Medicinal Plants Classification Biosynthesis and ... - Index of

Non-Invasive Near Infrared Spectroscopic Techniques for the Characterization...
Ch
Charge
34
22
11
2
42
4.2. St. John´s Wort
Table 1. Validation and results of real samples
HPLCvalue:
(ng/µl)
0.219
0.222
0.197
0.210
0.245
NIR-value:
(ng/µl)
0.219
0.210
0.230
0.186
0.193
% H2O
80.38
80.83
80.25
81.33
79.69
% EtOH
15.7
15.2
15.7
14.5
15.7
St. John´s Wort extract is used for treatment of skin injuries, burns, neuralgia, for its
bactiostatic/bacteriocide activity and as a treatment for mild to moderate depression [21-27].
Hypericin and hyperforin are discussed as being the active antidepressant components in
Hypericum perforatum L. extracts, although it is still unclear how and why St. John´s Wort
extract works as an antidepressant [28-33]. It is commonly known that the extract acts as a
mild monoamine oxidase inhibitor and a strong serotonine reuptake inhibitor [34]. Hypericin
and hyperforin act as standards in the phytopharmaceutical industry. They are the main
representatives of the naphtodianthrone group. The lower concentrated
cyclopseudohypericine might be synthesized out of pseudohypericin [35]. Beyond the main
representatives of the phloroglucine derivative hyperforin, presence of isohypericin,
desmethylpseudohypericin, hypericodehydrodianthrone, pseudohypericodehydrodianthrone
and skyrin exist [37-39] (Figure 6).
Several analytical procedures have been established including UV-spectroscopy [40],
fluorescence microscopy [41], thin-layer chromatography (TLC) [43-45], liquid
chromatography (LC) [46-50], LC coupled to mass spectrometry (LC-MS) [51] and capillary
electrophoresis [52]. Special sample pre-treatment procedures include liquid-liquid extraction
(LLE) and solid-phase extraction (SPE) has been worked out [51]. As all these methods are
extremely time-consuming and peak-tailing effects in LC make quantitative determinations
difficult, NIRS offers a fast alternative for the simultaneous quantitation of
naphthodianthrones and phloroglucines.
Prior to analysis of spectra via NIRS a reference method based on LC, LC-MS and CE
must be established to enable quantitation of hyperforin and hypericin [53]. Optimisation of
LC parameters finally allowed analysing naphthodiantrones and phloroglucines in one single
run (Figure 7).
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