Dandan Ren

As dietary preferences diversify, aquatic foods remain a global staple, providing high-quality protein, essential fatty acids, and other essential nutrients. However, maintaining the quality and safety of seafood remains challenging. Salting is the primary postharvest processing method for the brown seaweed Undaria pinnatifida and can affect product quality and lead (Pb) accumulation. This study investigated changes in nutritional components, bioactive compounds, and Pb content throughout the harvest season and subsequent blanching and salting. Relationships among these variables were examined to identify suitable salting conditions. Samples were collected at nine 7-day intervals from the coastal waters of Dalian, China, and analyzed at the fresh, blanched, and salted stages. The maximum protein and alginate contents in fresh samples were 21.95% and 36.60% (dry weight), respectively, with a corresponding Pb content of 0.235 mg/kg. Principal component and Pearson correlation analyses showed that Pb accumulation was associated with protein and alginate contents. Salting with 40% salt for 48 h preserved favorable texture and color while maintaining Pb content below 0.35 mg/kg. These findings indicate that both harvest stage and processing affect nutritional quality and Pb levels. Although salting promotes Pb accumulation, controlling salt concentration and salting duration can limit this effect while preserving product quality. Salting with 40% salt for 48 h is therefore suggested as a suitable condition for producing salted U. pinnatifida with desirable texture, color, and Pb content. These findings provide a scientific basis for improving the quality and safety of salted brown algal products.

BACKGROUND: Aquatic products are highly valued for their rich nutrient content and unique flavors. However, they are particularly vulnerable to microbial contamination during transportation and storage, which can lead to spoilage. Fucoidan exhibited a broad spectrum of biological activities. Nevertheless, research on its application as an antifreeze agent remains limited. The practical application of high‐molecular‐weight fucoidan is constrained to some extent by its high viscosity and poor solubility. Conversely, low‐molecular‐weight fucoidan (WIF) prepared via physical, chemical, or enzymatic degradation methods may offer superior permeability and biological activities, making it a promising, novel, and highly efficient cryoprotectant. RESULTS: In this study, WIF was prepared through irradiation degradation using fucoidan as the material. The relative molecular weights of WIF obtained via 50 kGy γ‐ray irradiation ranged from 4.97 × 10 ³ to 3.25 × 10 ⁴ Da. It was found that the irradiation degradation method reduced the molecular weight and altered the original chemical composition. Following irradiation, the protein content decreased from 0.94% ± 0.02% to 0.24% ± 0.04%, whereas the reducing sugar content increased from 0.69% ± 0.01% to 6.25% ± 0.36%. Results indicated that soaking treatments with various concentrations of WIF solution exhibited excellent cryoprotective properties and water holding capacity in frozen Litopenaeus vannamei . Notably, after 180 days of frozen storage, the group treated with 15 g L ⁻¹ WIF maintained a myofibrillar protein Ca ²⁺ ‐ATPase activity of 0.0338 U mg ⁻¹ prot and a total sulfhydryl content of 30.06 μmol g ⁻¹ prot, both of which were significantly higher than those of the other groups ( P < 0.05). Furthermore, at day 180, the surface hydrophobicity of the 15 g L ⁻¹ WIF group was 61.35 μg mg ⁻¹ prot, significantly lower than that of the control groups ( P < 0.05). CONCLUSION: These findings demonstrate that WIF effectively inhibits the decline of Ca ²⁺ ‐ATPase activity, the oxidation of sulfhydryl groups, protein carbonylation, the exposure of hydrophobic residues, and the accumulation of malondialdehyde. In conclusion, WIF with lower molecular weight shows superior antifreeze and water retention abilities compared to high‐molecular‐weight fucoidan. © 2026 Society of Chemical Industry.

Ulcerative colitis (UC) is a form of inflammatory bowel disease (IBD), which is marked by severe abdominal pain, weight loss, perianal bleeding, and diarrhea. This study successfully isolated and purified four low-molecular-weight fucoidan oligosaccharides through acid hydrolysis and Bio Gel P10 gel filtration. The molecular weights were 2.9 × 10⁴–1.36 × 10⁵ Da, 182–1012 Da, 161–939 Da and 161–939 Da, respectively. A mouse model of colitis was induced using Dextran Sulfate Sodium (DSS). The results indicated that fucoidan and fucoidan oligosaccharides could ameliorate murine ulcerative colitis, with the oligosaccharides (200 mg/kg/d) demonstrating superior therapeutic effects. This superiority was likely attributed to the lower molecular weight and higher content of total sugars and fucose. The primary mechanisms involved the modulation of gene and protein expression levels associated with the Toll-like receptor 4, Myeloid differentiation primary response 88, nuclear factor kappa-light-chain-enhancer of activated B cells, p65, and Inhibitor of kappa light polypeptide gene enhancer in B cells, alpha (TLR4, MYD88, NF-κB p65, and IκB-α) signaling pathways, which reduce the production of inflammatory cytokines such as tumor necrosis factor-alpha, Interleukin-1 beta and Interleukin-6 (TNF-α, IL-1β, and IL-6). Additionally, these oligosaccharides alleviated oxidative stress, enhanced the levels of intestinal barrier proteins (Claudin family member 4 and Zonula occludens protein 1), regulated the abundance and diversity of the gut microbiota, and increased the levels of short-chain fatty acids (SCFAs) in the intestine. It is worth emphasizing that this study can only demonstrate that fucoidan oligosaccharides have a mitigating effect on intestinal inflammation in mice. Further research is needed in the future to investigate the structure–activity relationship of fucoidan oligosaccharides and their impact on human intestinal microbiota, in order to further elucidate their anti-inflammatory mechanisms.

The biological activities of fucoidan from brown algae have attracted considerable attention. Degradation to low-molecular-weight fucoidan reduces viscosity and improves bioavailability, enhancing antioxidant and anti-inflammatory effects. Fucoidan was degraded using acetic acid combined with ⁶⁰Co γ-ray irradiation and fractionated by Bio-Gel P10 chromatography to obtain four fractions (AIF1–AIF4). The fractions were structurally characterized and assessed for in vitro radical-scavenging activity and modulation of oxidative stress markers in H₂O₂-induced RAW264.7 macrophages. Compared with the model group, all fractions significantly increased catalase (CAT) and superoxide dismutase (SOD) activities, with the highest increase of approximately 1.33 U/mgprot for CAT and 20.32 U/mgprot for SOD, while decreasing malondialdehyde (MDA) and intracellular reactive oxygen species (ROS) levels. Among the four fractions, AIF4, with the lowest molecular weight, exhibited the highest antioxidant activity. LMWF treatment also upregulated the mRNA expression of antioxidant-related genes (HO-1, SOD1, SOD2) and signaling molecules (PI3K and Akt), accompanied by increased protein levels of nuclear factor erythroid 2-related factor 2 (Nrf2) and PI3K/Akt pathway components. These findings indicate that LMWF is closely associated with the regulation of the PI3K/Akt–Nrf2 signaling axis under oxidative conditions and support its potential application as a dietary antioxidant ingredient.

This study investigated how different extraction parts of raw materials and different flocculation methods affect the extraction yield, structure, and properties of sodium alginate. The aim was to improve the quality of sodium alginate and provide theoretical guidance for upstream enterprises. In this study, Lessonia nigrescens (LN) was used as a raw material. The alkali treatment conditions were optimized. The optimal extraction conditions were determined to be a 2% sodium carbonate concentration, a duration of 4 h, a material-to-liquid ratio of 1:40, and a temperature of 60 °C, achieving an extraction yield of 43.03%. LN was categorized into blades, stipes, holdfasts, and whole seaweed for comparative analysis, and sodium alginate was flocculated using the acid, calcium, and ethanol methods. Structural and physicochemical analyses showed that the mannuronic acid/guluronic acid (M/G) ratios of the twelve sodium alginate samples ranged from 5.73 to 8.76. The LN part had a greater influence on the M/G ratio than the flocculation method. The relative molecular weight (2343–3074 kDa) and viscosity (170–331 mPa·s) exhibited consistent trends. For the same part, the effect of the flocculation method on the molecular weight followed the order ethanol > acid > calcium. The physicochemical properties of the extracted sodium alginate met the requirements specified in the physicochemical index standard GB 1886.243-2016 of China.

To investigate the effects of different processing methods on the characteristic flavor of Undaria pinnatifida, this study systematically compared the volatile flavor compositions of four sample groups, namely fresh U. pinnatifida from Dalian (WD), salted U. pinnatifida from Dalian (WY), dried U. pinnatifida from Dalian (WG), and fresh U. pinnatifida from Shantou (WS), using GC-IMS, combined with relative odor activity value (ROAV) analysis. The results showed that GC-IMS effectively distinguished the volatile profiles of samples subjected to different processing methods, identifying a total of 45 flavor compounds. Aldehydes emerged as the key flavor components, accounting for relative contents of 53.85% (WD), 41.12% (WY), 52.62% (WG), and 45.28% (WS), which were significantly higher than those of other compound classes. The ROAV analysis revealed that 1-octen-3-ol and 1-octen-3-one were the characteristic compounds shared by all four sample groups. Furthermore, distinct processing methods influenced the distribution of saturated aldehydes, esters, and furans, which could serve as key indicators to distinguish between different processing techniques. Multidimensional analysis, including GC-IMS fingerprint visualization and principal component cluster analysis, confirmed significant flavor differences among the samples from different processing methods and origins. This study provides a theoretical basis for the quality control and standardized production of algal-based foods by multidimensionally analyzing flavor evolution in U. pinnatifida during processing.

Anti‐aging research represents a significant and challenging frontier in biomedical science. While rhodoxanthin, a naturally occurring carotenoid, has demonstrated preliminary antioxidant properties, its precise antiaging mechanisms remain poorly understood. This study systematically investigated the antiaging effects of rhodoxanthin in a D‐galactose‐induced murine aging model with particular focus on elucidating its underlying molecular mechanisms. Our findings revealed that rhodoxanthin administration significantly attenuated oxidative damage in both brain and liver tissues, as evidenced by reduced lipid peroxidation and enhanced activities of key antioxidant enzymes. At the optimal dosage (80 mg/kg rhodoxanthin), antioxidant enzyme activities were restored to 84.3% (CAT), 66.7% (SOD), and 145% (GPX) of model control levels in the liver and 61.36% (CAT), 4.2% (SOD), and 22.2% (GPX) in the brain. Mechanistic studies indicated that rhodoxanthin's antiaging effects were mediated through modulation of the nuclear factor erythroid‐related factor Nrf2 and PI3K/Akt signaling pathways. Quantitative analysis demonstrated significant upregulation of Nrf2, PI3K, and Akt expression in both hepatic and cerebral tissues of aging mice, and behavioral assessments confirmed that rhodoxanthin not only served as a potent natural antioxidant but also improved memory retention and cognitive function in aged subjects. These results collectively established rhodoxanthin as food‐functional component, with dual protective effects against both oxidative damage and cognitive decline. Rhodoxanthin could be used as a natural antioxidant in the food industry.

Fucoxanthin (Fx), a natural carotenoid predominantly found in brown algae and certain microalgae, has garnered significant attention in recent years for its potent antioxidant and anti-inflammatory properties. As inflammation and oxidative stress represent fundamental physiological responses that play pivotal roles in disease pathogenesis, their intricate interplay has become a focus of scientific investigation. This study employed an LPS-induced THP-1 cell inflammation model to elucidate the anti-inflammatory mechanisms of fucoxanthin and its interaction with oxidative stress pathways. Our findings demonstrate that fucoxanthin effectively suppresses the LPS-induced secretion of pro-inflammatory mediators, including IL-1β, IL-6, iNOS, COX-2, and TNF-α, in THP-1 cells. Mechanistically, this effect is achieved through the inhibition of IκB-α phosphorylation, thereby blocking the activation of the NF-κB p65 signaling pathway. Concurrently, fucoxanthin exhibits robust antioxidant activity, as evidenced by enhanced catalase (CAT) and superoxide dismutase (SOD) activities coupled with reduced malondialdehyde (MDA) production. Furthermore, fucoxanthin activates the Nrf2 signaling pathway, leading to upregulated heme oxygenase-1 (HO-1) expression and the consequent attenuation of reactive oxygen species (ROS) generation. These results collectively indicate that fucoxanthin exerts dual protective effects through anti-inflammatory action mediated by NF-κB pathway inhibition and antioxidant activity via Nrf2/HO-1 pathway activation. The observed crosstalk between these pathways suggests that fucoxanthin’s therapeutic potential stems from its ability to simultaneously modulate interconnected inflammatory and oxidative stress responses. Our study provides compelling evidence that fucoxanthin’s antioxidant and anti-inflammatory activities are functionally interrelated, with the Nrf2 signaling pathway serving as a critical node in this protective mechanism against LPS-induced cellular damage.