10.3.1 Determination of the Flavonoids
Substances that interfere with the analysis of flavonoids (e.g., carotinoids) are usually removed by extraction. It has to be taken into account that the majority of apolar flavonoids will also be removed in this step, e.g., by the extraction with carbon tetrachloride . Moreover, extraction by hot water results in 30-45% lower values for flavonoids compared to methanol extraction. It is therefore not possible to avoid the co-extraction of chlorophyll and related substances by using water.
The photometric determination of flavonoids has many advantages, although the absolute values are actually about 20-30% higher. Other methods as suggested by Reichling et al. showed no improvement . The absolute content of flavonoids ranged between 1.0 and 2.5% in a study of 102 commercially available plants and determination according to References 106 and 17. Twelve samples of material of different origin cultivated by Schilcher showed values between 0.3 and 2.96% [121, 122].
10.3.2 Paper Chromatography (pc) and Thin-Layer Chromatography
Flavonoids have musculotropic and neurotropic effects on spasmolysis. Therefore, there is a pharmacological interest in the content of flavonoids. It is known that flavonoid biosynthesis is influenced by environmental factors. The identification and quantification of flavonoids elucidates the chemo-taxonomy of the plant material.
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