Elsevier

Carbohydrate Polymers

Volume 246, 15 October 2020, 116532
Carbohydrate Polymers

Structural elucidation, anti-inflammatory activity and intestinal barrier protection of longan pulp polysaccharide LPIIa

https://doi.org/10.1016/j.carbpol.2020.116532Get rights and content

Highlights

  • LPIIa, an active polysaccharide, was isolated from longan pulp.

  • The structural characteristics of LPIIa were elucidated by methylation, FT-IR, NMR, and GC–MS.

  • LPIIa had anti-inflammatory activity in LPS-treated RAW264.7 cells.

  • LPIIa protected the integrity of the intestinal barrier in vitro.

Abstract

In this study, LPIIa, a purified polysaccharide from longan pulp, was isolated. Its anti-inflammatory activity and intestinal barrier protection were investigated with LPS-treated co-culture model of Caco-2 cells and RAW 264.7 macrophages. The average molecular weight LPIIa was 159.3 kDa. Its detailed structure was shown below. The backbone of LPIIa was composed of (1→3,4)-linked-α-Rhap, (1→4)-linked-β-Galp, (1→6)-linked-β-Galp, and (1→3,6)-linked-β-Galp, with branches at the O-4 of Rha and O-3 of Gal, consisting of side chains of α-Araf, β-Galp, and α-Glcp. In LPS-induced RAW 264.7 macrophages, LPIIa suppressed the production of inflammatory mediators, including TNF-α, IL-6, NO, and PGE2, and inhibited iNOS and COX-2 gene expression. In addition, LPIIa attenuated intestinal tight-junctional channel protein Claudin-2 expression and increased tight-junctional barrier protein ZO-1 expression in Caco-2 cells. Knowing the structural features and activities of longan polysaccharide gives insights into longan polysaccharide application as an anti-inflammatory agent or adjuvant in curing the intestinal inflammation.

Introduction

Inflammatory bowel disease (IBD) is a chromic intestinal inflammatory disease, which severely compromises the quality of the patients’ daily life and is affecting massive population around the world (Staudacher, Irving, Lomer, & Whelan, 2014). The intestinal barrier destruction is the fundamental in IBD process (Gao et al., 2018; Gong, Li, & Li, 2016; Khan & Ghia, 2010). The intact intestinal epithelium is an important physical intestinal barrier by separating intestinal luminal antigens and immune cells to maintain intestinal homeostasis. Destruction of intestinal epithelial barrier increased the risk of luminal antigens flowing into the immune system, leading to inappropriate sustained immune responses (Arijs et al., 2011), which in turn results in continuous inflammatory responses (Gao et al., 2018; Gong et al., 2016; Khan & Ghia, 2010; Nagao-Kitamoto et al., 2016). In active IBD process, pro-inflammatory cytokines increased, including tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-6, and IL-8, which play an important role in activating and facilitating the intestinal mucosal inflammation (Bergmann et al., 2013; Putt, Pei, White, & Bolling, 2017). Meanwhile, inflammatory mediators oxide synthase (NO) and prostaglandin E2 (PGE2), which are produced by inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), respectively, were enhanced at the apical side of epithelial cells, indicating that they are involved in mediating the inflammatory process of intestinal tissue injury (Wang, Li, Yang, & Yao, 2013; Sun, Shi, Zheng, Nie, & Xu, 2019). Therefore, inhibiting inflammatory response is one of the effective ways in IBD therapy.

Natural products with low side effects and possible therapeutic effects on IBD attracted wide attentions. Studies have revealed that supplementation with natural polysaccharides is considered as an alternative or complementary treatment for IBD (Canani et al., 2011; Sun et al., 2019; Wang et al., 2013; Zuo et al., 2015). Longan (Dimocarpus longan Lour.) is an important edible-medicinal fruit with pleasant taste and high nutritional value. Polysaccharide is one of the main bioactive ingredients of longan pulp. It has potent anti-inflammatory (Kunworarath, Rangkadilok, Suriyo, Thiantanawat, & Satayavivad, 2016), immunomodulatory (Rong et al., 2019; Yi et al., 2012), and intestinal-flora-regulatory effects (Zhang et al., 2017). Previously, we found that crude longan pulp polysaccharide (LP) protected intestinal barrier by increasing the expression of tight junction proteins in intestinal epithelia in chemotherapy mice (Bai et al., 2019). The structure of polysaccharides is correlated with their activities (Shen, Jiang, Li, Zheng, & Zhu, 2017). However, the detailed structure of LP is still unclear. Therefore, this study elucidated the detailed structure of LPIIa, a purified active polysaccharide from LP. The anti-inflammatory activity and intestinal barrier protection of LPIIa was evaluated by the LPS-treated co-culture model of Caco-2 enterocyte-like cells with RAW 264.7 macrophages, which simulates the intestinal inflammatory process and mimics the acute phase of IBD (Olejnik et al., 2016).

Section snippets

Materials and reagents

Longan (cv. Chu-liang) fruit was provided by the Pomology Research Institute of Guangdong Academy of Agricultural Sciences (Guangzhou, China). The human colon cancer cell line Caco-2 and murine macrophage cell line RAW 264.7 were obtained from the Type Culture Collection of the Chinese Academy of Sciences (Shanghai, China). DEAE-Sepharose Fast Flow column and HiPrep Sephacryl S-300 HR column were purchased from GE Healthcare (Uppsala, Sweden). Monosaccharide standards (rhamnose, arabinose,

Basic chemical composition of LP-IIa

The carbohydrate and uronic acid contents of LP-IIa were 69.11 ± 1.79 % and 10.32 ± 0.67 %, respectively. Its protein content was 0.48 ± 0.20 %. It is indicated that LP-IIa was mainly comprised of neutral sugar and sort of acid sugar. The neutral monosaccharide compositions of LP-IIa were rhamnose, ribose, arabinose, xylose, glucose and galactose in a molar ratio of 1.05:1:22.88:1.01:2.59:34.58 (Fig. 1B). It represents that arabinose and galactose were the main monosaccharide compositions of

Conclusion

In this study, a bioactive longan pulp polysaccharide named LPIIa was isolated and its detailed structure was elucidated. Its average molecular weight was 159.3 kDa. The backbone of LPIIa was composed of (1→3,4)-linked-α-Rhap, (1→4)-linked-β-Galp, (1→6)-linked-β-Galp, and (1→3,6)-linked-β-Galp, with branches at the O-4 of Rha and O-3 of Gal, consisting of side chains of α-Araf, β-Galp, and α-Glcp. Meanwhile, LPIIa exhibited the anti-inflammation via decreasing the pro-inflammatory mediators and

Declaration of Competing Interest

There are no conflicts to declare.

Acknowledgements

This work was supported by the National Key Research Project of China (2017YFC1601002), Guangdong Provincial Science and Technology Project (2018A050506050), Guangdong special support program (2019BT02N112), Guangzhou Science and Technology Plan Project (202002030315), and the Special fund for scientific innovation strategy-construction of high level Academy of Agriculture Science (201602TD).

References (54)

  • X. Ji et al.

    An acidic polysaccharide from Ziziphus Jujuba cv. Muzao: Purification and structural characterization

    Food Chemistry

    (2019)
  • G.D. Kang et al.

    Poncirin and its metabolite ponciretin attenuate colitis in mice by inhibiting LPS binding on TLR4 of macrophages and correcting Th17/Treg imbalance

    Journal of Ethnopharmacology

    (2016)
  • N. Kunworarath et al.

    Longan (Dimocarpus longan Lour.) inhibits lipopolysaccharide-stimulated nitric oxide production in macrophages by suppressing NF-kappaB and AP-1 signaling pathways

    Journal of Ethnopharmacology

    (2016)
  • J.S. Lee et al.

    Purification, characterization and immunomodulating activity of a pectic polysaccharide isolated from Korean mulberry fruit Oddi (Morus alba L.)

    International Immunopharmacology

    (2013)
  • N. Li et al.

    Structural characterization and anticoagulant activity of a sulfated polysaccharide from the green alga Codium divaricatum

    Carbohydrate Polymers

    (2015)
  • W. Liu et al.

    Structure, chain conformation, and immunomodulatory activity of the polysaccharide purified from Bacillus Calmette Guerin formulation

    Carbohydrate Polymers

    (2016)
  • Z. Mitic et al.

    Synthesis, spectroscopic and structural characterization of Co(II)-pullulan complexes by UV-Vis, ATR-FTIR, MALDI-TOF/TOF MS and XRD

    Carbohydrate Polymers

    (2018)
  • Ž. Mitić et al.

    FTIR spectroscopic characterization of Cu(II) coordination compounds with exopolysaccharide pullulan and its derivatives

    Journal of Molecular Structure

    (2009)
  • Z. Mitic et al.

    Instrumental methods and techniques for structural and physicochemical characterization of biomaterials and bone tissue: A review

    Materials Science & Engineering C, Materials for Biological Applications

    (2017)
  • H. Nagao-Kitamoto et al.

    Functional characterization of inflammatory bowel disease-associated gut dysbiosis in gnotobiotic mice

    Cellular and Molecular Gastroenterology and Hepatology

    (2016)
  • C. Nie et al.

    Purification, characterization and immunomodulatory activity of polysaccharides from stem lettuce

    Carbohydrate Polymers

    (2018)
  • Y. Ren et al.

    Polysaccharide of Hericium erinaceus attenuates colitis in C57BL/6 mice via regulation of oxidative stress, inflammation-related signaling pathways and modulating the composition of the gut microbiota

    The Journal of Nutritional Biochemistry

    (2018)
  • Y. Rong et al.

    Structural characterization of an active polysaccharide of longan and evaluation of immunological activity

    Carbohydrate Polymers

    (2019)
  • C.-Y. Shen et al.

    Structural characterization and immunomodulatory activity of novel polysaccharides from Citrus aurantium Linn. variant amara Engl

    Journal of Functional Foods

    (2017)
  • Y. Sun et al.

    Inhibition of dextran sodium sulfate-induced colitis in mice by baker’s yeast polysaccharides

    Carbohydrate Polymers

    (2019)
  • X. Wang et al.

    Astragalus polysaccharide reduces inflammatory response by decreasing permeability of LPS-infected Caco2 cells

    International Journal of Biological Macromolecules

    (2013)
  • X. Wang et al.

    Extraction, isolation and structural characterization of a novel polysaccharide from Cyclocarya paliurus

    International Journal of Biological Macromolecules

    (2019)
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