Wie ungesund sind diese Substanzen?

This is about the yellow pond rose (Nuphar lute). This allows you to move in the area of obscure and badly researched active ingredients.

The effect on blood pressure seems to be known, with nupharin having a lower blood pressure and deoxynupharidine having a higher blood pressure. In experiments, the root should have been used to obtain an agent which had an impact on mice, dogs and eels. A toxicologe can perhaps make more concrete statements about harmfulness on the basis of the chemical structure.

Anyone who experimentes with poorly researched substances should have internalized the basics of Safer Use and be extremely careful. Use is at your own risk. This is work for pioneers (or experimental rabbits).
Also note that this is a natural product. Depending on the growth conditions, it may be that more or less of the different ingredients are formed. Precise dosing is not possible.