Elsevier

Carbohydrate Polymers

Volume 196, 15 September 2018, Pages 246-253
Carbohydrate Polymers

Structural analysis and antioxidant activities of neutral polysaccharide isolated from Epimedium koreanum Nakai

https://doi.org/10.1016/j.carbpol.2018.05.037Get rights and content

Highlights

  • A neutral polysaccharide was isolated from Epimedium koreanum Nakai.

  • FPN-1 was a heteropolysaccharide containing over 60% of glucose.

  • The backbone of EFPN-1 was composed of 4- and 4, 6-α-D-Glcp.

  • EFPN-1 was a branched polysaccharide with a degree of branching of 40.40%.

  • EFPN-1 possessed better antioxidant activity in vitro.

Abstract

The structure and antioxidant activity of a neutral polysaccharide (named as EFPN-1) from Epimedium koreanum Nakai were studied. Based on the results from high performance gel permeation chromatography, methylation GC–MS and 1D/2D nuclear magnetic resonance spectroscopy, EFPN-1 was a branched polysaccharide with a molecular weight of 21.9 kD and containing over 60% of glucose. Its backbone was composed of (1 → 4)-β-d-Glcp and (1 → 3)-β-d-Galp, branched partially at O-6 of both residues, with a degree of branching of 40.4% and terminated mainly with Ara and Gal, as well as trace amount of Gal. Antioxidant tests showed that EFPN-1 exhibited a strong capacity on DPPH and hydroxyl radical scavenging, ferrous ion chelation and reducing antioxidant powder. EFPN-1 has potential to be developed as a natural antioxidant.

Introduction

Epimedium folium is one of the famous traditional Chinese herbs. China is the centre of modern geographical distribution of Epimedium. Until now, a total of 52 species distributed in China have been found in the genus of Epimedium L. (Stearn, 2002). In the past decade, the chemical compounds and pharmacological activities of Epimedium. L has been extensively studied. The whole plant can be used for medicinal purposes and have been demonstrated to be beneficial to supplement kidney and strengthen yang, strengthen the bones and muscles, and show antirheumatic properities (Jiang, Song, & Jia, 2015). Moreover, over 270 chemical constituents have been distinguished (Wu, Lien, & Lien, 2003), including flavonoids, alkaloids, lignans and terpenic compounds (Jiang et al., 2015).

Polysaccharides, which are active ingredients in traditional Chinese medicine, have attracted considerable attention because of their antioxidant, antimicrobial, immunoregulatory and anti-inflammatory activities (Liu, Willfor, & Xu, 2015). Polysaccharides isolated from different species of plant, algae or fungi possess different biological functions and structural properties. Pan et al. (2014) found that the polysaccharides isolated from four different Dendrobium species possess different hypoglycemic and antioxidant activities. Meanwhile, Fernández, Arata, and Ciancia (2014) also found that the difference in origin will affect the structural characteristics of polysaccharides, even if they belong to the same species. Their findings suggest that the structural units of sulphated galactans in Codium fragile collected from Argentina and Japan were different. Recently, some polysaccharides of Epimedium have been reported. For example, some researchers have studied the neutral and acid polysaccharides from E. acuminatum Franch, which belongs to the same of genus as E. koreanum Nakai (Cheng et al., 2013; Wu et al., 2016; Xu, Zhang, & Wang, 2016). Xu et al. (2016) found that both neutral and acid polysaccharides purified from E. acuminatum Franch contained xylose as the major sugar, with the content more than 50% (Xu et al., 2016). Cheng et al. (2013) and Wu et al. (2016) also demonstrated that the E. acuminatum Franch polysaccharides might be used as potential natural antioxidants and immunostimulants. However, the structures of these polysaccharides have not been explored.

E. koreanum Nakai is one of the main sources of Epimedium, which only grows in Northeast China (Ying, 2001). Research on E. koreanum Nakai has mainly focused on the flavonoids (Hwang, Yang, Yim, & Ma, 2017). To date, few reports are available on the polysaccharides from E. koreanum Nakai. Therefore, in this paper, we extracted and purified the polysaccharides of E. koreanum Nakai and determined the structure and antioxidant activity of its neutral polysaccharides.

Section snippets

Plant material and reagents

E. koreanum Nakai used in this work was collected from Dongfeng Country, Songyuan City, Jilin Province, China in June, 2009. The taxonomical characteristics of this plant were identified by Professor Lili Weng, and the voucher specimen (20160002) was kept at the College of Pharmaceutical Sciences, Changchun University of Chinese Medicine.

Monosaccharide standards, galacturonic acid (GalA) and dextran standards (0.1, 0.5, 12.6, 20.0, and 50.0 kDa) were purchased from Sigma chemical Co (USA). All

Purification and characterization of EFPN-1

The neutral polysaccharide EFPN of E. koreanum Nakai was obtained by hot water extraction followed by ion-exchange and gel permeation chromatography, and exhibited a single peak (designated as EFPN-1) accounting for 76.4% of the total sugar eluted. As seen in Fig. 1, EFPN-1 displayed a signal and symmetrical peak with a low polydispersity index of 1.1, thereby indicating that the EFPN-1 was a homogeneous polysaccharide. Basing on its retention time on the HPGPC system, the Mw of EFPN-1 was

Conclusion

In this work, the neutral polysaccharide EFPN-1 was prepared by water extraction, ion-chromatography and gel-permeation chromatography. The polysaccharide consisted of Rha, Glc, Gal and Ara in the molar ratio of 1.47: 6.5: 1.90: 0.76. EFPN-1 mainly consisted of 4-Glcp and 3, 6-Galp residues and a small amount of 3-Rhap, 3-Galp and 4,6-Glcp, and was terminated mainly with t-Araf and t-Glcp. EFPN-1 had potent antioxidant activities, including elimination of DPPH and hydroxyl radical, as well as

Acknowledgements

We are grateful for the National Foundation of China [grant number 31700703], the Baiqing Plan Project of Changchun University of Chinese Medicine, the financial support of Jilin Provincial Administration of traditional Chinese Medicine [grant number 2017179], and the Science and Technology Development Plan Project of Jilin Province [grant number 20170204010YY].

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    These authors contributed equally to this paper.

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