- Polysaccharides are increasingly recognized as potent antiviral agents, offering both direct and indirect mechanisms of defense against a wide range of viruses. Their structural diversity, biodegradability, and low toxicity make them attractive alternatives or adjuncts to conventional antiviral drugs. Many polysaccharides act by directly interfering with viral life cycles, such as blocking viral attachment, entry, or replication, while others stimulate host immune responses, enhancing the body’s natural antiviral defenses. Structural modifications—particularly sulfation, acetylation, or phosphorylation—can greatly enhance their antiviral potency, making them a promising field of study in both medicine and biotechnology.
- One of the most widely studied groups of antiviral polysaccharides is the sulfated polysaccharides from marine algae, including fucoidan (brown algae), carrageenan (red algae), and ulvan (green algae). These polysaccharides possess abundant negatively charged sulfate groups, which mimic host cell surface glycosaminoglycans used by many viruses for initial attachment. By binding to viral envelope glycoproteins, they prevent viruses such as HIV, herpes simplex virus (HSV), human papillomavirus (HPV), influenza, and coronaviruses from attaching to and entering host cells. For example, carrageenan has been successfully formulated into nasal sprays and topical gels that block respiratory and sexually transmitted viral infections.
- Beyond marine polysaccharides, fungal and plant polysaccharides also exhibit antiviral activities, often by modulating host immunity. β-glucans, lentinan (from shiitake mushrooms), and arabinogalactans stimulate macrophages, dendritic cells, and natural killer (NK) cells, enhancing the production of antiviral cytokines such as interferons (IFNs). This indirect mechanism boosts the host’s resistance to viral infections and may reduce viral replication. Similarly, polysaccharides like pectin derivatives and hemicelluloses have shown protective effects against viral infections through immunomodulation and antioxidant activity.
- Chitosan and its derivatives represent another class of antiviral polysaccharides. While native chitosan has limited direct antiviral activity, its sulfated or quaternized derivatives display strong antiviral properties. Sulfated chitosan, for example, has shown inhibitory effects against HIV, influenza, and hepatitis viruses by blocking viral adsorption and replication. Chitosan-based nanoparticles have also been developed as antiviral drug delivery systems, improving the stability and controlled release of antiviral compounds.
- The mechanisms of antiviral activity of polysaccharides can be summarized as:
- Blocking viral adsorption and entry by competing with host cell receptors.
- Inhibiting viral replication within host cells through interaction with viral enzymes or nucleic acids.
- Modulating the host immune system, enhancing production of interferons and other antiviral cytokines.
- Acting as carriers for antiviral drugs or vaccines, improving efficacy and bioavailability.
- From an application perspective, antiviral polysaccharides are being developed for use in pharmaceuticals, nutraceuticals, functional foods, and biomedical devices. Carrageenan-based nasal sprays are already available for preventing common cold viruses. Fucoidan and other marine polysaccharides are included in dietary supplements for immune support. In addition, polysaccharide-based hydrogels, coatings, and nanoparticles are being explored as delivery systems for antiviral therapies and vaccines.
