Structural Characterization and Immunomodulatory Activity of an Acidic Polysaccharide from Rhodomyrtus tomentosa
Huihui Yin1,2, Guoqing Yan1,2, Yunfu Huang1,2
1Guangxi Key Laboratory of Veterinary Biotechnology, Guangxi Veterinary Research Institute, Nanning 530001, China.
Abstract:
A polysaccharide from Rhodomyrtus tomentosa (Aiton) Hassk. fruit (RTFP-2b) was isolated and purified. RTFP-2b has a molecular weight of 22.995 kDa and consists of nine monosaccharides, with arabinose (38.68%), galactose (21.86%), and galacturonic acid (14.83%) as its major components. Methylation and NMR analyses revealed dominant glycosidic linkages, including α-L-Araf-(1→, →4)-α-D-GalpA-(1→, →4)-α-D-Galp-(1→, →5)-α-L-Araf-(1→, →3)-α-L-Araf-(1→, →2)-α-L-Rhap-(1→, and →3,4,6)-β-D-Galp-(1→. Bioactivity assays using lipopolysaccharide (LPS)-stimulated RAW264.7 cells showed that RTFP-2b exhibits dose-dependent immunomodulatory properties. When administered at lower concentrations (100-200 μg/mL), RTFP-2b enhanced phagocytosis and IL-1β production. At higher concentrations (300-400 μg/mL), it significantly suppressed nitric oxide and showed biphasic regulation of IL-1β, but unexpectedly increased IL-6 levels in LPS-stimulated RAW264.7 cells. These immunomodulatory effects of RTFP-2b at higher doses were accompanied by inhibition of NF-κB signaling. These findings indicate that RTFP-2b is a structurally distinct acidic polysaccharide with dose-dependent immunomodulatory properties, suggesting its potential application in functional foods or pharmaceuticals.
