13C-DOSY-TOSY NMR Correlation for In Situ Analysis of Structure, Size Distribution, and Dynamics of Prebiotic Oligosaccharides

Arabinoxylan oligosaccharides (AXOS) are a complex mixture of cereal derived, water-soluble prebiotics, obtained by enzymatic hydrolysis of arabinoxylan, a group of dietary fibers exerting numerous nutritional and health-beneficial effects. Such complex biomolecular mixtures are notoriously difficult to characterize without initial physical fractionation. Here we present the in situ analysis of AXOS using a variety of state-of-the-art sensitivity-enhanced C-13-DOSY methods, enabling virtual separation and identification of the components. Three dimensional correlation plots displaying C-13 diffusivity (DOSY: Diffusion Ordered SpectroscopY), relaxation parameters (TOSY: raTe of relaxation Ordered SpectrscopY), and chemical shift offer a unique way to elucidate the composition of mixtures. We have demonstrated this multifaceted C-13 probed correlation strategy in standard mixtures of aliphatic and aromatic compounds, before implementing it on AXOS. These 3D-DOSY-TOSY plots in combination with 2DNMR correlation experiments offer unprecedented clarity for assigning chemical functions, molecular size distribution, and dynamics of oligosaccharide mixtures.