- Polysaccharides have emerged as an important class of natural antioxidants, attracting considerable interest due to their biocompatibility, biodegradability, and broad pharmacological potential. Unlike small-molecule antioxidants such as vitamins C and E, polysaccharides exert their effects through multifaceted mechanisms, including direct radical scavenging, chelation of transition metals, regulation of oxidative enzymes, and enhancement of endogenous antioxidant defenses. Their antioxidant potential is closely related to structural characteristics such as monosaccharide composition, glycosidic linkages, branching degree, molecular weight, and chemical modifications like sulfation, acetylation, or carboxymethylation.
- The mechanisms of antioxidant action of polysaccharides are diverse. Many can directly scavenge free radicals such as hydroxyl, superoxide, and DPPH radicals, thereby reducing oxidative stress at the molecular level. Others exhibit metal-chelating abilities, binding to pro-oxidant ions like Fe²⁺ and Cu²⁺, which catalyze the formation of reactive oxygen species (ROS) through Fenton-type reactions. Polysaccharides also modulate antioxidant enzyme systems, enhancing the activity of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px). In addition, some polysaccharides increase intracellular levels of reduced glutathione (GSH), a vital antioxidant molecule that maintains cellular redox balance.
- Plant-derived polysaccharides, such as pectin, arabinogalactan, and inulin, are known for their antioxidant properties. Pectins, rich in galacturonic acid residues, not only scavenge free radicals but also support gut health, indirectly reducing systemic oxidative stress. Marine polysaccharides such as fucoidan, laminarin, and carrageenan demonstrate particularly strong antioxidant activities due to their sulfated groups, which enhance radical scavenging and electron-donating abilities. Fucoidan, for example, has been shown to reduce lipid peroxidation, protect DNA from oxidative damage, and regulate antioxidant signaling pathways like Nrf2/ARE.
- Fungal polysaccharides, including β-glucans, lentinan, and scleroglucan, also play a significant role in antioxidant defense. β-glucans, in addition to immunomodulation, are effective in reducing oxidative stress by scavenging free radicals and stimulating antioxidant enzyme systems. Lentinan from shiitake mushrooms and scleroglucan from fungi exhibit protective effects against oxidative stress-induced cellular injury, making them promising in both functional foods and adjunct therapies. Similarly, bacterial polysaccharides like dextran and xanthan gum have been investigated for their radical scavenging and protective properties in oxidative stress-related conditions.
- Chemical modifications of polysaccharides can enhance their antioxidant properties. For instance, sulfated, phosphorylated, or carboxymethylated derivatives often exhibit significantly higher radical scavenging capacity compared to their native forms. These modifications increase electron-donating capacity, solubility, and interaction with free radicals, making modified polysaccharides attractive for pharmaceutical and nutraceutical development.
- From a pharmacological perspective, polysaccharide antioxidants have potential in preventing or managing oxidative stress-related diseases, including cardiovascular disorders, diabetes, neurodegeneration, liver injury, and cancer. Their ability to modulate oxidative pathways also contributes to anti-aging effects and skin protection, explaining their use in cosmetics and dermatological formulations. In addition, polysaccharide-based antioxidants have applications in food preservation, where they can inhibit lipid oxidation and prolong shelf life.
