Structural characteristics of polysaccharides FHVP-2 isolated from Ficus hirta Vahl and its ability to effectively protect RAW264.7 cells from H₂O₂-induced and immunomodulatory activity

A novel acidic polysaccharide, Ficus hirta Vahl polysaccharide (FHVP-2), with a molecular weight of 7.823 × 10⁴ Da, was isolated from Ficus hirta Vahl. FHVP-2 primarily composed of galacturonic acid, galactose, arabinose, and rhamnose. The main-chain skeleton of FHVP-2 contains the following sequence: →3)-β-D-Galp-(1→, 4)- α-D-GalpA- (1→, 4)- α-D-GalpA-6-OMe-(1→, (1→,2,4)-α-L-Rhap-(1→,4)-α-L-Arap- (1→, 4)-α-D-Galp- (1→, α-L-Araf- (1→. In vitro studies have shown that FHVP-2 can protect RAW264.7 cells against oxidative stress induced by H₂O₂. This defense is achieved through a multifaceted response in which the release of malondialdehyde (MDA), intracellular reactive oxygen species (ROS), and lactate dehydrogenase (LDH) is reduced, while phagocytosis and superoxide dismutase (SOD) levels are increased. This response also prevents aberrant apoptosis. Further experiments indicated that the anti-apoptotic effect of FHVP-2 is closely related to the alleviation of S-phase cell cycle arrest. Moreover, FHVP-2 induces RAW264.7 cells the produce nitric oxide (NO), acid phosphatase (ACP), and lysozyme (LZM), and the secretion of IL-6, IL-1β, and TNF-α. In summary, our results suggest that FHVP-2 may serve as a new immunomodulatory agent with the potential to be used as a natural antioxidant in functional foods.