Medicinal Plant Research 2024, Vol.14, No.6, 358-370 http://hortherbpublisher.com/index.php/mpr 360 Previous animal experiments have shown that Cordyceps polysaccharides can inhibit tumor cell proliferation, induce cell apoptosis, and regulate immune responses in tumor-bearing models. These results support the potential application of Cordyceps polysaccharides as natural anti-tumor active substances and functional food ingredients (Xu et al., 2021; Dai et al., 2024a). 3 Chemical Modification Strategies for Cordyceps Polysaccharides 3.1 Sulfation, phosphorylation, and carboxymethylation of Cordyceps polysaccharides Sulfonation, phosphorylation and carboxymethylation are the most commonly studied chemical modification methods for Cordyceps polysaccharides, which change the physicochemical properties and biological activities of native polysaccharides by introducing specific functional groups. These methods each use different reagents and reaction conditions. Sulfonation usually uses the chlorosulfonic acid-pyridine method to introduce sulfonic acid groups into the polysaccharide backbone, and the modification effect can be confirmed by chemical analysis and infrared spectroscopy (IR) (Jing et al., 2015). Phosphorylation is often carried out using phosphoric acid or phosphorus oxychloride, while carboxymethylation is completed using monosodium chloroacetate under alkaline conditions (Xie et al., 2020; Zhao et al., 2023). These reactions mainly act on the hydroxyl groups of sugar residues to produce derivatives with a high degree of substitution and altered molecular conformation. After the introduction of sulfonic acid, phosphate or carboxyl groups, the polysaccharide chains gain enhanced water solubility and impart negative charges to them, thereby improving their dispersibility and ability to interact with biological targets (Xie et al., 2020; Zhao et al., 2023). For example, sulfonated Cordyceps polysaccharides have higher solubility and stronger antitumor activity than unmodified forms, and the optimal degree of sulfonation (DS 1.2-1.5) is positively correlated with in vitro antitumor effects (Jing et al., 2015). Carboxylmethylation and phosphorylation can also improve their solubility and may enhance their biological activity by promoting cellular uptake and enhancing immunomodulatory effects. 3.2 Acetylation and selenization of Cordyceps polysaccharides Acetylation is the process of introducing an acetyl group, usually at the C-2, C-3 or C-6 position of the sugar residue, with acetic anhydride or acetic acid as the reaction reagent (Zhao et al., 2023). Selenization, as a newer modification method, introduces selenium into the polysaccharide structure through biotransformation or reaction with sodium selenite to produce selenium-rich polysaccharide derivatives (Liu et al., 2017; Sun et al., 2018; Zhang et al., 2023). The success of these modifications can be confirmed by nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR) and elemental analysis, thereby revealing the introduction of new functional groups and changes in molecular conformation (Sun et al., 2018; Zhao et al., 2023; Zhang et al., 2023). Both acetylation and selenization can significantly affect the biological activity of Cordyceps polysaccharides. In particular, selenized derivatives show enhanced antitumor effects, such as inducing cancer cell apoptosis through mitochondrial pathways and death receptor-mediated pathways, while their antioxidant capacity is also significantly improved (Liu et al., 2017; Sun et al., 2018; Zhang et al., 2023). Acetylation may also modulate its antioxidant activity, although its effect depends on the degree of substitution and the different substitution sites (Zhao et al., 2023). These two modifications generally improve free radical scavenging ability, enhance immune activation, and more effectively inhibit tumor cell proliferation (Zhao et al., 2023; Zhang et al., 2023). 3.3 Grafting and nanoparticle-based modifications of Cordyceps polysaccharides Grafting and conjugation strategies refer to the covalent attachment of bioactive molecules or drugs to Cordyceps polysaccharides to construct derivatives with multiple functions to enhance their therapeutic potential (Guan et al., 2020; Wang et al., 2024). For example, acetic acid-modified Cordyceps polysaccharides can be made into nanoparticles for encapsulation and delivery of docetaxel, which has shown advantages in drug loading rate, sustained release performance and anti-tumor effect compared with traditional drug formulations (Guan et al., 2020). Such modifications can also be further integrated with targeting ligands or imaging probes to expand the application range of Cordyceps polysaccharides in drug delivery systems (Wang et al., 2024).
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