Structural characterisation of a heteropolysaccharide by NMR spectra LiBin Ye a,b , JingSong Zhang a, * , Yan Yang a , Shuai Zhou a , YanFang Liu a , QingJui Tang a , XiuJu Du a,b , Hui Chen a , YingJie Pan c a Institute of Edible Fungi, Shanghai Academy of Agricultural Sciences, Shanghai 201106, PR China b College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, PR China c College of Food Science & Technology, Shanghai Ocean University, Shanghai 200090, PR China article info Article history: Received 23 March 2008 Received in revised form 28 April 2008 Accepted 8 July 2008 Keywords: Ganoderma lucidum Polysaccharide Structural elucidation NMR abstract An undocumented water-soluble polysaccharide, LZ-C-1, was isolated from the fruiting bodies of the fungus, Ganoderma lucidum. The polysaccharide had a molecular weight of 7  10 3 Da, and was mainly composed of L-Fuc, D-Glc and D-Gal. LZ-C-1 had a sugar content of 96.4% as measured using the phe- nol–sulphuric acid method. As a precondition to understand the bioactivity, structural features of LZ-C-1 were investigated by a combination of total hydrolysis, methylation analysis, FT-IR and NMR studies. The results indicated that LZ-C-1 had a backbone of 1,6-disubstituted-a-galactopyranosyl, 1,2,6-trisubsti- tuted-a-galactopyranosyl, 1,3-disubstituted-b-glucopyranosyl and 1,4,6-trisubstituted-b-glucopyranosyl residues. The branches were mainly composed of 1-substituted-b-glucopyranosyl and 1-substituted-a- fucopyranosyl residues. Crown Copyright Ó 2008 Published by Elsevier Ltd. All rights reserved. 1. Introduction The properties and functions of glycoconjugates and polysac- charides cover a wide range, from energy storage and structural blocks to the definition of the specificity of intercellular interac- tions in many immunological responses. Since the first applications of NMR techniques in structural analysis of polysaccharides from edible mushroom (Kemmelmeier & Zhang, 1981), the NMR spec- trum has become a powerful tool used to elucidate the structures of polysaccharides from mushrooms. Ganoderma lucidum is a kind of fungi belonging to Ganodermataceae. As a traditional Chinese medicine, it has been used for the prevention and treatment of dis- eases for several thousand years (Lin, 2001). As an extract from G. lucidum, polysaccharides/glycoconjugates have showed strongly bioactive properties towards anti-tumor (Maruyama, Yamazaki, Murofushi, Konda, & Ikekawa, 1989; Zhang & Lin, 1999), inhibiting spontaneous and Fas-mediated apoptosis in human neutrophilis (Hsu, Lee, & Lin, 2002), anti-angiogenic activity (Cao & Lin, 2004) and immuno-modulating activities (Lin et al., 2006), etc. The deter- mination of the structure of polysaccharides was necessary in or- der to establish a fundamental guide for assessing the bioactivity and pharmacological mechanism in vivo/in vitro. In previous work, the polysaccharide moiety structure of a glycopeptides (Ye et al., 2008) has been reported by our group. As a prelude to further investigations of structure–activity relationships, another polysac- charide was isolated from the fruiting bodies of G. lucidum strain 119, and the chemical structure of this polysaccharide was investi- gated herein. 2. Experimental 2.1. Materials The fruiting bodies of G. lucidum were collected by Dr. Jingson Zhang from Chongming district of Shanghai, People’s Republic of China, and were authenticated by Prof. Taihui Li, Guangdong Pro- vincial Key Laboratory of Microbial Culture Collection and Applica- tion, People’s Republic of China. At the same time, a voucher specimen had been preserved in the Institute of Edible Fungi, Shanghai Academy of Agricultural Sciences (Accession No. LZ- 2004-0119). BCA TM protein assay reagent kit was purchased from Pierce chemical company (Rockford, USA). The standard monosac- charides were from Sigma–Aldrich Company and Alamar Blue TM re- agent was bought from Biosoure International Company. A Millipore Milli-Q Plus (Bedford, MA, USA) was used to generate deionized (18.2 mX/cm) water in-house. 2.2. Instrumentation The ÄKTAprime plus and ÄKTA explorer equipped with a RID- 10A refractive index detector (SHIMADZU) were bought from Amer- sham Biosciences. The Waters HPLC system consisted of a model 0308-8146/$ - see front matter Crown Copyright Ó 2008 Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2008.07.017 * Corresponding author. E-mail address: zhangjs88888@163.com (J. Zhang). Food Chemistry 112 (2009) 962–966 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem