Preparative isolation and structural characterization of sucrose ester isomers from oriental tobacco

To date, the structures of the sucrose tetraester (STE) isomers, a main kind of sucrose esters (SEs) in Solanum, have not been conclusively assigned. In this study, three groups of STE isomers with the molecular weight 650, 664 and 678 (designated as STE I, STE II and STE III, respectively) have been isolated and purified from the oriental tobacco-Komotini Basma using a semi-preparative RP-HPLC method. The full characterization of the isomers in the three groups of STE were investigated for the first time by MS (HRMS, MS2) and NMR (1H, 13C, HSQC) spectroscopy combined with alkaline hydrolysis and STE derivation experiments. The STE III (a single compound) was confirmed as a known sucrose tetraester. Furthermore, the STE II was found to contain three isomers and the structures were first unambiguously established as 6-O-acetyl (2,3 or 2,4 or 3,4)-di-O-3-methylvaleryl-(4 or 3 or 2)-O-2-methylbutyryl-α-d-glucopyranosyl-β-d-fructofuranoside. Finally, the STE I was discovered to contain seven isomers and the structures were elucidated as 6-O-acetyl (2 or 3 or 4)-O-3-methylvaleryl-(3,4 or 2,4 or 2,3)-di-O-2-methylbutyryl-α-d-glucopyranosyl-β-d-fructofuranoside, 6-O-acetyl (2 or 3 or 4)-O-3-methylvaleryl-(3,4 or 2,4 or 2,3)-di-O-isovaleryl-α-d-glucopyranosyl-β-d-fructofuranoside and 6-O-acetyl (2,3 or 2,4 or 3,4)-di-O-3-methylvaleryl-(4 or 3 or 2)-O-isobutyryl-α-d-glucopyranosyl-β-d-fructofuranoside (one of the 3 isomers).

Graphical abstractA series of sucrose tetraesters (STE) have been isolated from the oriental tobacco-Komotini Basma after ultrasonic assistant extraction and purified by semi-preparative RP-HPLC. The MS (HRMS, MS/MS) and NMR (1H, 13C, H-COSY, HSQC) spectra along with GC/MS analysis for derivation products of STEs and their hydrolysis products provided the requisite structural evidence.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A semi-preparative HPLC method for isolation of STEs isomers was established. ► Three groups of STE isomers were isolated and purified, respectively. ► The purity of all the three groups of STEs isomers exceeded 99%. ► The structural identification was achieved by NMR and HRMS spectra. ► The structures of isomers in the three groups of STEs was confirmed or elucidated.