Changes in the physicochemical characteristics and biological activities of polysaccharides from Panax ginseng during defense against red-skin disease

Red-skin roots are a common disease symptom in cultivation of Panax ginseng, which strongly affects its quality and production. Differences in polysaccharides between red-skin and healthy ginseng were examined for the first time to elucidate their function as resistance to disease and explore their potential as active ingredients. Fluorol Yellow 088 and ruthenium red staining revealed changes in the distribution and composition of ginseng polysaccharides during defense against red-skin disease. Acid pectin content was observed to increase significantly in cell walls of the diseased epidermal tissue. Furthermore, targeted extraction approaches were used to obtain water-solution polysaccharides (WPS) and pectic polysaccharides (PP) which marked different characteristics with the health group. WPS from red-skin roots exhibited novel pectic characteristics, consisting of 32.25% GalA which is 10 times more than the healthy sample, accompanied by a sharp decrease in starch content (approximately 50%). Another study on the adsorption and gel properties of PP indicated that it played an important role in disease resistance by reducing metal toxicity and increasing the strength of the cell wall. For further analysis of the abnormal pectic composition, DEAE-52 purification was used and various pectic fractions (WPS-1,2,3) consisting of the RG-Ⅰ pectic domain were obtained. The analysis of antioxidant and immunoactivity was performed to explore the effect of characteristic changes on biological activities. Higher radical scavenging ratios of DPPH and ABTS indicated that red-skin fractions had stronger antioxidant activities. Stronger promotion effect on Raw264.7 secretion of TNF-α and IL-1α represented the higher immunological activities. Therefore, the red-skin ginseng polysaccharides could be utilized in the pharmaceutical industry to compensate for the value loss caused by red-skin roots.