to achieve therapeutic goals. This leads to complications in labelling. One way manufacturers have attempted to indicate strength is to engage in standardization to a marker compound. However, standardization has not been achieved yet: different companies use different markers, or different levels of the same markers, or different methods of testing for marker compounds. For instance, St John's wort is often standardized to the hypericin which is now known not to be the "active ingredient" for antidepressant use. Other companies standardize to hyperforin or both, although there may be some 24 known possible active constituents. Many herbalists believe that the active ingredient in a plant is the plant itself. See also Formulation Medication Pharmakos Regulation of therapeutic goods Northeast of England Process Industry Cluster References External links Pesticide Active Ingredient Fact Sheets - National Pesticide Information Center Pharmacology Life sciences industry cs:Léčivo#Léčivá látka