Structural characterization and cardioprotective activities of natural polysaccharides from Apocynum venetum L

Apocynum venetum L. represents a species with medicinal-food homology that is utilized in the management of hypertension and is widely consumed as a health-promoting tea in East Asia. This study reports the identification and characterization of two novel polysaccharides (PSs), AV1-N1 and AV2-N1, extracted from A. venetum L. The PSs were purified with a DEAE Seplife FF an ion exchange column and a Sephacryl S-400HR gel column and characterized by monosaccharide composition, FT-IR spectroscopy, methylation, and NMR spectroscopic analyses. It was determined that AV1-N1 and AV2-N1 were primarily composed of arabinose and galactose in varying proportions, with average molecular weights of 64.1 kDa and 58.8 kDa, respectively. The primary structure of both AV1-N1 and AV2-N1 predominantly comprises the R → 6)-β-D-Galp (1 → R) unit, featuring α-L-Araf (1 → R) branches at the C-3 position. Both AV1-N1 and AV2-N1 possess a reducing end characterized by the R → 3,6)-β-D-Galp (1 → R) unit and share identical nonreducing ends, specifically the R → 5)-α-L-Araf (1 → R) residue. In addition, this study provides the first comprehensive evaluation of the cardioprotective activities of A. venetum L. PSs, demonstrating significant protective effects against DOX-induced heart failure. Notably, at identical concentrations, AV2-N1 demonstrates more pronounced therapeutic efficacy than AV1-N1 across evaluation indicators including pericardial edema area, heart rate, ejection fraction, and cardiac output. It is postulated that AV2-N1 may enhance ampk, pgc-1α, nrf2, gpx4a, ho-1, and prdx1 gene expression, thereby effectively inhibiting reactive oxygen species (ROS) production and mitigating oxidative damage, ultimately exerting cardioprotective effects. These findings hold significant promise for the further development and utilization of A. venetum L. PSs.