Journal of Analytical & Bioanalytical Techniques
Open Access

Research Article

Quantification of Sugar Epimers in Polygalactomannans by ESI-MS/MS

Erika Ponzini¹, Greta Borgonovo¹, Luca Merlini², Yves M Galante², Carlo Santambrogio^1* and Rita Grandori^1*

¹Department of Biotechnology and Biosciences, University of Milano-Bicocca, Piazza della Scienza 2, 20126, Milan, Italy

²Istituto di Chimica del Riconoscimento Molecolare, CNR, Via Mario Bianco 9, 20131, Milan, Italy

*Corresponding Author:

Carlo Santambrogio
Department of Biotechnology and Biosciences
University of Milano-Bicocca Piazza della Scienza 2
20126 Milan, Italy
Tel: 39-02-64483363
E-mail: carlo.santambrogio@unimib.it

 

Rita Grandori
Department of Biotechnology and Biosciences
University of Milano-Bicocca
Piazza della Scienza 2, 20126 Milan, Italy
Tel: 39-02-64483363
E-mail: rita.grandori@unimib.it

Received date: September 03, 2015; Accepted date: September 25, 2015; Published date: October 02, 2015

Citation: Ponzini E, Borgonovo G, Merlini L, Galante YM, Santambrogio C (2015) Quantification of Sugar Epimers in Polygalactomannans by ESI-MS/MS. J Anal Bioanal Tech 6:281. doi:10.4172/2155-9872.1000281

Copyright: © 2015 Ponzini E, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Polygalactomannans (PGMs) represent an important family of polysaccharides. They are obtained from the endosperm of leguminous plant seeds and are employed in a growing number of industrial applications as thickening agents and rheology modifiers. Each PGM has a typical mannose/galactose (M/G) ratio (from ~1 to ~5), which determines its solubility, viscosity and other physico-chemical properties. Complex polysaccharides are commonly characterized by proton nuclear magnetic resonance (1H-NMR), whereas mass spectrometry (MS) has not yet seen wide application. In this work, a new quantification method for sugar epimers in PGMs is presented, based on the characteristic fragmentation patterns of mannose and galactose in tandem MS (MS/MS) analyses. Standard galactose and mannose have been analyzed and fragmented in negative-ion mode on a hybrid quadrupole/time-of-flight (qTOF) mass spectrometer equipped with a nano electrospray ionization (ESI) source. The MS/MS spectra indicate accumulation of the same fragments for the two monosaccharides, but significant and reproducible differences in the relative intensities of the product ions. Known mixtures of mannose and galactose have been analyzed by the same procedure to test the applicability of the method for quantification purposes. The resulting peak intensities over the entire MS/MS spectrum can be deconvoluted as a linear combination of the signals from pure mannose and galactose standards, obtaining reliable and reproducible quantification of the epimers. The method has been applied to the characterization of hydrolysis products of PGMs from different species of leguminous plants, such as guar (Cyamopsis tetragonolobus), sesbania (Sesbania bispinosa) and tara (Caesalpinia spinosa), in order to assess specific susceptibility to hydrolysis conditions.

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