Medicinal Plants Classification Biosynthesis and ... - Index of

Non-Invasive Near Infrared Spectroscopic Techniques for the Characterization...
4) Standard error of prediction (SEP), i.e., the counterpart for the test-set samples. SEE
and SEP should be as small as possible.
1
SEP xn
yn
N
5) The correlation coefficient (R 2 ) should approach 1.
Bias
4. Characterization of Medicinal Plants and Their
Constituents
In the following the potential of NIRS for the qualitative and quantitative
characterization of medicinal plants and their constituents including secondary plant
metabolites and leading compounds down to the ppm-level are discussed. The suitability to
analyse simultaneously chemical and physical properties supported by chemometrical
approaches is shown by three selected examples: Flos Primulae veris is used due to its antiinflammatory
properties, St. John´s Wort for the treatment of mild and moderate depressions;
Achillea is used for the treatment of gastrointestinal diseases.
4.1. Flos Primulae Veris
Flos Primulae veris is used due to its flavonoid content related anti-inflammatory
properties and its effect as an expectorans for the treatment of a cold and related sinusitis. In
Figure 2 a general strategy scheme for NIR-analysis of compounds in liquid plant extracts is
shown. For the control of the Primulae veris Flos content the leading compound 3´,4´,5´trimethoxyflavone
was determined by reversed-phase liquid chromarography (RP-LC), which
was used as a reference method [20]. After optimization of the temperature and the optical
thin layer 220 NIR spectra of 44 charges were recorded in the transflection mode with the
spectrometer. Mathematical pre-treatment and statistical analysis were carried out by
performing partial least squares regression (PLS). In Figure 2 the possibility to control other
plants in a multi plant component extract is illustrated.
Recording the NIR-spectrum (Figure 3a) and calculation of its 1 st derivative spectrum
allowed to identify characteristic absorption bands. The most intensive band in the spectrum
belonged to the vibration of the 2 nd overtone of the carbonyl group (5352 cm -1 ), followed by
the C-H stretch and C-H deformation vibration of ethanol (7212 cm -1 ), the-OH vibration of
water and ethanol (4440 cm -1 ), the -CH2 overtone (5742 cm -1 ) and the –CH2-/-CH3 overtone
(5808 cm -1 ) (Figure 3b). All recorded spectra were normalized and transformed to their first
derivative before calculating the PLS model. Thereby, normalization allowed minimizing
shifts in the baseline.
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