Preparation, chemical structure, and immunostimulatory activity of a water-soluble heteropolysaccharide from Suillus granulatus fruiting bodies

Xiong Gao; Ranhua Zeng; Chi-Tang Ho; Bin Li; Shaodan Chen; Chun Xiao; Huiping Hu; Manjun Cai; Zhongzheng Chen; Yizhen Xie; Qingping Wu

doi:10.1016/j.fochx.2022.100211

Preparation, chemical structure, and immunostimulatory activity of a water-soluble heteropolysaccharide from Suillus granulatus fruiting bodies

Food Chem X. 2022 Jan 15:13:100211. doi: 10.1016/j.fochx.2022.100211. eCollection 2022 Mar 30.

Authors

Xiong Gao¹, Ranhua Zeng², Chi-Tang Ho³, Bin Li^{2

4}, Shaodan Chen¹, Chun Xiao¹, Huiping Hu¹, Manjun Cai¹, Zhongzheng Chen^{2

4}, Yizhen Xie^{1

5}, Qingping Wu¹

Affiliations

¹ State Key Laboratory of Applied Microbiology Southern China, Guangdong Provincial Key Laboratory of Microbial Safety and Health, Institute of Microbiology, Guangdong Academy of Sciences, Guangzhou 510070, China.
² College of Food Science, South China Agricultural University, 483 Wushan Street, Tianhe District, Guangzhou 510642, China.
³ Department of Food Science, Rutgers University, 65 Dudley Road, New Brunswick, NJ 08901, USA.
⁴ Guangdong Provincial Key Laboratory of Nutraceuticals and Functional Foods, South China Agricultural University, Guangzhou 510642, China.
⁵ Guangdong Yuewei Biotechnology Co. Ltd., Zhaoqing 526000, China.

Abstract

A water-soluble heteropolysaccharide (SGP2-1) was purified from Suillus granulatus fruiting bodies by anion-exchange chromatography and gel permeation chromatography. The structural characteristics were analyzed by high-performance gel permeation chromatography, high-performance liquid chromatography, Fourier transform infrared spectroscopy, gas chromatography-mass spectrometry, and nuclear magnetic resonance spectroscopy. The immunostimulatory activity was investigated using RAW 264.7 macrophages. Results showed that SGP2-1 with weight average molecular weight of 150.75 kDa was composed of mannose, glucose, and xylose. The backbone of SGP2-1 was mainly composed of → 4)-α-Glcp-(1→, and the terminal group α-d-Glcp → was linked to the main chain by O-6 position. SGP2-1 could significantly enhance pinocytic capacity, reactive oxygen species production, and cytokines secretion. SGP2-1 exerted immunomodulatory effects through interacting with toll-like receptor 2, and activating mitogen-activated protein kinase, phosphatidylinositol-3-kinase/protein kinase B, and nuclear factor-kappa B signaling pathways. These findings indicated that SGP2-1 could be explored as a potential immunomodulatory agent for application in functional foods.

Keywords: 1H-1H COSY, 1H-1H correlation spectroscopy; ANOVA, Analysis of variance; Akt, Protein kinase B; CCK-8, Cell counting kit-8; D2O, Deuterium oxide; DCFH-DA, 2′,7′-Dichlorofluorescein diacetate; DEPT, Distortionless enhancement by polarization transfer; DMEM, Dulbecco’s modified Eagle’s medium; DPBS, Dulbecco’s phosphate-buffered saline; ELISA, Enzyme-linked immunosorbent assay; ERK, Extracellular signal-regulated kinase; FT-IR, Fourier transform infrared spectroscopy; GC-MS, Gas chromatography-mass spectrometry; HMBC, Heteronuclear multiple bond correlation; HPGPC, High-performance gel permeation chromatography; HPLC, High performance liquid chromatography; HSQC, Heteronuclear single quantum correlation; Heteropolysaccharide; IL-6, Interleukin-6; Immunomodulatory activity; IκBα, I kappa B alpha; JNK, c-Jun N-terminal kinase; LPS, Lipopolysaccharides; MAPKs, Mitogen-activated protein kinase; MCP-1, Monocyte chemoattractant protein-1; Mw, Weight average molecular weight; NF-κB, Nuclear factor-kappa B; NMR, Nuclear magnetic resonance; NO, Nitric oxide; PI3K, Phosphatidylinositol-3-kinase; PMP, 1-Phenyl-3-methyl-5-pyrazolone; RIPA, Radioimmunoprecipitation assay; ROS, Reactive oxygen species; RT-PCR, Reverse transcription-polymerase chain reaction; Structural characterization; Suillus granulatus; TLR2, Toll-like receptor 2; TLR4, Toll-like receptor 4; TNF-α, Tumor necrosis factor-α; iNOS, Inducible nitric oxide synthase.