Structural characterization of a polysaccharide from Thesium chinense Turcz and its immunomodulatory activities

TCP-A, a novel homogeneous polysaccharide with a molecular weight of 84.789 kDa, was obtained by isolation and purification from TCT using a DEAE seplife FF column and a Sephacryl S-400 high-resolution column. The core objectives of this study are divided into three levels: the primary objective is to elucidate the structural characterization of TCP-A; the secondary objective is to evaluate its immunomodulatory activity both in vitro and in vivo; and the extended objective is to explore potential targets and pathways underlying the immunomodulatory effects of TCP-A. Its structure was elucidated through monosaccharide composition analysis, methylation analysis, and NMR spectra. TCP-A is mainly composed of →3)-β-D-Galp-(1→, →6)-β-D-Galp-(1→, and →3,6)-β-D-Galp-(1 → interconnected to form the main chain, with branches primarily composed of T-α-L-Araf-(1→, T-α-L-Araf-(1 → 5)-α-L-Araf-(1→, and T-α-L-Araf-(1 → 5)-α-L-Araf-(1 → 3)-α-L-Araf-(1→, featuring side chains linked at O-3. In this study, the immunoregulatory activity of TCP-A was investigated both in vitro and in vivo through cell and zebrafish experiments. In vitro experiments demonstrated that TCP-A significantly enhanced the proliferation of RAW264.7 cells and promoted the release of nitric oxide (NO), tumor necrosis factor-alpha (TNF-α), and interleukin-1 beta (IL-1β). In vivo experiments conducted on immunosuppression zebrafish revealed that TCP-A significantly increased the density of immune cells and the number of macrophages in immunosuppression zebrafish. Collectively, these results suggest that TCP-A exhibits promising immunomodulatory activity.