Acetylation Modification, Characterization, and Anticomplementary Activity of Polysaccharides from Rhododendron dauricum Leaves

Abstract

This study focuses on the acetylation modification of polysaccharides from Rhododendron dauricum leaves (RDPs) with a high degree of substitution (DS) and then discusses their characterization and biological activity. The optimum acetylation conditions of RDPs were optimized by response surface methodology, which were reaction time 3 h, reaction temperature 50 °C, and the liquid-solid ratio 16 mL/g. Under the optima schemes, two eco-friendly acetylated polysaccharides from R. dauricum leaves (AcRDP-1 with DS of 0.439 ± 0.025 and AcRDP-2 with DS of 0.445 ± 0.022) were prepared. The results of structural characterization showed that the AcRDP-1 (9.3525 × 103 kDa) and AcRDP-2 (4.7016 × 103 kDa) were composed of mannose, glucose, galactose, and arabinose with molar ratios of 1.00:5.01:1.17:0.15 and 1.00:4.47:2.39:0.88, respectively. Compared with unmodified polysaccharides, the arabinose content and molecular weight of the two acetylated polysaccharides decreased, and their triple helix conformation disappeared, and further improved their anticomplementary activity. The two acetylated polysaccharides showed stronger a complement inhibition effect than the positive drug by blocking C2, C3, C4, C5, C9, and factor B targets in the classical and alternative pathways. This research indicated that acetylation modification could effectively enhance the anticomplementary activity of RDPs, which is beneficial for the development and utilization of R. dauricum leaves.

Enhancement of physicochemical properties, antioxidant, antitumor, and anticoagulant activities via acetylation of Hypsizygus ulmarius polysaccharide

“…The enhanced absorption peak at about 1245 cm −1 corresponds to the asymmetric stretching vibration of C‐O‐C bonds in the carbonyl group. The peak falls at 1740 cm −1 was attributed to the vibration of C=O of O ‐acetyl group, demonstrating the success of the acetylated polysaccharide modification (Xie et al ., 2015; Hu et al ., 2022). HUP1 and Ac‐HUP1 are pyranose forms of carbohydrates, as evidenced by the absorptions at 1148 cm −1 and 1073/1070 cm −1 (Zhao et al ., 2005; Yang & Zhang, 2009).…”

Chemical Modification of Polysaccharides: A Review of Synthetic Approaches, Biological Activity and the Structure–Activity Relationship

“…Then, acetic anhydride is added, and NaOH is continued to maintain the pH value at 8–10 for a period of the reaction. Finally, HCl reagent is added to adjust the solution to being neutral, and acetylated polysaccharides are dialyzed to remove reaction by-products, and their concentration increased [ 28 ]. There are a lack of corresponding experiments for this phenomenon to clarify the relationship between the addition of catalysts and the degree of acetylation substitution.…”

Relationship of Gene-Structure–Antioxidant Ability of Exopolysaccharides Derived from Lactic Acid Bacteria: A Review

“…66 However, further research is needed on the acetyl group substitution sites and the structure−activity relationships of acetylated EPS. 73 Enzymatic Modification. Several enzymes are involved in the biosynthesis of EPS.…”

“…The degree of acetylation substitution is dependent on the reaction conditions including reaction time, temperature, and the amount of acetylated reagent. Acetylated EPS with different DS show distinct molar ratios of monosaccharides and varying degrees of biological activity. , When EPS derived from Lactobacillus helveticus MB2-1 are chemically acetylated under suitable conditions, the acetylated EPS show stronger DPPH radical and superoxide anion scavenging ability and superior chelating activity of metal ion due to the substitution and altered structure . However, further research is needed on the acetyl group substitution sites and the structure–activity relationships of acetylated EPS …”