In this study, the effects of a homogenous porphyran from Porphyra haitanensis (PHP) on the intestinal barrier and gut microbiota were investigated. The results showed that oral administration of PHP resulted in a higher luminal moisture content and a lower pH environment for the growth of beneficial bacteria in the colon of mice. PHP significantly increased the production of total short-chain fatty acids during the fermentation process. PHP made the intestinal epithelial cells of mice arrange more tidily and tightly with a significant increase in mucosal thickness. PHP also increased the amount of mucin-producing goblet cells and the expression of mucin in the colon, which maintained the structure and function of the intestinal mucosal barrier. Moreover, PHP up-regulated the expression of tight junctions including ZO-1 and occludin, improving the intestinal physical barrier function. The results of 16S rRNA sequencing showed that PHP regulated the composition of gut microbiota in mice, increasing the richness and diversity of gut microbiota and the ratio of Firmicutes to Bacteroidetes. This study revealed that the intake of PHP is beneficial for the gastrointestinal tract and PHP could be a potential source of prebiotics in the functional food and pharmaceutical industries.

The high molecular weight and poor solubility of seaweed polysaccharides have limited their function and application. In this study, ultraviolet/hydrogen peroxide (UV/H₂O₂) treatment was used to prepare low-molecular-weight seaweed polysaccharides from Sargassum fusiforme. The effects of UV/H₂O₂ treatment on the physicochemical properties and anti-photoaging activity of S. fusiforme polysaccharides were studied. UV/H₂O₂ treatment effectively degraded polysaccharides from S. fusiforme (DSFPs), reducing their molecular weight from 271 kDa to 26 kDa after 2 h treatment. The treatment did not affect the functional groups in DSFPs but changed their molar percentage of monosaccharide composition and morphology. The effects of the treatment on the anti-photoaging function of S. fusiforme polysaccharides were investigated using human epidermal HaCaT cells in vitro. DFSPs significantly improved the cell viability and hydroxyproline secretion of UVB-irradiated HaCaT cells. In particular, DSFP-45 obtained from UV/H₂O₂ treatment for 45 min showed the best anti-photoaging effect. Moreover, DSFP-45 significantly increased the content and expression of collagen I and decreased those of pro-inflammatory cytokines, including interleukin-1β, interleukin-6, and tumor necrosis factor-α. Thus, UV/H₂O₂ treatment could effectively improve the anti-photoaging activity of S. fusiforme polysaccharides. These results provide some insights for developing novel and efficient anti-photoaging drugs or functional foods from seaweed polysaccharides.

Polysaccharides derived from diverse sources exhibit distinct rheological and gel properties, exerting a profound impact on their applicability in the food industry. In this study, we collected five Gracilaria chouae samples from distinct geographical regions, namely Rizhao (RZ), Lianyungang (LYG), Ningde (ND), Beihai (BH), and a wild source from Beihai (BHW). We conducted analyses on the chemical composition, viscosity, and rheological properties, as well as gel properties, to investigate the influence of chemical composition on variations in gel properties. The results revealed that the total sugar, sulfate content, and monosaccharide composition of G. chouae polysaccharides exhibit similarity; however, their anhydrogalactose content varies within a range of 15.31% to 18.98%. The molecular weight distribution of G. chouae polysaccharides ranged from 1.85 to 2.09 × 10³ kDa. The apparent viscosity of the LYG and BHW polysaccharides was relatively high, whereas that of RZ and ND was comparatively low. The gel strength displayed a similar trend. BHW and LYG exhibited solid-like behavior, while ND, RZ, and BH demonstrated liquid-like characteristics at low frequencies. The redundancy analysis (RDA) analysis revealed a positive correlation between the texture profile analysis (TPA) characteristics and anhydrogalactose. The study could provide recommendations for the diverse applications of G. chouae polysaccharides derived from different geographical regions.

Ultrasound-assisted deep eutectic solvent (DES) extraction has emerged as a promising green and intensified strategy for recovering natural polysaccharides from plant, algal, fungal, and other biological matrices. By coupling acoustic cavitation with tunable solvent microenvironments, this approach can enhance cell-wall disruption, solvent penetration, mass transfer, and polysaccharide solubilization while reducing reliance on harsh acidic, alkaline, or organic solvents. However, extraction efficiency alone is insufficient to define process quality because ultrasound-assisted DES systems may also reshape the molecular weight distribution, monosaccharide composition, uronic acid or sulfate content, substitution pattern, charge density, conformation, surface morphology, and physicochemical behavior. These structural consequences directly influence downstream bioactivities, including antioxidant, hypoglycemic, prebiotic, anti-inflammatory, and anti-ulcerative colitis effects. This review critically summarizes the mechanistic foundations of ultrasound–DES synergy, analyzes how extraction conditions determine polysaccharide structural outcomes, and highlights the importance of linking structure with functionality. Emerging data-driven approaches, including solvent prescreening, COSMO-RS, and machine learning-assisted process optimization, are also discussed as supporting tools for navigating the multidimensional extraction space. However, their current application to the direct prediction of polysaccharide structural outcomes remains limited. Future progress will require standardized datasets, advanced structural characterization, causal structure–activity validation, and scalable process engineering. Overall, ultrasound-assisted DES extraction should be viewed as a structure-sensitive extraction platform whose performance depends on the coordinated control of solvent properties, acoustic conditions, biomass characteristics, and downstream processing.