Separation, identification, and structural characterization of sucrose ester isomers from tobacco

Sucrose esters (SEs) are crucial tobacco smoke flavor precursors and play a significant role in tobacco's functionality. Due to their structural complexity, the separation and analysis of SEs in tobacco remain a major challenge, and massive structures of SEs have not yet been fully identified. In this study, the fractions enriched in SEs were obtained from oriental and flue-cured tobacco through a series of pretreatments, and two types of SEs (Types I and II) were distinguished by liquid chromatography-tandem mass spectrometry (LC-MSn) analysis, with Type II SEs newly characterized in tobacco. Five groups of main SEs were further purified using preparative high-performance LC (HPLC) coupled to an evaporative light scattering detector, and their structures were characterized by nuclear magnetic resonance spectrometry techniques including 1H, 13C, correlation spectroscopy, heteronuclear single quantum correlation, and heteronuclear multiple bond correlation. By combining LC-MSn and nuclear magnetic resonance spectrometry, the structures of eight SE isomers were finally proposed, of which four were newly identified. These findings further enhance the understanding of the structural diversity of SEs in tobacco, serving as a valuable reference for future research on the elucidation, synthesis, and metabolism of SEs.