Structure elucidation of a pectin from Dendrobium nobile Lindl. and its immunological activity

Jun-Hui Wang,Ya-Di Zhang,Jian-Ping Luo

doi:10.1080/13102818.2018.1445031

Jun-Hui Wang, Ya-Di Zhang + Show 1 more

Open Access

https://doi.org/10.1080/13102818.2018.1445031

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Abstract

ABSTRACTIn this study, an RG-I pectin DNP-W6 was isolated from the stems of Dendrobium nobile Lindl. (Orchidaceae). It contained mannose, glucose, galactose, galacturonic acid and rhamnose in a molar ratio of 0.6: 1.0: 1.5: 1.1: 1.0. Its structural features were revealed by chemical, physical and spectral analysis. The results suggested that DNP-W6 possessed a backbone of a disaccharide of →4)-α-GalAp-(1→2)-α-Rhap-(1→, with approximate 50% substitution at O-4 of the rhamnopyranosyl residues. The side chains were neutral chains including galactosyl, mannosyl and glucosyl chains. The acetyl content was estimated to be 8.9%. The immunological results indicated that DNP-W6 and its derivatives exhibited different immunological activities in vitro, showing that the side chains and acetyl groups had an important effect on the expression of immunological activities.

Highlights

Pectic polysaccharides are a complex family of polysaccharides which occur naturally as structural elements in the primary cell walls and intracellular regions of higher plants [1,2]
An RG-I pectin DNP-W6 was isolated from the stems of Dendrobium nobile Lindl. (Orchidaceae)
After fractionation on DEAE-cellulose chromatography, a fraction was obtained from 0.5 mol/L NaCl eluate. It was further purified by Sephacryl S-200 gel filtration chromatography and gave a homogeneous polysaccharide DNP-W6 confirmed by high performance gel permeation chromatography (HPGPC) (Figure 1)

Summary

Introduction

Pectic polysaccharides are a complex family of polysaccharides which occur naturally as structural elements in the primary cell walls and intracellular regions of higher plants [1,2]. RG-I contains a backbone of the repeating disaccharide [!4)-a-GalAp-(1!2)-a-Rhap-(1!] with substitution at O-4 of the Rhap residues [4]. RG-II is not structurally related to RG-I, since its backbone consists of alternating sequences of Rha and GalA rather than the repeating disaccharide [!4)-a-GalAp-(1!2)-a-Rhap(1!] [5]. The research on bioactivity and structure–activity relationship of pectin indicates that the pectic polysaccharides exhibit a variety of biological activities, such as anti-complementary, anti-tumor and immunological activities [6,7,8]. (Chinese name ‘Jin-Chai-ShiHu’) is a well-known edible and medicinal plant with wide distribution in the southwest and south of China. It is recorded in Chinese Pharmacopoeia [15]. We elucidate the structural features and pharmacological activities of DNP-W6, as well as its structure–activity relationship

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