An amendment to the fine structure of galactoxyloglucan from Tamarind (Tamarindus indica L.) seed

A polysaccharide from tamarind seeds (TSP) was characterized in terms of backbone and side chain structural features, as well as conformational property using methylation and GC-MS analysis, 2D NMR, MALDI-TOF MS, and high performance size exclusion chromatography ( HPSEC). Results showed that TSP was a galactoxyloglucan (GXG) consisting of glucose, xylose, and galactose in a molar ratio of 3.1: 1.7: 1.0. The Mw was determined to be 524.0 k Da with radius of gyration (12g) of 55.6 nm. The chemical structure was confirmed as a dassical beta-(1- 4)-glucan with short side chains of T-beta-Galp-(1 2)-alpha-Xylp-( 1 -> and T-alpha-Xylp-(1 -> attached to 0-6 position of glucose. MALDI-TOF MS analysis indicated that TSP mainly composed of nonasaccharide (XLLG) and octasaccharide (XLXG or XXLG) blocks in periodic or interrupted sequence in a ratio of 3: 2, occasionally interrupted by heptasaccharide (XXXG), hexasaccharide (XLG or XXGG), or even hendesaccharide blocks. Conformational study indicated that TSP was in a random-coil shape with relative extended stiff chain in aqueous solution. This study provided more evidences to make an amendment to the fine structure of tamarind GXG. (C) 2020 Elsevier B.V. All rights reserved.