The immunomodulatory effects of Bangia fusco-purpurea polysaccharides (BFP) in a mouse model of cyclophosphamide (CTX)-induced immunosuppression were investigated. As a result, BFP intervention significantly improved natural killer (NK) cell viability, macrophage phagocytosis and carbon clearance capacity, enhanced T-lymphocyte proliferation, up-regulated the proportions of CD4⁺, down-regulated the proportions of CD8⁺ T cells, increased the ratio of CD4⁺/CD8⁺ cells, reduced the proportion of Th17 cells and the ratio of CD3^-CD19⁺ B cells, and increased the levels of serum hemolysin, immunoglobulin (Ig) A, IgG and immune-related cytokines such as interleukin (IL)-2, IL-6, tumor necrosis factor-α (TNF-α), and interferon-γ (INF-γ), which demonstrated its potent regulatory effects on nonspecific immunity, cellular immunity and humoral immunity in immunosuppressed mice. Furthermore, the effects of BFP on the surface receptors of intestinal immune cells in immunosuppressed mice were analyzed. It was found that BFP significantly downregulated the mRNA (P < 0.05) and protein (P < 0.01) expression of Toll-like receptor 2 (TLR2), TLR4, IL-6 and TNF-α. Based on this, we speculated that BFP can enhance the immunity through the regulation axis of the TLR2/TLR4 downstream signaling pathway. This study provides scientific support for in-depth understanding of the nutritional value of sea foods and promoting the incorporation of sea foods into residents' diets.

In order to explore the microfloral succession in Takifugu flavidus during storage at 0 ℃, the spoilage bacteria were detected by 16S rDNA sequencing, the dominant spoilage bacteria in the late stage of storage were identified, and the changes in the microbial flora and the spoilage capacity of the dominant spoilage bacteria were analyzed. The results showed that the refrigerated shelf life of T. flavidus was about 5 days. In the early stage of storage (0–3 days), T. flavidus had the highest number of species of bacteria, including Pseudomonas, Streptophyta, and Shewanella, while in the late stage (6–15 days), the bacterial species were concentrated mainly in Pseudomonas and Shewanella. Ten dominant spoilage bacteria were isolated and identified, Shewanella and Pseudomonas accounting for a high proportion. Moreover, the spoilage capacity of several common dominant spoilage bacteria was analyzed, revealing that the decreasing order of the spoilage capacity was Pseudomonas fluorescent > P. azotoformans > Shewanella hafniensis > S. baltica. The results of this study provide a reference for understanding the spoilage mechanism of T. flavidus during cold storage and extending its shelf life.

To obtain collagen peptides with the ability to stimulate cholecystokinin (CCK) secretion, collagen was extracted from puffer fish skin and hydrolyzed with alkaline protease. The CCK secretion-promoting activity of collagen peptides with different hydrolysis degrees was evaluated using an in vitro enteroendocrine STC-1 cell model. The results showed that the peptide with a hydrolysis degree of 12% had the highest CCK secretion-promoting activity. This peptide was separated and purified using a YMC ODS C₁₈ column. Six peptide sequences were identified using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Among them, three peptides, LSGK, LPGKPGL and KMTPT, had significant CCK secretion-promoting activity. This study provides a theoretical basis for the application of puffer fish skin peptides in regulating intestinal CCK secretion and provides new ideas for the development of functional products based on puffer fish skin peptides.

A water-soluble polysaccharide, designated BFP-3, was isolated from Bangia fuscopurpurea by hot water extraction, anion-exchange, and size-exclusion chromatography and tested to determine its antitumor activity. The structural characteristics of BFP-3 were investigated by chemical and spectroscopic methods, including partial acid hydrolysis, methylation analysis, one- and two-dimensional nuclear magnetic resonance, and gas chromatography-mass spectrometry. The results showed that BFP-3 was mainly comprised of rhamnose, arabinose, mannose, glucose, and galactose. Moreover, the weight-average molecular weight of BFP-3 was estimated to be approximately 333 kDa. The backbone of BFP-3 was primarily composed of repeating 5-α-l-Araf-1→(4-α-d-Glcp-1)₄→4,6-β-d-Manp-1 units, and the side chains consisted of repeating β-d-Galp-1→(4-β-d-Galp-1)₄→4,6-β- d-Galp-1→3,4-α-l-Rhap, β-l-Arap-1→(3-β-d-Galp-1)₃, and β-l-Arap-1 units. Counting Kit-8 assays revealed that BFP-3 significantly inhibited the proliferation of A2780, COC1, SKOV3, HO-8910, and OVCAR3 ovarian cancer cells in vitro, indicating that BFP-3 could have potential applications in the treatment of ovarian cancer.