Quality Standards for Herbal Drugs and Herbal Drug Preparations - Appropriate or Improvements Necessary?

Standards for quality control as defined in the European Pharmacopoeia contribute significantly to a consistent and high quality of herbal drugs, herbal drug preparations, and herbal medicinal products. The minimum content of single plant constituents is considered of high relevance. Therefore, nearly all monographs on herbal drugs or herbal drug preparations contain an obligatory assay. However, a critical evaluation of the data published for such assayed constituents reveals that in most cases these constituents have to be considered as purely analytical markers without correlation to quality or efficacy. Examples where the assay does not meet its objective support the need to adapt current quality standards. Moreover, the trend to increase the content of certain constituents may lead to significant modifications to traditional manufacturing processes. In order to initiate a scientific discussion, the role of the assay in the context of quality requirements, quality documentation in the manufacturing process, safety, and efficacy is discussed and possible alternatives to the single marker assay are examined.