Characteristics and Biological Activities of a Novel Polysaccharide R1 Isolated from Rubus chingii Hu

Raspberry (Rubus chingii Hu) is a Chinese herb that is rich in nutrients and has anti-inflammatory, antibacterial, antioxidant, anti-allergic, hypoglycemic, and other effects. A water-soluble polysaccharide was extracted from raspberry by using hot water extraction then purified by DEAE-Sepharose Fast Flow column chromatography. The structural characteristics of the polysaccharide (R1) are as follows: the molar ratio of the monosaccharide composition is Ara:Gal:Xyl:Glc:Man = 31.15:27.64:13.61:13.48:10.60; the molecular weight is 32,580 Da; the methylation results show that 5-Araf is the main chain and there is a presence of 3,6-Galp, 4-Xylp, and 2,3,5-Araf branches, and that terminal Araf (T-Araf) is the major telomeric sugar. It contains α and β glycosidic bonds and is highly branched, with the presence of a helical structure. In the in vitro antioxidant assay, R1 showed the highest scavenging of superoxide anion radicals at 70.38%, followed by the scavenging of DPPH radicals at 52.9% and the scavenging of hydroxyl radicals at 29.28%. In immunomodulation and anti-cancer experiments, R1 did not significantly inhibit or promote RAW264.7 cells but was able to increase the expression of anti-inflammatory cytokines in a concentration-dependent manner. It also significantly inhibited cancer cell survival. R1 enhances immunity by limiting the proliferation of cancer cells primarily through direct inhibition while promoting the secretion of pro-inflammatory cytokines. These findings reveal the potential benefits of raspberry polysaccharides and provide evidence for developing immunologically functional products from raspberry polysaccharides.