NMR as Integrative or Alternative Analytical Tool for the Quality Control of Herbal Drugs and their Preparations

In the last decades, the use of products of botanical origin has remarkably increased in the global market but only a limited percentage is represented by the category of herbal medicinal products (HMPs) whose purity, safety, potency and efficacy is guaranteed by the regulatory authorities. By contrast, a substantial portion of herbal global market is based on other types of botanical preparations, in many cases not subjected to quality control of national agencies due to a lack of specific regulations. As a consequence, there are growing instances of herbal remedies that have been adulterated or substituted with other plant materials and/or conventional medicines which have reinforced the need for adequate quality control.

Authentication, quality control and stability testing of botanical preparations is generally achieved and is well established through the use of HPLC, HPTLC, capillary GC, with specific detectors (UV/VIS, RI, and coupled systems such as MS) which allows for the qualitative and quantitative determination of the composition of the markers or active substances. GLC analysis is limited to volatile metabolites (or those that can be made volatile) while HPLC methods are better suited for compounds with conveniently detectable chromophores or functional groups, while detection and identification of unexpected or unknown metabolites, and/or adulterants still requires extensive efforts with either method, even with the inclusion of mass spectrometers.

The recent advances in NMR methodology offer a means to overcome all of these limitations, with the exception of very low detection limits. The range of compounds that can be analyzed is not limited by their volatility, presence of chromophores, or polarity. Furthermore, NMR measurements are not destructive, which allows samples to be subsequently analyzed by other methods [1 – 4]. NMR analysis represents an integral part of quality control as presented by some unpublished results and studies reported in the literature. References: [1] Bilia AR (2013) “NMR as Analytical Tool for Crude Plant Extracts” Handbook of Chemical and Biological Plant Analytical Methods. John Wiley & Sons, Ltd., The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, United Kingdom. [2] Bilia AR, et al. (2002) J Agric Food Chem, 50: 5016 – 5025. [3] Bilia AR et al. (2002) J Pharm Biom Anal, 30: 321 – 330. [3] Bilia AR, et al. (2001) J Agric Food Chem, 49: 2115 – 2124.