Process Optimization of Sargassum fusiforme Polyphenols and Their Cytoprotective Effects Against Oxidative and Inflammatory Injury, with Potential Signaling Correlates

The development of marine-derived bioactive natural products has long been constrained by the dual bottlenecks of low extraction efficiency and unclear target mechanisms. In this study, single-factor experiments integrated with response surface methodology were employed to systematically establish an ultrasound-assisted high-efficiency extraction system for Sargassum fusiforme polyphenols (SP). The optimal extraction was achieved under the following conditions: ethanol concentration of 50%, liquid-to-solid ratio of 40 mL/g, ultrasonic power of 150 W, temperature of 50 °C, and extraction time of 60 min. Under these conditions, the experimentally obtained SP yield reached 38.91 ± 0.82 mg/g, showing no significant deviation from the model-predicted value (p > 0.05), thereby validating the reliability of the established process. In functional assessments, SP exhibited a mitigating effect on oxidative stress and inflammatory injury in cultured RAW 264.7 macrophages. In cellular assays, SP treatment was associated with elevated activities of endogenous antioxidant enzymes (SOD, GSH-Px and CAT), alongside reduced levels of pro-inflammatory mediators (NO, TNF-α, IL-1β, PGE2 and IL-6) and an increased level of IL-10 in LPS-stimulated macrophages. Collectively, this study establishes an efficient laboratory-scale extraction protocol for SP and presents in vitro evidence for its cytoprotective effects. These findings provide an empirical basis for future investigations into the bioactive potential of this marine polyphenol.