Regulatory issues relating to herbal products - Part 3: Quality and its determination

The concept of quality in the manufacture of herbal products is directed toward ensuring that the required standard of product is attained through processes that involve good manufacturing practice and quality control. This article reviews the need for quality assurance of herbal products, approaches taken by regulatory authorities in Europe to address this issue, and analytical methods applicable to the evaluation of herbal products. The natural ingredients that are used to prepare herbal products give rise to problems that are not encountered with conventional medicinal products. Quality standards are applied to both starting materials and finished products. Pharmacopoeial monographs, even when not forming part of official compendia, lay down criteria for analytical testing, including materials and methods, test limits, and acceptance ranges for results. Analytical tests are employed to establish the identity of the plant material or of the active principles, the content of active principles or characteristic marker compounds by assay, and the purity of the product by exclusion of specific adulterants or contaminants. Advances in instrumentation and test methods provide the analyst with powerful tools to determine the level of quality. Nevertheless, there still exist limitations to testing because of the complex and variable nature of the herbal ingredients. The standards and requirements for quality of herbal products as applied in the European Union are also intended to provide further assurances on the efficacy and safety of products.