Medicinal Plants Classification Biosynthesis and ... - Index of

Non-Invasive Near Infrared Spectroscopic Techniques for the Characterization...
extracts were recorded in transflection mode using light fibre optics over a wavelength range
from 4008 to 9996 cm -1 with a resolution of 12 cm -1 . Ten scans were used for one average
spectrum to equilibrate in homogeneities. Figure 8a shows 80 original spectra of St. Johns
Wort extract samples. Calculation of the first derivative spectra (Figure 8b) allowed
identification of characteristic absorption bands. The most intensive band in the spectrum
belonged to the vibration of the second overtone of the carbonyl group (5352 cm -1 ), followed
by C-H stretch and C-H deformation vibration, the –OH vibration (4440 cm -1 ) and the –CH2
overtone (5742 cm -1 ). Normalisation allowed for minimisation of the baseline shift. In the
following all 80 extracts were analysed four-fold by LC for establishing the quantitative
regression model. Seventy percent of the spectra were randomly put into a learning-set and
30% into a validation-set. Five primary factors were necessary to reach the best calibration
equation. The robustness of the established NIRS model is high, which is demonstrated in
similarity of results for SEE and SEP: 0.52 and 0.50 µg mL -1 and 0.64 and 0.71 µg mL -1 for
hypericin and hyperforin, respectively. Accuracy is expressed in the bias. The values are 1.6
and 4.2E-14. So the LC-UV results correspond to NIRS on average. Calculation of the
regression equation for hypericin (Figure 9) and hyperforin (Figure 10) resulted in correlation
coefficients of 0.994 and 0.985, which are slightly smaller than the correlation coefficients of
the LC-UV method. The model can be used to predict the content of hypericine and
hyperforine in liquid St. John´s Wort extracts. Results show the possibility for
phytopharmaceutical industry to replace LC method, usually applied to determine hypericin
and hyperforine in the routine analysis, with NIR method, guaranteeing a high degree of
robustness and reproducibility. Due to less sensitivity of the NIRS method, it is evident that
for the analysis of the lower concentrated naphthodianthrones proto-, pseudo-, protopseudo-,
and cyclopseudohypericine as well as for the phloroglucine adhyperforine in particular LC
must be preferred. CE was found to be less reproducible. NIRS has the great advantage of
ensuring high sampel throughput and reduced costs. NIRS is a full spectrum method. It
cannot only determine the content of the naphthodianthrones and phloroglucines but also of
other analytes within one single measurement. Finally, also information about other
parameters concerning the quality of the extract, e.g. the solvent composition, etc., can be
gained.
4.3. Achillea Genus
The genus Achillea exhibits extraordinary ecological amplitude and ranges with great
morphological variation. It is hard to identify and discriminate its species due to its highly
morphological diversity and chemical homogeneity. Some species, such as Achillea
millefolium, ceretanica, collina, pratensis, etc., were recognized as one group, the Achillea
millefolium complex, for their high homogeneity and successful crossing [54,55]. According
to the species index of NCBI taxonomy, there are 65 species of Achillea, e.g. clypeolata,
collina, millefolium, nobilis, wilsoniana, etc. A large number of Achillea species is endemic
and restricted to certain regions in Europe or certain temperature areas in Asia. Only few of
the other species are growing over a wide geographical range.
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