Viscotoxins, mistletoe lectins and their isoforms in mistletoe (Viscum album L.) extracts Iscador

The purpose of the following study was to evaluate the presence of the most frequently investigated pharmacologically active mistletoe compounds, viscotoxins (VT) and mistletoe lectins (ML), in European mistletoe Viscum album L. and in the pharmaceutical mistletoe preparations Iscador. Quantitative analysis of the VT isoforms A1, A2, A3, B, 1-PS, and U-PS in fresh mistletoe plant material from the three European subspecies of V. album, during fermentative extraction of mistletoe and in Iscador showed that the pharmaceutical proceeding specific for the preparation of Iscador warrants a high yield of VT. No degradation or transformation of VT during the production process became apparent. The VT compositions of the three host specific European subspecies of V. album, ssp. album, ssp. abietis, and ssp. austriacum, showed characteristic differences. They ensured the identification of the subspecies specific types of Iscador. ML contents of mistletoe extracts were reduced during fermentative extraction. The quantified contents of total ML were 261 +/- 9.3 ng/ml in Iscador M 5 mg spec. and 391 +/- 18.3 ng/ml in Iscador Qu 5 mg spec. Binding of ML to the glycoprotein asialofetuin (type 1) was found to be temperature dependent. Binding activity was increased to 250 % (ML I) and 410 % (ML II and ML III) respectively by decreasing temperature from 30 degrees C to 4 degrees C. 95% of ML could be eliminated from Iscador by affinity chromatography with immobilised glycoproteins at 0 degrees C. Quantitative extraction of ML from the crude extract and their analysis by SDS-PAGE revealed the presence of about 30 % ML I, 20% ML II, and 50% ML III in Iscador M 5 mg spec. and Iscador Qu 5 mg spec. The annual course of concentrations of ML and VT in the leaves of V. album showed maximal ML contents in December and culminaton of VT in June. Seasonal fluctuations of the composition of mistletoe imply the importance of fixed harvesting seasons.