A Sulfated Polysaccharide from Red Seaweed Gracilaria caudata Exhibits Antioxidant and Antiadipogenic Activities In Vitro

This study investigated the antioxidant and antiadipogenic activities of sulfated polysaccharide (SPs) from the red seaweed <i>Gracilaria caudata</i>. First, sulfated polysaccharide-rich extracts (SPREs) from fifteen tropical seaweeds were screened to evaluate both their chemical composition and antioxidant potential. Among all samples, <i>G. caudata</i> exhibited the highest total antioxidant capacity, which justified its selection for detailed characterization. Sequential acetone precipitation produced three SPs (F1.5, F2.0, and F3.0), differing in sulfate content, monosaccharide composition, and molecular weight. In vitro assays revealed that F1.5 had the highest total antioxidant capacity and strong iron-chelating activity, while F2.0 exhibited the most effective hydroxyl radical scavenger. Importantly, F1.5 was the only SP that was non-cytotoxic to non-tumor cell lines. In 3T3-L1 preadipocytes, F1.5 attenuated H₂O₂-induced oxidative stress by reducing ROS and MDA levels and restoring GSH and SOD activity, achieving effects comparable to those of quercetin. Moreover, F1.5 inhibited adipogenic differentiation in a dose-dependent manner, as evidenced by decreased Oil Red O staining and reduced glycerol release. Collectively, these findings indicate that F1.5 exerts both antioxidant and antiadipogenic activities, highlighting <i>G. caudata</i> as a promising natural source of bioactive polysaccharides with potential nutraceutical applications. Nonetheless, further studies are required to elucidate the molecular mechanisms underlying these effects, validate the efficacy in vivo, and assess bioavailability and safety before clinical translation can be considered.