- Polysaccharides, long-chain carbohydrates composed of monosaccharide units linked by glycosidic bonds, are among the most structurally diverse and functionally important biomolecules in nature. Found in plants, fungi, bacteria, algae, and animals, polysaccharides serve as structural components (e.g., cellulose, chitin), energy storage molecules (e.g., starch, glycogen), and mediators of biological recognition (e.g., glycosaminoglycans in the extracellular matrix). Beyond their fundamental physiological roles, polysaccharides have attracted great interest for their biological and pharmacological activities, which make them valuable in medicine, biotechnology, and nutrition.
- From a biological perspective, polysaccharides interact with cells, proteins, and signaling pathways, often acting as modulators of immunity, oxidative stress, or microbial activity. Many naturally derived polysaccharides demonstrate immunomodulatory properties, enhancing both innate and adaptive immune responses. For instance, β-glucans from fungi and cereals stimulate macrophages, natural killer cells, and dendritic cells, improving host defense mechanisms against infections and tumors. Similarly, sulfated polysaccharides from algae, such as fucoidans, influence cytokine production and complement activation, highlighting their role in immunoregulation.
- Polysaccharides also exhibit strong antioxidant activity, protecting cells and tissues from oxidative stress by scavenging free radicals, chelating transition metals, and enhancing endogenous antioxidant enzymes. This property is particularly relevant in mitigating chronic diseases such as cardiovascular disorders, diabetes, neurodegeneration, and cancer, where oxidative damage contributes to pathogenesis. In addition, polysaccharides can exert antimicrobial effects, either directly by disrupting microbial membranes and inhibiting biofilm formation or indirectly by enhancing host immune defense against bacterial, viral, and fungal pathogens.
- The pharmacological activities of polysaccharides are broad and diverse, encompassing anticancer, antidiabetic, anti-inflammatory, anticoagulant, hypolipidemic, and hepatoprotective effects. For example, heparin and heparan sulfate are clinically established anticoagulant polysaccharides, widely used to prevent and treat blood clots. Fucoidans and laminarins from marine algae show promising anticancer activities by inducing apoptosis, suppressing angiogenesis, and modulating tumor immunity. Plant-derived polysaccharides, such as pectins and arabinogalactans, have been reported to regulate gut microbiota and improve metabolic health, including glucose and lipid metabolism, making them candidates for managing diabetes and obesity. Furthermore, chitosan and its derivatives have demonstrated wound-healing, antimicrobial, and cholesterol-lowering properties, supporting their use in biomedical and nutraceutical applications.
- Another important aspect of polysaccharides lies in their prebiotic effects. Non-digestible polysaccharides, such as inulin, resistant starch, and certain hemicelluloses, promote the growth of beneficial gut microbiota like Bifidobacterium and Lactobacillus. This microbial modulation improves gut barrier function, enhances short-chain fatty acid production, and contributes to systemic health benefits, including improved immunity, reduced inflammation, and protection against metabolic disorders. Thus, polysaccharides act as functional food components, bridging nutrition and pharmacology.
- From a therapeutic standpoint, polysaccharides are often regarded as biocompatible, biodegradable, and low in toxicity, making them attractive scaffolds for drug delivery and biomedical engineering. Their chemical versatility allows modifications such as sulfation, carboxymethylation, or acetylation, which can enhance biological activities or improve pharmacokinetic properties. For instance, sulfated derivatives of natural polysaccharides often exhibit stronger antiviral or anticoagulant effects. Advances in nanotechnology have also enabled the development of polysaccharide-based nanoparticles, hydrogels, and conjugates for targeted delivery of drugs, proteins, and nucleic acids.
Polysaccharides by Pharmacological Activity
Immunomodulatory & Immunostimulant
- β-Glucan (fungi, yeast, cereals) – activates macrophages, dendritic cells, NK cells; enhances host defense.
- Fucoidan (brown algae) – regulates cytokine production, immune cell activation.
- Laminarin (brown algae) – enhances immune responses, supports anti-tumor activity.
- Arabinogalactan (larch trees, medicinal plants) – stimulates immune system and gut health.
- Scleroglucan (fungi) – immune-enhancing and antioxidant effects.
- Peptidoglycan (bacterial cell walls) – activates innate immune receptors (e.g., TLR2).
- Capsular polysaccharides (bacteria like S. pneumoniae) – immunogenic, basis for vaccines.
Antioxidant
- Fucoidan (brown algae) – scavenges free radicals, reduces oxidative stress.
- Laminarin (brown algae) – antioxidant, cytoprotective effects.
- Chitosan (crustacean shells, fungi) – antioxidant, enhances tissue repair.
- Dextran (bacterial origin) – protects cells against oxidative damage.
- Pullulan (fungi) – antioxidant, prevents oxidative degradation in foods/pharma.
- Scleroglucan (fungi) – antioxidant protection.
- Pectin (fruits) – reduces oxidative stress, supports metabolic health.
Antimicrobial & Antiviral
- Chitosan – antibacterial (cell wall disruption), antifungal, antiviral.
- Fucoidan – antiviral (e.g., against HIV, influenza, herpes), antimicrobial.
- Carrageenan (red algae) – antiviral (used in some nasal sprays against respiratory viruses).
- Pullulan – antimicrobial, biofilm-inhibitory effects.
- Xanthan gum – antimicrobial and immunomodulatory potential.
Anticancer
- β-Glucan – stimulates anti-tumor immune responses.
- Fucoidan – induces apoptosis, inhibits angiogenesis and metastasis.
- Laminarin – anticancer through apoptosis induction and immune support.
- Arabinogalactan – supports anti-tumor immunity, synergistic with chemotherapy.
- Pectin – inhibits cancer cell adhesion and metastasis.
- Scleroglucan – reported anti-tumor activity in experimental models.
Cardiovascular & Metabolic Health
- Chitosan – lowers cholesterol and triglycerides.
- β-Glucan – reduces cholesterol, improves glycemic control.
- Pectin – lowers cholesterol and regulates glucose absorption.
- Inulin – improves lipid metabolism, regulates blood sugar.
- Dextran – used as plasma expander, supports cardiovascular stability.
Anticoagulant & Blood-related
- Heparin – gold standard anticoagulant in clinical medicine.
- Heparan sulfate – modulates coagulation and angiogenesis.
- Dermatan sulfate – anticoagulant, promotes wound repair.
- Chondroitin sulfate – mild anticoagulant effects, cartilage protection.
- Fucoidan – anticoagulant and antithrombotic activities.
- Carrageenan – anticoagulant activity (structure-dependent).
Wound Healing & Tissue Engineering
- Chitosan – promotes wound healing, antimicrobial protection.
- Alginate – forms hydrogels for wound dressings, promotes healing.
- Hyaluronic acid – tissue hydration, wound repair, joint therapy.
- Dextran – used in hydrogels for wound care and drug delivery.
Prebiotic & Gut Health
- Inulin (chicory root, Jerusalem artichoke) – promotes Bifidobacterium, SCFA production.
- Pectin – improves gut microbiota composition and bowel health.
- Arabinogalactan – prebiotic, supports gut and liver health.
- Alginate – prebiotic activity, modulates gut microbiota.
- Xanthan gum – supports gut health, used as dietary fiber.
