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Biosynthesis and Evolution of cardiac glycosides

The Wooly Foxglove (Digitalis lanata Ehrh.) is an important medicinal plant and the cardiac glycosides (cardenolides) isolated from its rosette leaves are used in the treatment of cardiac insufficiency in man. In many respects, this plant serves as an experimental model to study synthesis, transport, and degradation of cardenolides. The biosynthesis of the cardiac glycosides is not well understood. Hence, the final aim of our research is to work out the enzymatic basics of the cardiac glycoside biosynthesis in order to make those biosynthetic steps accessible for a molecular-genetic adaptation. These topics combine chemical synthetic and biochemical techniques. Currently we are investigating the following steps: butenolide ring formation, pregnane-21 hydroxylation, pregnene oxido-reductases and pregnane isomerases.

Enzymes of medicinal herbs: quality of phytopharmaceuticals and production of technical enzymes

It has been proven by clinical studies or medical experience that many drugs used in modern phytotherapy (phytopharmaceuticals) are effective. In the search for so-called active substances and in the efforts made to explain the efficacy of a phytopharmaceutical, products of secondary plant metabolism, for which a biological effect has been proven in adapted models, have been the principal objects of study up to now. The relevance of plant-specific enzymes in the quality control and efficacy of herbal drugs and preparations has not yet been well studied. However, it is known that plant enzymes can be active even after harvesting and drying of the plant material. Some of these enzymatic activities have been used in technical processes. As for herbal medicinal products, plant enzymes can alter the quality of raw materials, e.g. by influencing the content of active ingredients. The activity of such enzymes can have either negative or positive effects. Although such processes have often been observed, the related biochemical reactions have not been well characterized. At present we are particularly interested in the following enzymes: polyphenole-oxidases, β-glucosidases

Phythaemagglutinins (Lectins)

Lectins represent a very large group of substances existing in nearly all organisms. Lectins are proteins that specifically recognize certain carbohydrate molecules (free or bound to cell surfaces) and have the ability to bind them. In addition, lectins are able to agglutinate cells like erythrocytes, lymphocytes, or malignant cells. Some lectins, like those from Mistletoe (Viscum album), are highly toxic. The toxic effect of lectins suggests, they might be used in tumor therapy. This has been a point controversy for years, because a suitable method for standardizing of these therapeutically used drugs does not exist. The adaptation of herbal drugs with variable contents (the lectin content is usually subject to seasonal variations) raises the question of whether the drug is harmless and clinically useful. Analysis and standardization of lectin preparations is not a trivial matter. The methods must be very reliable, sensitive, and reproducible. To establish reliable protocols, we used the following methods: SDS-PAGE, ELLA, ELISA, haemagglutination, Western blot and HPLC.

Plant cell and tissue culture

Different techniques of micropropagation can be used for the maintenance, propagation, and cloning of important medicinal plants. We apply the following methods to solve different problems (conservation, propagation, and biochemical studies): In-vitro-cloning of valuable unique plants by meristem-cultures, Callus cultivation aiming at organogenesis, Permanent cell and tissue cultures.