identified by high-performance liquid chromatography assay and the ratio is 45/23/18/9/3. Furthermore, the median inhibitory concentration (IC₅₀) of rehmanniaglutinosa polysaccharide aqueous solution for DPPH was measured to be 1.32%, and for ABTS was 4.66%. This indicates that rehmanniaglutinosa polysaccharides have a good scavenging effect and antioxidant efficacy on DPPH and ABTS radicals. In the tyrosinase inhibition experiment, the half-maximal inhibition concentration was measured to be 1.12%, indicating that rehmanniaglutinosa polysaccharides have a certain whitening effect.