Determination of the conversion factor for silymarin - a solution for the problems associated with new assay methods in the pharmacopoeia.

In pharmacopoeial monographs for herbal drugs and herbal preparations, conventional assay methods such as colorimetry or spectophotometric assays are often replaced by modern, more specific and reliable methods, e.g. liquid chromatography (LC). However, existing dosage recommendations in the monographs on efficacy and safety of herbal medicinal products which are an important basis for licensing procedures do not refer to the mandatory new methods but to the existing photometric methods. The laboratory comparison of the determination of silymarin of Milk Thistle extract shows that a conversion factor can be calculated which allows a correlation between the new and the existing method. It is suggested that this factor should be included in the Ph. Eur. monograph on Milk Thistle extract, allowing reference to dosages given in official monographs (e.g. ESCOP, HMPC). The solution to use a conversion factor should also be applied to other herbal drugs and herbal preparations, especially for standardised extracts.

Determination of naphthodianthrones in plant extracts from Hypericum perforatum L. by liquid chromatography-electrospray mass spectrometry.

The determination of the naphthodianthrone constituents in extracts of dried blossoms of Hypericum perforatum L. by combined HPLC-electrospray mass spectrometry is described. Hypericin (1), pseudohypericin (2) and their precursor compounds produce intensive negative quasi-molecular ions by deprotonation provided a non-acidic eluent system is used in the HPLC separation. From the [M-H]- ions formed in the electrospray ionization process characteristic daughter ion spectra can be obtained by collisional activation which have been studied by tandem mass spectrometry.