Structural characterization of two novel heteropolysaccharides from Catharanthus roseus and the evaluation of their immunological activities

Catharanthus roseus, a plant with significant therapeutic value in Chinese folk medicine, contain numerous secondary metabolites. However, the primary metabolites, specifically polysaccharides which might play an important role in immunotherapy, have received limited attention. In the present study, two novel polysaccharides, designated as CRPS-1 and CRPS-2, were isolated from C. roseus. The structures of CRPS-1 and CRPS-2 were characterized using a combination of HPSEC, HPLC, IR, GC‐MS, 1D NMR and 2D NMR. Both CRPS-1 and CRPS-2 were identified as homogeneous heteropolysaccharides. Additionally, the weight-average molecular weight of CRPS-2 was lower than that of CRPS-1. The backbone of CRPS-1 was composed of 1,3-α-L-Araf, 1,5-α-L-Araf, 1,3,5-α-L-Araf, 1,3,4-α-L-Rhap, 1,3-α-D-Galp, 1,3,4-α-D-Galp, 1,4-β-D-Manp, and side chains comprised of T-α-L-Araf, T-β-D-Manp, and β-D-Glcp-(1 → 3)-α-D-Galp-(1 → 3) -α-L-Rhap-(1→. CRPS-2 mainly consisted of 1,3-α-D-Galp, 1,3,4-α-D-Galp, 1,6-β-D-Manp, 1,5-α-L-Araf, 1,3,5-α-L-Araf, 1,3-α-L-Rhap and 1,3,4-α-L-Fucp with complex branching structures. Furthermore, CRPS-2 could significantly enhance proliferation and phagocytosis, as well as the secretion of cytokines in RAW264.7 cells. It demonstrated potent immunoregulatory activity by activating the MAPK/Akt/NF-κB signaling pathways. In summary, the utilization of galactose-enriched and low-molecular-weight polysaccharides exhibits great potential in the advancement of innovative functional foods that may provide health benefits.