Application of capillary‐scale NMR for the structure determination of phytochemicals

Employing a capillary-scale NMR probe enables the miniaturisation of structure determination and de-replication of purified natural products from plants using only 5–100 µg of material. Approximately 5 µg are required to perform one-dimensional proton and two-dimensional homonuclear (COSY and NOESY) NMR experiments; some 30 µg are needed to acquire HMQC- or HSQC-NMR spectra; ca. 75–100 µg are necessary to measure HMBC-NMR spectra; and around 200 µg of a compound are needed to perform 13C- and DEPT-NMR experiments. In order to illustrate the integration of the outputs from high-throughput natural product chemistry methods with the capabilities of the state-of-the-art CapNMR™ technology, the preparation of a natural product library from the extract of Penstemon centranthifolius, and the subsequent isolation, purification and structure determination of six known iridoid glycosides with 25–300 µg of material are presented. Copyright © 2005 John Wiley & Sons, Ltd.