ABSTRACT
Floral Essential Oil .............................................................. 368 9.5.2 LC-MS............................................................................................................................. 368
9.5.2.1
Ligusticum chuangxiong
.................................................................................. 368 9.5.2.2
Vernonia fastigiata
........................................................................................... 371 9.5.3 LC-NMR ......................................................................................................................... 373
9.5.3.1 Solvent Signals................................................................................................. 373 9.5.3.2 Stop-Flow Analysis .......................................................................................... 375 9.5.3.3
Stauranthus perforatus
..................................................................................... 377 9.5.3.4
Fraxinus
spp..................................................................................................... 377 9.5.3.5
Piper longum
.................................................................................................... 382 9.5.4 LC-NMR-MS .................................................................................................................. 385
9.6 Conclusions .................................................................................................................................. 385 References .............................................................................................................................................. 386
The bottleneck in natural products chemistry generally is separation/purification of compounds of interest from complex mixtures and structure elucidation of those compounds. Separation was addressed in Chapter 8
,
and in this chapter, we address the problems of structure elucidation. The most important tools for structure elucidation of natural products are
nuclear magnetic resonance
(
NMR
) (Günther, 1995) and
mass spectroscopic
(
MS
) (de Hoffmann and Stroobant, 2002) techniques. In addition,
infrared
(
IR
) and
ultraviolet-visible spectrophotometric (UV-Vis
) methods are of importance. In this chapter, we present NMR and MS in some detail, as well as provide overviews of IR and UV-Vis. We also include hyphenated techniques such as gas chromatography (GC)-MS, liquid chromatography (LC)- MS, and LC-NMR. These techniques provide separation methods coupled with structural (spectroscopic) information. Although a very powerful analytical method, x-ray crystallography is not covered (Stout and Jensen, 1989).
