The application strategies of non-uniform sampling in the structure elucidation of small molecule compounds—an instantiation using fuziline

Two-dimensional nuclear magnetic resonance (2D NMR) is a widely used technique for structural analysis of small molecular compounds. It can obtain information about the hydrogen-hydrogen correlation, hydrogen-carbon single bond correlation, hydrogen-carbon remote correlation, and hydrogen-hydrogen spatial arrangement of compounds. Thus, 2D NMR has an irreplaceable role in the structure elucidation of small molecular products. However, the sample amount of trace components in phytochemical research is very low, and the traditional sampling method (uniform sampling) has problems of poor spectral quality and too long measure time. Increasing the number of scans results in several hours of the acquisition time for a single two-dimensional spectrum, which in turn causes strain on the NMR machine. The non-uniform sampling (NUS) technique can shorten the acquisition time to a large extent and not affect the quality of 2D NMR data, which greatly improves the efficiency of 2D NMR acquisition. In this paper, fuziline, a small molecular compound in the lateral roots of Aconitum carmichaelii was selected as the research object. Its ¹H-¹³C HSQC, ¹H-¹H COSY, HMBC, and NOESY spectra were acquired by US and NUS methods, respectively. By comparing the integral values of NMR signals of three chemical groups in fuziline, it is confirmed that the NUS technique has the advantages of improving the quality of 2D NMR spectra and shortening the acquisition time in structure elucidation of small molecule compounds. In HMBC spectrum, it was further confirmed that NUS technology can improve the quality of the 2D spectra and the signal resolution. This indicates that NUS technology can improve the efficiency and reliability of the structure elucidation of small molecule compounds.