Identity and Purity of Various Flavonoid-Containing Plant Extracts

2 Identity and Purity of Various Flavonoid-Containing Plant Extracts 

In the TLC analysis of dry extracts prepared from medicinal plants, the sample preparation is performed in a different way from that prescribed in the monographs for the drugs in the pharmacopoeias. Also, there is no binder in the recommended solvent system, and in these cases a validation of the new in-house method is certainly necessary. 

As this not only requires adequate experience of the user, but also adds a very time-consuming operation to the laboratory routine, the development of an optimized TLC method for the dry extract is often omitted. This is often the precise reason that TLC is discredited in comparison to other analytical methods. An example of a successful optimization of the parameters of various TLC systems for birch leaves is given in Table 10, and the chromatograms for these are shown in Fig. 48a-d. 

Flavonoid constituents are present in a number of drugs, and therefore a consistent sample preparation method is suggested in Document 12 together with a uniform TLC system for the dry extracts. In the sample chromatograms included with the testing procedure, there are five dry extracts and the separation of a drug. This should confirm that the chromatographic system chosen could also be used for this apphcation. 

Quantitative determinations require validated analytical methods (see Section 9.1). An example of this is the Assay by HPTLC of theophylline in an effervescent tablet [144], for which a proposal for a testing procedure has been prepared (Document 13). All the results of the validation, including the calibration function, chromatograms and spectra can also be found in [144]. Document 13 includes only Fig. 2, which shows the chromatograms of the standard solutions with and without the addition of auxUiary substances, a blank lane and the pure mixture of auxiliary substances. 

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Examples of the TLC investigation of stressed samples are shown in Fig. 92 (dex-panthenol) and in the testing procedme Identity and Purity of Various Flavonoid-Containing Plant Extracts is given in Section 9.4.2. 

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