Optimization of Deep Eutectic Solvent Extraction Process of Polysaccharides from Dendrobium officinale

In order to increase the comprehensive utilization of Dendrobium officinale, a green and efficient method for extracting of Dendrobium officinale polysaccharides (DOPs) was established. This research used the extraction rate of DOPs as the indicator for the effects of three factors. These included the concentration of deep eutectic solvent (DES), extraction temperature, and liquid-to-material ratio on the efficacy of polysaccharides from Dendrobium officinale, using single-factor tests. Response surface methodology (RSM) was employed to optimize the best extraction process of DOPs and the structure of the purified polysaccharides was analyzed. The experimental results showed that the optimal process obtained after RSM was a 40% concentration of DES, an extraction temperature of 80 ℃, and a liquid-to-material ratio of 110:1 (mL/g). Under these conditions, the actual extraction rate was 33.2%±0.28%, which was close to the predicted value of 33.5%, and the purity of polysaccharide was 56.95%±1.2%. After purification by anion-exchange column and glucose gel column, the purity could reach 90.8%, and its monosaccharides were mainly composed of glucose and mannose, with a mass ratio of 43:37. It also contained a small amount of xylose, rhamnose, and ribose, and the structure contained α-glycosidic and β-glycosidic bonds. The present research provides an efficient and green extraction scheme for extracting DOP_S with DES, which has the characteristics of high polysaccharide extraction rate and greenness, providing a reference for the subsequent development of DOPs.