Carbohydrate Polymers 99 (2014) 800–807 Contents lists available at ScienceDirect Carbohydrate Polymers jo u r n al homep age: www.elsevier.com/locate/carbpol Arabinoxylan from finger millet (Eleusine coracana, v. Indaf 15) bran: Purification and characterization M.R. Savitha Prashanth, G. Muralikrishna ∗ Department of Biochemistry and Nutrition, CSIR-Central Food Technological Research Institute, Mysore 570 020, Karnataka, India a r t i c l e i n f o Article history: Received 29 April 2013 Received in revised form 15 August 2013 Accepted 25 August 2013 Available online xxx Keywords: Finger millet Arabinoxylan Purification Structure NMR FTIR a b s t r a c t Water unextractable portion from finger millet bran was sequentially extracted with saturated barium hydroxide (BE) and 1 M potassium hydroxide (KE) solutions. They consisted preponderantly of arabi- nose and xylose in different ratios. Ferulic, caffeic, coumaric and vanillic acids were identified as major bound phenolic acids. BE and KE were purified on DEAE-cellulose column by eluting successively with different eluants. The major fractions (0.1 M ammonium carbonate) were resolved into one (BE) and two subfractions (KE1 and KE2) respectively on Sephacryl S-400 gel filtration chromatography and their homogeneity was ascertained by gel filtration, cellulose acetate membrane electrophoresis and capillary electrophoresis. The average molecular weight of BE, KE1 and KE2 were found to be 430, 1028 and 40 kDa respectively. The structural elucidation of the purified polysaccharides by 1 H and 13 C NMR analysis indi- cated the backbone to be 1,4--d-linked xylan with substitution mainly at O-2 or O-3 and/or both by -l-arabinose residues. © 2013 Published by Elsevier Ltd. 1. Introduction Finger millet (Eleusine coracana), one of the widely used millets in southern part of India has many nutritional benefits because of its high content of calcium (0.34%) and dietary fiber (18%) which are higher compared to other cereals such as wheat, maize, rice and barley (Kamat & Belavady, 1980; Ravindran, 1991). Finger mil- let contains less protein and fat but, it contains highest amount of methionine, among cereal grains. It is consumed as whole flour, thereby retaining the fiber, phenolics, minerals and vitamins present in the outer layer of the grain. Hence, present day research is focused in identifying newer or natural sources of nutraceuticals and nutritional materials having desirable functional properties. Dietary fiber is classified into broad category, which includes con- stituents such as cellulose, pectin, arabinoxylan, lignin, ˇ-glucan, etc. (DeVries, 2004; Slavin, 2008). Among the dietary fiber components arabinoxylan (AX), has been identified in all major cereal grains such as wheat, rye, bar- ley, oat, rice, sorghum bajra and ragi and also in some other plants such as psyllium peels, pongal grass, bamboo shoots and rye grass (Fischer et al., 2004; Izydorczyk & Biliaderis, 1995). They are also described as pentosans and are vital in cell wall forma- tion. Additionally, they are important in determining the end use ∗ Corresponding author. Tel.: +91 821 2514876; fax: +91 821 2517233. E-mail addresses: krishnagm2002@yahoo.com, gmk@cftri.res.in (G. Muralikrishna). quality of cereal-based food products (Finnie, Bettge, & Morris, 2006; Hartmann, Michael, & Peter, 2005; Revanappa, Nandini, & Salimath, 2010). They are of growing importance because of their health-beneficial effects in alleviating disease symptoms such as colon cancer, atherosclerosis, and diabetes (Biliaderis, Izydorczyk, & Rattan, 1995; Lu, Walker, Muir, & O’Dea, 2004). Being potent natu- ral immunomodulators and prebiotics, they are also considered as functional food ingredients (Charalampopoulos, Wang, Pandiella, & Webb, 2002). Arabinoxylans are composed of a main chain of (1 → 4)-linked -d-xylopyranosyl residues occasionally with var- ious degrees of substitution at O-2 or O-3 or at both O-2 and O-3 by arabinose and sometimes with uronic acid residue. Usually cinnamic acid derivatives such as ferulic and coumaric acids are substituted at O-5 of arabinose residues (Fincher & Stone, 1986). The structural features and molecular weight of polysaccharides are of fundamental importance since they influence certain phys- icochemical and functional properties of polymers (Izydorczyk, 2005). Hence the understanding of the structure require a high- purity arabinoxylan preparation without any contamination from other associated cell–wall components such as contaminating starch, (1 → 3/1 → 4)--d-glucans, cellulose, lignin and associated proteins. Most of the arabinoxylans are water unextractable and can only be extracted with alkali. An efficient method that facil- itates the fractionation and characterization of cereal AX was introduced in early nineties (Gruppen, Hamer, & Voragen, 1992) which involves saturated barium hydroxide as well as potassium hydroxide solutions has become the method of choice for extrac- tion of water unextractable AX from wheat, rye, barley and corn 0144-8617/$ – see front matter © 2013 Published by Elsevier Ltd. http://dx.doi.org/10.1016/j.carbpol.2013.08.079