Characterization of an umbelliferose-derived disaccharide–isomelibiose– α-D-Galp-(1→2)-D-Glcp

Umbelliferose, α-D-Galp-(1→2)-α-D-Glcp-(1→2)-β-D-Fruf, is the main trisaccharide present in the plants of Apiaceae family (umbellifers). Umbelliferose can be hydrolyzed to generate a disaccharide–isomelibiose, α-D-Galp-(1→2)-D-Glcp, which accumulates sometimes in certain parts of these plants. However, till date no attempt has been made to characterize isomelibiose. Herein we have purified umbelliferose from fennel seeds and subjected it to partial acid hydrolysis to produce isomelibiose. 1D and 2D NMR experiments were performed for isomelibiose, along with the parental trisaccharide, revealing unique spectral characteristics. Hydrophilic interaction liquid chromatography (HILIC)-based chromatographic separation coupled with evaporative light scattering detector (ELSD) resulted in distinct elution pattern of umbelliferose and isomelibiose when compared with respective isomeric oligosaccharides. Thus, for the first time, the structural feature of isomelibiose was determined.