The marine acid polysaccharide fucoidan has attracted attention from both the food and pharmaceutical industries due to its promising therapeutic effects. Fucoidan is a polysaccharide that mainly consists of L-fucose and sulphate groups. Its excellent biological function is attributed to its unique biological structure. Classical activities include antitumor, antioxidant, anticoagulant, antithrombotic, immunoregulatory, antiviral and anti-inflammatory effects. More recently, fucoidan has been shown to alleviate metabolic syndrome, protect the gastrointestinal tract, benefit angiogenesis and bone health. This review focuses on the progress in our understanding of the biological activities of fucoidan, highlighting its benefits for the treatment of human disease. We hope that this review can provide some theoretical basis and inspiration for the product development of fucoidan.

Alginate is a natural polysaccharide present in various marine brown seaweeds. Alginate oligosaccharide (AOS) is a degradation product of alginate, which has received increasing attention due to its low molecular weight and promising biological activity. The wide-ranging biological activity of AOS is closely related to the diversity of their structures. AOS with a specific structure and distinct applications can be obtained by different methods of alginate degradation. This review focuses on recent advances in the biological activity of alginate and its derivatives, including their anti-tumor, anti-oxidative, immunoregulatory, anti-inflammatory, neuroprotective, antibacterial, hypolipidemic, antihypertensive, and hypoglycemic properties, as well as the ability to suppress obesity and promote cell proliferation and regulate plant growth. We hope that this review will provide theoretical basis and inspiration for the high-value research developments and utilization of AOS-related products.2 of 26 the 4 C 1 conformation and are linked by β-1,4-glycosidic bond, while in pG, all G residues are in the 1 C 4 conformation and are linked by an α-1,4-glycosidic bond. These features are responsible for the differences in their higher-order structure. For example, pG exhibits an egg-box-like conformation and usually forms stiffer 2-fold screw helical chains when dissolved in water, while pM forms belt chains through intra-molecular hydrogen bonds. Due to these dissimilarities, pM and pG, as well as their derivatives, will exhibit different activities [12].As the most abundant marine biomass and low-cost material, alginate has been extensively used in the food and medical industries. The widespread utilization is also driven by its favorable chemical properties and versatile activities. However, the applications of alginate have been greatly limited due to its high molecular weight and low bioavailability. Therefore, the degradation of high molecular weight polysaccharides into low molecular weight poly-or oligosaccharides is considered of great significance for improving their bioavailability, increasing the body's absorption of drugs, and fully utilizing the efficacy of polysaccharides. Recently, the degradation products of alginate, i.e., alginate oligosaccharides (AOS), have attracted increasing attention due to their biological activities and excellent solubility in water [13]. AOS can be depolymerized by different degradation methods, including enzymatic degradation, acid hydrolysis, and oxidative degradation [14]. Alginate lyases have been isolated from a wide range of organisms, including algae, marine invertebrates, and marine and terrestrial microorganisms, which can degrade alginate into unsaturated oligosaccharides by β-elimination [15,16]. Moreover, due to differences in degradation patterns, G content (G/M ratio), molecular weight, and spatial conformation of degradation products, AOS possess a variety of biological activities. They have anti-tumor properties [17], counteract oxidation [8], regulate immune respo...

Fucoxanthin is a natural carotenoid derived mostly from many species of marine brown algae. It is characterized by small molecular weight, is chemically active, can be easily oxidized, and has diverse biological activities, thus protecting cell components from ROS. Fucoxanthin inhibits the proliferation of a variety of cancer cells, promotes weight loss, acts as an antioxidant and anti-inflammatory agent, interacts with the intestinal flora to protect intestinal health, prevents organ fibrosis, and exerts a multitude of other beneficial effects. Thus, fucoxanthin has a wide range of applications and broad prospects. This review focuses primarily on the latest progress in research on its pharmacological activity and underlying mechanisms.

Atherosclerosis is a chronic disease characterized by lipid accumulation and chronic inflammation of the arterial wall, which is the pathological basis for coronary heart disease, cerebrovascular disease and thromboembolic disease. Currently, there is a lack of low-cost therapeutic agents that effectively slow the progression of atherosclerosis. Therefore, the development of new drugs is urgently needed. The research and development of marine-derived drugs have gained increasing interest from researchers across the world. Many marine organisms provide a rich material basis for the development of atherosclerotic drugs. This review focuses on the latest technological advances in the structures and mechanisms of action of marine-derived anti-atherosclerotic substances and the challenges of the application of these substances including marine polysaccharides, proteins and peptides, polyunsaturated fatty acids and small molecule compounds. Here, we describe the theoretical basis of marine biological resources in the treatment of atherosclerosis.

Detailed knowledge of the intestinal transport of polymannuronic acid (PM) and polyguluronic acid (PG) is critical for understanding their biological activities. To investigate the transport in the gastrointestinal tract, PM and PG were chemically modified with tyramine and conjugated with fluorescein isothiocyanate (FITC) to synthesize FITC-PM (F-PM) and FITC-PG (F-PG) successfully. The transport mechanisms of F-PM and F-PG across the intestinal epithelial cell monolayers (Caco-2 cell monolayers) were then investigated. The results demonstrated that the transport of F-PM and F-PG into epithelial cells was time- and energy-dependent, which was mediated by the macropinocytosis pathway and the clathrin- and caveolae (or lipid raft)-mediated endocytic pathway. The transport process of F-PM and F-PG in Caco-2 cells depended on the acidification of endosomes and involved lysosomes. Tubulin mediated the transport of F-PM, but not of F-PG. Moreover, the absorption enhancer chitosan (CS) promoted the transport of F-PM and F-PG, increasing the apparent permeability coefficient (Papp) by 1.9-fold and 2.6-fold, respectively, by reversibly opening the tight junction (TJ). In summary, this study provided a comprehensive understanding of the transport of PM and PG in the small intestinal epithelial cells, which will provide a theoretical basis for the development of PM and PG with good intestinal absorption.

Fucoidan has a variety of pharmacological activities, but the understanding of the mechanism of fucoidan-induced apoptosis of colorectal cancer cells remains limited. The results of the present study demonstrated that the JNK signaling pathway is involved in the activation of apoptosis in colorectal cancer-derived HT-29 cells, and fucoidan induces apoptosis by activation of the DR4 at the transcriptional and protein levels. The survival rate of HT-29 cells was approximately 40% in the presence of 800 μg/mL of fucoidan, but was increased to 70% after DR4 was silenced by siRNA. Additionally, fucoidan has been shown to reduce the mitochondrial membrane potential and destroy the integrity of mitochondrial membrane. In the presence of an inhibitor of cytochrome C inhibitor and DR4 siRNA or the presence of cytochrome C inhibitor only, the cell survival rate was significantly higher than when cells were treated with DR4 siRNA only. These data indicate that both the DR4 and the mitochondrial pathways contribute to fucoidan-induced apoptosis of HT-29 cells, and the extrinsic pathway is upstream of the intrinsic pathway. In conclusion, the current work identified the mechanism of fucoidan-induced apoptosis and provided a novel theoretical basis for the future development of clinical applications of fucoidan as a drug.

With twice the number of cancer’s deaths, cardiovascular diseases have become the leading cause of death worldwide. Atherosclerosis, in particular, is a progressive, chronic inflammatory cardiovascular disease caused by persistent damage to blood vessels due to elevated cholesterol levels and hyperlipidemia. This condition is characterized by an increase in serum cholesterol, triglycerides, and low-density lipoprotein, and a decrease in high-density lipoprotein. Although existing therapies with hypolipidemic effects can improve the living standards of patients with cardiovascular diseases, the drugs currently used in clinical practice have certain side effects, which insists on the need for the development of new types of drugs with lipid-lowering effects. Some marine-derived substances have proven hypolipidemic activities with fewer side effects and stand as a good alternative for drug development. Recently, there have been thousands of studies on substances with lipid-lowering properties of marine origin, and some are already implemented in clinical practice. Here, we summarize the active components of marine-derived products having a hypolipidemic effect. These active constituents according to their source are divided into algal, animal, plant and microbial and contribute to the development and utilization of marine medicinal products with hypolipidemic effects.

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