Quality control of herbal drugs and preparations: The methods of analysis, their relevance and applications

Medicinal plants have been used for a very long time to improve human health; they are gaining increasing popularity globally as drugs, complementary and alternative medicines, food supplements, cosmetics and, more surprisingly, as medical devices. The complexity of herbs and extracts, supplied to such a wide range of markets and in different requlatory environments, raises major quality issues, increasing the need for appropriate analytical methods for their identification and standardization, but also for the detection of adulterants and contaminants. Customs laboratories are often confronted with herbal samples which pose a range of challenges, ranging from quality issues to safety and even legal issues. Selecting a relevant analytical method, from the many available (microscopy, spectrometry, spectroscopy, chromatography…), is a crucial point that mainly depends on the set analytical goals. This review aims to detail such analytical goals and their complexity to propose a selection of analytical methods likely fit for each purpose. Major limiting factors, such as herbal product naming, sampling and sample preparation are also discussed.