Combined use of liquid chromatography–nuclear magnetic resonance spectroscopy and liquid chromatography–mass spectrometry for the characterization of an acarbose degradation product

Directly coupled LC–MS and LC–NMR were applied to identify and structurally characterize an acarbose degradation product A in acidic media. A comparative analysis of the stop-flow LC–NMR (1H and TOCSY) and LC–MS data provided evidence that A is structurally related to acarbose, differing from the parent compound in a number of subunits present in the molecule. Spectral analysis revealed that A was the α-glucosidase inhibitor amylostatin XG. Complementary information obtained from the two methods led to the structural elucidation of A which was later corroborated by high-resolution NMR spectroscopy of the isolated molecule.