Pyropia haitanensis polysaccharides have attracted growing attention for their diverse biological activities. In this study, we developed a synergistic extraction approach combining ultrasonic-assisted treatment and enzymatic hydrolysis using cellulase and pectinase. Response surface methodology (RSM) was applied to optimize the extraction conditions, which were determined as follows: 1.48% cellulase, 1.47% pectinase, 180 W ultrasonic power, and 65.9 °C temperature. Under these conditions, the polysaccharide yield reached 10.184 ± 0.27%. The crude extract was then purified through sequential DEAE Sepharose FastFlow and Sephadex G-75 chromatography, resulting in the purified fraction PPHP3. Monosaccharide analysis revealed that galactose, glucose, and glucuronic acid constituted the primary components in a molar ratio of 98.3:0.46:1.24. This polysaccharide exhibited a weight-average molecular weight of 25.208 kDa, a sulfate content of 8.64 ± 0.05%. In hypolipidemic assays using oleic acid-induced HepG2 cells, PPHP3 significantly reduced intracellular triglycerides (TG), total cholesterol (TC), and low-density lipoprotein cholesterol (LDL-C), while simultaneously increasing HDL-C levels. These findings highlight the potential of P. haitanensis polysaccharides for hypolipidemic applications and establish a scientific foundation for their development in therapeutic and practical contexts.

Dysregulation of the microbiota–gut–brain axis has been implicated in Parkinson’s disease (PD), and modulation of the intestinal microbiota may offer a complementary nutritional approach. This study evaluated the preventive attenuation of MPTP-induced PD-like abnormalities by Lactiplantibacillus plantarum SHOU LAC-1 and examined associated microbiota–gut–brain axis-related changes. Forty male C57BL/6J mice were allocated to Control, MPTP, L-DOPA, and SHOU LAC-1 groups (n = 10 per group). SHOU LAC-1 was orally administered at 1 × 10⁹ CFU per mouse per day for 42 days, with MPTP administered during the final 14 days; L-DOPA was administered during the MPTP-treatment period as a positive control. Motor performance and defecatory parameters, nigrostriatal TH and α-SYN immunoreactivity, neurotrophic-support-related gene expression, inflammatory markers, glial-cell-related gene expression, Nrf2-related antioxidant gene expression, colonic histopathology and tight-junction-related gene expression, gut microbiota composition, and serum metabolic profiles were assessed. Compared with MPTP-treated mice, SHOU LAC-1-treated mice showed better motor and defecatory performance, partial preservation of nigrostriatal TH immunoreactivity, reduced α-SYN immunoreactivity, increased neurotrophic-support-related gene expression, lower central and colonic inflammatory markers and glial-cell-related gene expression, increased Nrf2/HO-1/NQO1-related antioxidant gene expression, and comparatively better-preserved colonic morphology with higher tight-junction-related gene expression. 16S rRNA sequencing and untargeted serum metabolomics further showed that SHOU LAC-1 administration was accompanied by changes in gut microbial diversity and composition and serum metabolic profiles. Overall, under this preventive experimental design, SHOU LAC-1 administration was associated with attenuation of multiple MPTP-induced PD-like abnormalities, accompanied by changes in gut microbial and serum metabolic profiles. These preclinical findings are predominantly associative; causal relationships among microbial, metabolic, intestinal, and neurological changes remain to be established, and the translational relevance of SHOU LAC-1 requires further validation.

Porphyra suborbiculata exhibits strong heat tolerance and has considerable commercial potential under rising sea temperatures; however, its bioactive components remain insufficiently explored. In this study, a heat-tolerant new strain of P. suborbiculata (PS-M4), cultivated by the College of Fisheries, was used as the experimental material. Polysaccharides were extracted using an ultrasound-assisted composite enzymatic method, and extraction conditions were optimized through single-factor experiments and response surface methodology, yielding a maximum extraction yield of 12.45 ± 0.09%. Crude polysaccharides were further purified using a purification apparatus, yielding two fractions, designated PSP-I and PSP-II. Preliminary structural characterization showed that PSP-I possessed a weight-average molecular weight (Mw) of 26.149 kDa, a number-average molecular weight (Mn) of 11.267 kDa, and a polydispersity index of 2.321. Monosaccharide composition analysis indicated that PSP-I was predominantly composed of galactose. Fourier transform infrared spectroscopy (FT-IR) revealed typical polysaccharide functional groups, and scanning electron microscopy (SEM) analysis revealed a porous lamellar morphology. In vitro cell-based assays demonstrated that PSP-I significantly alleviated ultraviolet B (UVB)-induced damage in HaCaT cells by reducing intracellular reactive oxygen species (ROS) levels, enhancing antioxidant enzyme activities, inhibiting apoptosis, and downregulating the expression of matrix metalloproteinases (MMPs). These results suggest that PSP-I has potential as a functional ingredient for mitigating UVB-induced skin damage.