International Journal of Molecular Medical Science, 2024, Vol.14, No.6, 342-354 http://medscipublisher.com/index.php/ijmms 345 triple-helix conformation, which is a key factor in their enhanced bioactivity. For instance, studies have shown that high molecular weight LBPs, such as those with an Mw of 46.239 kDa, exhibit greater antioxidant and immune-boosting capacities compared to lower molecular weight polysaccharides, such as those around 1.912 kDa. The triple-helix structure, often found in high molecular weight LBPs, is thought to contribute to better stability and stronger interactions with biological targets, which leads to enhanced bioactivity (Zeng et al., 2023). Additionally, different extraction and processing methods can significantly affect the molecular weight and, consequently, the bioactivity of LBPs. For example, degradation methods such as chemical modification with ascorbic acid and hydrogen peroxide have been used to reduce the molecular weight of LBPs from around 223.5 kDa to 64.3 kDa, enhancing their bioavailability without major alterations to their functional groups (Al-Wraikat et al., 2022). Despite the decrease in molecular weight, these LBPs retain their bioactivity, particularly in terms of antioxidant properties, but may exhibit reduced immunomodulatory effects. This demonstrates the fine balance between molecular weight and biological function, where higher molecular weights favor immunomodulatory and antioxidant activities, but smaller fractions may offer advantages in terms of absorption and bioavailability. Molecular weight also influences the branching patterns and monosaccharide composition of LBPs. High molecular weight LBPs, such as those with Mw over 40 kDa, typically exhibit more complex branching structures, which include β-D-galactopyranose (β-D-Galp) linkages and α-arabinofuranose (α-Araf) branches. These features are associated with the strong immune-stimulating and antioxidant properties of LBPs. Moreover, LBPs with complex branched structures tend to form stable conformations, such as triple-helix structures, which further enhance their biological functions by increasing molecular interactions and binding affinities with receptors on immune cells (Wu et al., 2021). Thus, the intricate relationship between molecular weight, structure, and bioactivity makes LBPs a highly versatile compound with diverse therapeutic potentials. 2.3 Effect of structure on bioactivity The bioactivity of Lycium barbarum polysaccharides (LBPs) is highly dependent on their structural features, such as molecular weight, branching patterns, glycosidic linkages, and functional groups. Research has shown that LBPs with a higher molecular weight tend to exhibit stronger antioxidant, immunomodulatory, and anti-inflammatory effects compared to their lower molecular weight counterparts. For instance, studies by Zeng et al. (2023) demonstrated that LBPs with a molecular weight of ~46.239 kDa displayed significantly higher oxygen radical absorbance capacity (ORAC) and superoxide dismutase (SOD) activity than lower molecular weight fractions (~1.912 kDa) (Zeng et al., 2023). This suggests that larger, more complex polysaccharide chains provide greater protection against oxidative stress, likely due to the increased stability of their three-dimensional structures, such as triple-helix formations. These triple-helix conformations, commonly found in high-molecular-weight LBPs, are thought to enhance biological interactions, leading to improved antioxidant and immunomodulatory responses. The branching patterns and glycosidic linkages of LBPs also play a critical role in determining their bioactivity. Polysaccharides with highly branched structures, especially those containing β-D-galactopyranose (β-D-Galp) and α-arabinofuranose (α-Araf) linkages, have been found to possess more potent biological activities. A study by Wu et al. (2021) highlighted that LBPs with more complex and branched structures, particularly those with 1,3-linked and 1,6-linked β-D-Galp residues, exhibited enhanced neuroprotective and antioxidative effects in vitro (Wu et al., 2021). Additionally, chemical modifications, such as sulfation, have been shown to increase bioactivity. For example, sulfated derivatives of LBPs have been found to improve their anti-angiogenic properties, further supporting the idea that structural variations, including branching complexity and functional group modifications, significantly enhance the therapeutic potential of LBPs (Zhou et al., 2018). These findings underscore the importance of structural features in optimizing the bioactivity of LBPs, making them highly adaptable for use in pharmaceutical and nutraceutical applications. 3 Antioxidant Mechanisms of Lycium Barbarum Polysaccharides 3.1 Free radical scavenging ability Lycium barbarum polysaccharides (LBPs) have been extensively studied for their potent free radical scavenging ability, which plays a critical role in mitigating oxidative stress. Free radicals such as reactive oxygen species
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