1 e-Polymers 2011, no. 084 http://www.e-polymers.org ISSN 1618-7229 Fractional isolation and structural characterization of hemicellulosic polymers from Caragana sinica Ling-Ping Xiao, 1 Feng Xu, 1 , Run-Cang Sun 1 2* 1* Institute of Biomass Chemistry and Technology, Beijing Forestry University, Beijing, 100083, China; fax: +86-10-62336972; e-mail: rcsun3@bjfu.edu.cn 2 State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou, 510640, China; fax: +86-20-87111861; e-mail: xfx315@ bjfu.edu.cn (Received: 01 May, 2010; published: 17 August, 2011) Abstract: The cell wall material of Caragana sinica was fractionated by successive extractions with distilled water at 80 °C for 2 h, 70% ethanol, 70% ethanol containing 1% NaOH, 1 M KOH, 1 M NaOH, 3 M KOH, and 3 M NaOH at 75 °C for 3 h. The sequential treatments resulted in a total dissolution of 86.7% of the original hemicelluloses and 80.1% of the original lignin from dewaxed C. sinica. The current results showed that the four alkali-soluble hemicellulosic preparations, comprising almost 80% xylose of the total neutral sugars, were more linear and acidic, but lower molecular weights (  w , 28420- 55140 g/mol) than the other two organosolv-soluble hemicelluloses ( w , 57930-96470 g/mol). The 1 M KOH-soluble hemicellulosic fraction was characterized by sugar analysis and 1D, 2D NMR spectroscopy and was found to be composed of a linear (1→4)-ȕ-D-xylopyranosyl main chain with a 4-O- methylglucuronic acid substituting the C-2 position of approximately every eight xylose unit, which is typical of a hardwood acidic 4-O-methylglucuronoxylan (MGX). Introduction In recent years, due to growing environmental awareness, considerable attention has been given to the development and production of natural fibre reinforced polymer (both thermoset and thermoplastic) composites. The interest of using hemicelluloses as a renewable resource for new oligomeric and polymeric products is currently increasing. After cellulose, the next major polysaccharide resource is plant hemicelluloses. It consists of D-xylose, D-mannose, D-glucose, D-galactose, D-glucose, L-arabinose, 4-O-methyl-glucuronic, D-galacturonic and D-glucuronic acids. Sugars are linked together by ȕ-1,4- and occasionally ȕ-1,3- glycosidic bonds [1]. The most abundant hemicellulose constituent of hardwood is O-acetyl-(4-O-methylglucurono)-xylan. Previous studies showed that these hardwood xylans from a family of polysaccharides, which consist of a backbone of (1→4)-ȕ-D-xylopyranose residues, with, on average, one α-(1→β)-linked 4-O- methylglucuronic acid (MeGlcA) substituent per 10-20 such residues [2]. In plants, the xylopyranosyl can be substituted in C-2 and/or C-3 by short and flexible side chains [3]. Shortage of the natural energy sources and replacement of petroleum-based products, which is connected with the demand for solution of worldwide