Abstract: Analysis of mixture is important in pharmaceutical studies, in which NMR can be a very useful method. In present study, the relative concentrations of aescin A, B, C and D in the mixture of sodium aescinate were determined with HPLC. ¹H and ¹³C NMR characteristics of these compounds were analyzed using band-selective 2D constant-time HMBC and other 2D NMR methods. The high resolution provided by the band-selective constant-time 2D experiment made correct assignments of almost overlapped resonant peaks from compounds with similar structures possible. The results of this study suggest that selective 2D NMR techniques can be used to facilitate the analysis of mixture.

Key words: NMR, chemical shift, sodium aescinate, band-selective constant-time HMBC