Preparation and structural characterization of a partially depolymerized beta-glucan obtained from Poria cocos sclerotium by ultrasonic treatment
Graphical abstract
Introduction
Polysaccharides from edible and medicinal fungi have attracted attention in the field of biopharmacological field due to their antitumor and immunomodulatory effects (Zeković et al., 2005, Zhang et al., 2007) including their direct tumor inhibition (Wasser, 2002). It has been reported that a polysaccharide extracted from Poria cocos significantly suppressed the proliferation of U937 and HL-60 cells (Chen & Chang, 2004). Polysaccharides isolated from Pleurotus tuber-regium, Pleurotus pulmonarius have been demonstrated to have potent cytotoxicity towards cancer cells (Xu et al., 2012, Zhang et al., 2004c). In vitro studies had indicated that incubation of mushroom polysaccharides with tumor cells could affect the intracellular signaling pathways that would lead to their inhibition of proliferation (Chen and Chang, 2004, Li et al., 2004, Lin et al., 2003).
Polysaccharides contain repetitive structural features which are polymers of monosaccharide residues joined to each other by glycosidic linkages and can be interconnected at several points to form a wide variety of branched or linear structures (Cheung, 2008). Numerous studies have been attempted to correlate biological activity and molecular weight of polysaccharides. Mizuno indicated that high molecular weight glucans appeared to be more effective than those of low molecular weight, especially (1-3)-β-glucans that ranged from 500 to 2000 kDa (Mizuno, 1996). Water solubility of polysaccharides is another factor that influences its bioactivity. Overall, the solubility of polysaccharides depends on their degree of polymerization and their physico-chemical properties (Zeković et al., 2005). It has been established that the immunomodulation of soluble and particulate beta-glucans is mediated by activation of CR3 and Dectin-1 receptors, respectively (Goodridge et al., 2011, Qi et al., 2011). However the insoluble nature of polysaccharides substantially limits their antitumor activity, as there have been studies suggesting that soluble polysaccharides exhibit more inhibitory effect than those insoluble ones (Chen et al., 2009, Chen et al., 2010). Chemical modifications of native polysaccharides by forming their carboxymethylated, hydroxylated, formylmethylated, aminoethylated and sulfated derivatives have been reported to enhance their aqueous solubility as well as improved antitumor activity (Wang et al., 2004a, Zhang et al., 2004a, Zhang et al., 2004b). Other than chemical methods, physical means such as ultrasonic, γ-ray, ultraviolet light and microwave treatments have been applied to modify the structure and properties of polysaccharides (Vodeničarová, Dřímalová, Hromádková, Malovíková, & Ebringerová, 2006). The main advantage of physical means over chemical methods is that no chemical reagents are required and hence removal of any excess chemicals is not necessary. Ultrasonic treatment is an effective method to partially depolymerize polysaccharides by glycosidic bond cleavage, the extent of which could be controlled by different power input and treatment time. A recent study on ultrasonic depolymerization of β-glucan from Cs-HK1, an exopolysaccharide (EPS) isolated from fermentation broth of a medicinal fungus Cordyceps sinensis, showed a significant increase in water solubility and antioxidant ability in the modified EPS (Chen, Siu, Cheung, & Wu, 2014).
The sclerotium of Poria cocos has been widely used in traditional Chinese medicine (Ríos, 2011). The main component of P. cocos sclerotium is a water-insoluble linear (1-3)-β-D-glucan, which had very modest antitumor activity (Ding et al., 1998, Wang et al., 2004a). Chemically modified polysaccharide derivatives from P. cocos sclerotium exhibited notably increased solubility and significant inhibitory effect towards S-180 tumor cells after phosphorylation (Chen et al., 2009). Till now, polysaccharide derivatives obtained from P. cocos sclerotium by ultrasonication have not been reported before. Therefore, in this study, water-insoluble polysaccharide extracted from the sclerotium of P. cocos by alkaline extraction was partially degraded using ultrasonic treatment to give a mushroom hydrocolloid. The chemical and physical properties of this mushroom hydrocolloid including water solubility, molecular weight, intrinsic viscosity and structural characteristics as well as its antitumor activity were determined. To our knowledge, this is the first report on modified β-glucan as a hydrocolloid prepared by ultrasonication from P. cocos sclerotium.
Section snippets
Alkaline extraction of polysaccharide
Sclerotium of P. cocos was originated from the Yunnan province, China. It was dried and pulverized into powders to pass through a screen with an aperture of 0.5 mm by using a cyclotech mill (Tecator, Hӧganäs, Sweden). Powders were defatted by ethyl acetate and then acetone, before subjected to a cold alkali extraction (1 M NaOH, room temperature, 16 h). The supernatant of the cold alkali-soluble fraction was first neutralized to pH 7.0 with 0.5 M HCl to yield precipitates which were washed for
Purification and chemical analysis of PCS0
In the present study, the untreated PCS sample (PCS0) obtained by membrane ultrafiltration (Mw cut-off 10 kDa) had significantly higher carbohydrate content (more than 20%) than the crude alkali mushroom extract (Fig. 1). Moreover, no protein and uronic acids were detected in PCS0 (data not shown), indicating it was only composed of neutral polysaccharide. The results indicated that the crude alkali mushroom extract could be purified by membrane ultrafiltration to give a reasonably pure
Discussion
P. cocos consists of three morphological forms, including mycelium, sclerotium and fruiting body, among which sclerotium has been studied extensively (Wang et al., 2004). In this project, an alkaline extraction was used since this PCS fraction would include the majority of polysaccharides (>84%) (Wang, Zhang, Ruan, et al., 2004) obtained from the sclerotium of P. cocos and this fraction has been demonstrated to exhibit anti-tumor or immunomodulatory activities after modification (Wang, Zhang,
Conclusion
A (1 → 3)-β-D-glucan (PCS) was purified by membrane ultrafiltration from a crude alkaline extract obtained from the sclerotium of P. cocos. Ultrasonic treatment was shown to be an effective means to partially depolymerize PCS, resulted in the reduction of Mw and viscosity as well as an increase in water solubility of the ultrasonic-treated PCS samples. Ultrasonication can also unfold the compact structure of PCS into an open chain conformation in aqueous medium. All the changes in the
Acknowledgments
This project was financially supported by the Research Committee of CUHK Directed Grant for Research (No. 2030435). The technical support provided by technicians from the School of Life Sciences and the Department of Physics of CUHK for FT-IR was gratefully acknowledged.
References (51)
- et al.
New method for quantitative determination of uronic acids
Analytical Biochemistry
(1973) - et al.
(1 → 3)-β-D-Glucans as biological response modifiers: a review of structure-functional activity relationships
Carbohydrate Polymers
(1995) - et al.
Antiproliferative and differentiating effects of polysaccharide fraction from fu-ling (Poria cocos) on human leukemic U937 and HL-60 cells
Food and Chemical Toxicology
(2004) - et al.
Structure and properties of a (1 → 3)-β-D-glucan from ultrasound-degraded exopolysaccharides of a medicinal fungus
Carbohydrate Polymers
(2014) - et al.
Cell wall structure of mushroom sclerotium (Pleurotus tuber regium): part 1. Fractionation and characterization of soluble cell wall polysaccharides
Food Hydrocolloids
(2014) - et al.
Chain conformation and anti-tumor activities of phosphorylated (1 → 3)-β-D-glucan from Poria cocos
Carbohydrate Polymers
(2009) - et al.
Cell wall structure of mushroom sclerotium (Pleurotus tuber-regium): Part 2. Fine structure of a novel alkali-soluble hyper-branched cell wall polysaccharide
Food Hydrocolloids
(2014) - et al.
Immunopotentiation and anti-tumor activity of carboxymethylated-sulfated β-(1 → 3)-d-glucan from Poria cocos
International Immunopharmacology
(2010) - et al.
Analysis of nitrate, nitrite, and [15N]nitrate in biological fluids
Analytical Biochemistry
(1982) - et al.
Protein determination using bicinchoninic acid in the presence of sulfhydryl reagents
Analytical Biochemistry
(1988)
Comparison of classical and ultrasound-assisted extraction of polysaccharides from Salvia officinalis L
Ultrasonics Sonochemistry
Rapid purification of polysaccharides using novel radial flow ion-exchange by response surface methodology from Ganoderma lucidum
Food and Bioproducts Processing
Protein-bound polysaccharide from Phellinus linteus induces G 2/M phase arrest and apoptosis in SW480 human colon cancer cells
Cancer Letters
Mechanochemical degradation kinetics of high-density polyethylene melt and its mechanism in the presence of ultrasonic irradiation
Ultrasonics Sonochemistry
Structure determination, apoptosis induction, and telomerase inhibition of CFP-2, a novel lichenin from Cladonia furcata
Biochimica et Biophysica Acta (BBA) – General Subjects
Rapid colorimetric assay for cellular growth and survival: application to proliferation and cytotoxicity assays
Journal of Immunological Methods
Determination of the maximum water solubility of eight native starches and the solubility of their acidic-methanol and ethanol modified analogues
Carbohydrate Research
Differential pathways regulating innate and adaptive anti-tumor immune responses by particulate and soluble yeast-derived β-glucans
Blood
Ultrasonic degradation of schizophyllan, an antitumor polysaccharide produced by Schizophyllum commune fries
Carbohydrate Research
Characterization and antioxidant activities of degraded polysaccharides from Poria cocos sclerotium
Carbohydrate Polymers
Ultrasonic-assisted extraction and antioxidant activity of polysaccharides recovered from white button mushroom (Agaricus bisporus)
Carbohydrate Polymers
Xyloglucan degradation using different radiation sources: a comparative study
Ultrasonics Sonochemistry
Ultrasonic treatment for improved solution properties of a high-molecular weight exopolysaccharide produced by a medicinal fungus
Bioresource Technology
Correlation of structure to antitumor activities of five derivatives of a β-glucan from Poria cocos sclerotium
Carbohydrate Research
Chemical components and molecular mass of six polysaccharides isolated from the sclerotium of Poria cocos
Carbohydrate Research
Cited by (45)
Comparative study on chain conformations, physicochemical and rheological properties of three acidic polysaccharides from Opuntia dillenii Haw. fruits
2024, International Journal of Biological MacromoleculesChemical structures, extraction and analysis technologies, and bioactivities of edible fungal polysaccharides from Poria cocos: An updated review
2024, International Journal of Biological MacromoleculesComposition, structural properties and immunomodulatory activity of several aqueous Pleurotus β-glucan-rich extracts
2023, International Journal of Biological MacromoleculesA curcumin oral delivery system based on sodium caseinate and carboxymethylpachymaran nanocomposites
2023, International Journal of Biological MacromoleculesInfluence of ultrasound assisted metal-free Fenton reaction on the structural characteristic and immunostimulatory activity of a β-D-glucan isolated from Dictyophora indusiata
2022, International Journal of Biological MacromoleculesCitation Excerpt :Both DP and DDP-1 exhibited the rigid rod chain conformation in water. Therefore, compare with DP, the significant increase of immunostimulatory effect of DDP-1 might be owing to its relatively low molar mass, which could cause the increase of its solubility that makes it easy to interact with macrophages [37]. However, the notable decrease of immunostimulatory effect of DDP-2 and DDP-3 might be due to the change in their chain conformation from rigid rod to random coil compared to DP [7,38,39].