Comprehensive 1 H and 13 C NMR assignment of 13 protobassic acid saponins

This study aimed to carry out complete 1 H and 13 C NMR assignment of 13 protobassic acid saponins, including arganins A–C ( 1 – 3 ) and F ( 4 ), butyrosides B–D ( 5 – 7 ), tieghemelin ( 8 ), 3′‐ O ‐glucosyl‐arganin C ( 9 ), Mi‐saponins A–C ( 10 – 12 ), and mimusopsin ( 13 ), recorded in methanol‐ d 4 . This was accomplished by the analysis of high‐resolution one‐dimensional (1D) NMR ( 1 H and 13 C), two‐dimensional (2D) NMR ( 1 H– 1 H COSY, HSQC, and HMBC), and selectively excited 1D TOCSY spectra. Before this study, 1 H and 13 C NMR data of arganins A–C ( 1 – 3 ) and F ( 4 ) were partially assigned. Our effort leads to their complete assignment, especially the glycon residue, and revises some reported data. Some revisions of the 1 H and 13 C NMR data in the glycon part of butyroside C ( 6 ), tieghemelin ( 8 ), Mi‐saponin A ( 10 ), and mimusopsin ( 13 ) were made. Those data of butyrosides B and D ( 5 & 7 ) and Mi‐saponin B ( 11 ), which had not been recorded in methanol‐ d 4 , are provided. In addition, the 1 H and 13 C NMR data of Mi‐saponin C ( 12 ) are reported for the first time. These data, being recorded in methanol‐ d 4 , should be more friendly for use as a reference for identifying the related triterpenoid saponins.