In fully automated HPLC-SPE-NMR,17-20 compounds are detected
postcolumn by UV or MS and automatically trapped on SPE
cartridges, enabling multiple trapping and subsequent transfer of
the analytes to the NMR flow probe using a deuterated solvent.
The integrated SPE device thus allows the eluted compounds to
be concentrated prior to NMR, significantly improving the S/N
ratios and facilitating acquisition of 2D NMR data. The aim of this
work is to demonstrate the applicability of this novel technology
for the rapid characterization of constituents of plant extracts.
Kanahia laniflora (Forssk.) R. Br. (Apocynaceae-Asclepidoideae)
is distributed in tropical and subtropical Africa and is
used by local populations to treat convulsions associated with
malaria, headaches, epilepsy, and stomach pain.21-24 Previous
phytochemical studies on the roots of K. laniflora showed the
presence of small quantities of cardenolides as well as larger
amounts of pregnane glycosides.25,26 Chemical tests on different
parts of the plant have also suggested the presence of flavonoids.27
Within the same study, the biological evaluation of K. laniflora
revealed an indication of sympathetic stimulation, CNS depression,
diuretic activity, peripheral vasodilatation, and slight psychotropic
activity and metabolic poisoning.27 In the present study, we have
applied high-performance liquid chromatography combined with
diode array detection, solid-phase extraction, and NMR spectroscopy
(HPLC-DAD-SPE-NMR) for the efficient identification of the
main constituents of crude extracts of various parts of K. laniflora.