Study on Dendrobium officinale O-acetyl-glucomannan (Dendronan®): Part V. Fractionation and structural heterogeneity of different fractions
Introduction
Considering the medicinal and commercial interest in the Dendrobium officinale herb in China, it is meaningful to obtain highly purified polysaccharide samples from D. officinale herbal materials and reveal the structure–conformation relationship of the Dendrobium polysaccharide samples, which are the prerequisites to understanding the mechanism of action of bioactive D. officinale polysaccharides (Xing et al., 2013). In many cases, fractionation of polysaccharide sample is necessary, because fractionation not only enhances the purity of polysaccharide sample but also generates a series of polysaccharide samples that share similar major structural characteristics but are slightly different in detailed structural features (Izydorczyk & Biliaderis, 1996). These samples can be valuable materials for study aimed at establishing the structure–conformation–bioactivity relationships.
In previous reports, anion exchange chromatographic (AEC) method and/or size exclusion chromatographic (SEC) method were used to fractionate Dendrobium polysaccharides (Hua et al., 2004, Wang et al., 2010, Zha et al., 2007). These chromatographic methods can result in polysaccharide fractions with very high purity, but are time-consuming, give low yields, and are not feasible for sample preparations for in vivo experiments using animal or human clinical trials, which require large amounts of polysaccharide samples. Purification and fractionation by gradient ethanol or ammonium sulfate precipitation method have gained increased importance (Guo et al., 2012, Izydorczyk and Biliaderis, 1996), because the precipitation method allows researchers to efficiently fractionate plant polysaccharide samples into many purified polysaccharide fractions based on the molecular weight and structural differences of these fractions. Previously, we successfully extracted a polysaccharide sample from D. officinale plant (Xing et al., 2014) and elucidated its major structure as 2,3-O-acetyl-glucomannan using 2D NMR technology (Xing et al., 2015). In the current study, we used ethanol precipitation method to fractionate the 2,3-O-acetyl-glucomannan to several fractions. We expected the fractionation could allow us to obtain a series of O-acetyl glucomannan samples with high purity and variable detailed structural features. The objectives of the current study were to investigate the Man/Glc ratio, the degree of substitution of O-acetyl group, and the distribution pattern of O-acetylated residues along the backbone chain of the obtained glucomannan fractions.
Section snippets
Fractionation of DOP
Purified D. officinale polysaccharide sample (DOP) was prepared according to our previous report (Xing et al., 2014). DOP (20 g) was dissolved in deionized water (2000 mL) to form a solution with polysaccharide concentration of 1% (w/w). Pure ethanol was then added slowly to the solution at room temperature with vigorous stirring to achieve a 20% (w/w) ethanol concentration in the mixture. The mixture was kept at 4°C for 6 h and then centrifuged at 10,000g and 4°C for 20 min. The residue produced
Yield, chemical analysis, HPSEC analysis, HPAEC analysis, and FTIR analysis
Results showed that F0-20 was rich in protein and had low yield, while the other four fractions contained very low level of proteins and had relatively high yields (Table 1). Therefore, future experiments were mainly focused on the four major fractions. As ethanol concentration increased the precipitated fractions had lower molecular weight, lower intrinsic viscosity, and higher polydispersity (Table 2). In Fig. 1, F20-30, F30-40, and F40-50 showed very sharp peaks. Compared with other
Conclusions
Gradient ethanol precipitation was a useful method for the fractionation of 2,3-O-acetyl glucomannan. The four major resultant fractions F20-30, F30-40, F40-50, and F50S had high purity. F20-30 and F30-40 had low polydispersity, which was suitable for batch mode light scattering study. Fractions obtained in solution with higher ethanol concentration tended to have higher Man/Glc ratio, higher degree of substitution of O-acetyl group, lower molecular weight, and lower intrinsic viscosity. A
Acknowledgments
This study was financially supported by the International Science & Technology Cooperation Program of China (2013DFA32710), which is gratefully acknowledged. This project was also partially supported by a grant with University of Guelph, Guelph, Ontario, Canada. The authors would like to thank Ms. Fang Tian, president of Jin-Jiu-Di Biotechnology Co. Ltd., Yunan, China, for providing the freeze-dried D. officinale stem samples.
References (10)
- et al.
Structural characterization of a low-molecular-weight heteropolysaccharide (glucomannan) isolated from Artemisia sphaerocephala Krasch
Carbohydrate Research
(2012) - et al.
Structural characterization of a 2-O-acetylglucomannan from Dendrobium officinale stem
Carbohydrate Research
(2004) - et al.
Gradient ammonium sulphate fractionation of galactomannans
Food Hydrocolloids
(1996) - et al.
Comparison of antitumor activities of different polysaccharide fractions from the stems of Dendrobium nobile Lindl
Carbohydrate Polymers
(2010) - et al.
Study of Dendrobium officinale O-acetyl-glucomannan (Dendronan®): Part I. Extraction, purification, and structural characterization
Bioactive Carbohydrates and Dietary Fibre
(2014)
Cited by (19)
Comprehensive evaluation of the prebiotic properties of Dendrobium officinale polysaccharides, β-glucan, and inulin during in vitro fermentation via multi-omics analysis
2023, International Journal of Biological MacromoleculesThe structures of two glucomannans from Bletilla formosana and their protective effect on inflammation via inhibiting NF-κB pathway
2022, Carbohydrate PolymersCitation Excerpt :Consequently, no acetyl groups are substituted at C-6 based on the 13C, DEPT135, and 2D NMR (Fig. S5B and S6D). The degrees of substitution of the O-acetyl groups at the C-2 and C-3 position were 5.99% and 7.65% for BFP60, 5.70% and 7.12% for BFP80 (Table S4), respectively, by the proton signal integration in the 1H NMR spectrum (Xing et al., 2015b). The reducing end β-d-Man residue (residue G) and α-d-Man residue (residue H) were identified according to the previous literature (Tenkanen, Makkonen, Perttula, Viikari, & Teleman, 1997; Xing et al., 2015a).
Isolation, structural properties, bioactivities of polysaccharides from Dendrobium officinale Kimura et. Migo: A review
2021, International Journal of Biological MacromoleculesCitation Excerpt :It is believed that the presence of large numbers of acetyl groups makes it complex and difficult to characterize the structures [17]. Among these polysaccharides, most of the compounds with bioactivity are O-acetylated glucomannan, in which the skeletons of the repeating units usually contain 1,3-, 1,4-, or 1,6-linked glycosyl residues [4,47,52]. So far, literature data present different structural characteristics results of D. officinale polysaccharides, including chain conformations, configuration, glycosidic linkages types, branching sites, and side chains.
Effect of the polysaccharides derived from Dendrobium officinale stems on human HT-29 colorectal cancer cells and a zebrafish model
2021, Food BioscienceCitation Excerpt :Dendrobium officinale has been used as a functional food and important medicine in China for more than a thousand years (Ng et al., 2012). Previous studies have shown a variety of bioactive substance in D. officinale, including polysaccharides (Tao et al., 2019; Xing et al., 2015), flavonoids (Zhou et al., 2018), alkaloids (Chen et al., 2019; Guo et al., 2013), and bibenzyl (Li et al., 2014). Furthermore, polysaccharides are one of the main active ingredients in D. officinale (Nie et al., 2018; Zhao et al., 2017).
Metabolism amelioration of Dendrobium officinale polysaccharide on type II diabetic rats
2020, Food HydrocolloidsCitation Excerpt :Especially, polysaccharide is one of the most important bioactive compounds of Dendrobium officinale, which was mainly consisted of mannose and glucose (in a molar ratio of 6.9:1) with a Mw (molecular weight) of 312 kDa (Xing et al., 2014). The polysaccharide is compose of →4)-Manp-(1→and →4)-Glcp-(1→ as the main chain and do not contain branches, acetyl groups are attached to the O-2 or O-3 positions on some mannosyl residues (Xing et al., 2015). Our previous studies found DOP possess a variety of health benefits including anti-oxidative stress injury (Huang et al., 2015), colonic health benefits (Zhang et al., 2016), and immunomodulatory activities (Cai et al., 2015), and all of these benefits are associated with alleviation of diabetes.