Herbal drugs contain a variety of chemical substances from which their total of the active ingredient of the drug comes (see phytotherapy). The chemistry of the drug is therefore of major interest and the subject of scientific research worldwide (phytochemistry). The ingredient spectrum of a variety of drugs, particularly of drugs used medicinally in Europe, is already well researched. There are still many plants around the world whose chemical makeup is still a mystery. Far too little is known about the contribution of individual compounds to the efficacy of the drug. Therefore, the chemical features of the drug are only represented very briefly in the monographs of this lexicon. The interested reader of the subject may wish to use the further reading service.