A review on new research on quality control of botanicals presented at the 65^th Annual meeting of the Society for Medicinal Plant and Natural Products Research (GA) in Basel, Switzerland

Keywords: adulteration, buckwheat, Chinese St. John’s wort, DNA barcoding, Fagopyrum esculentum, ginkgo, Ginkgo biloba, HPTLC, Hypericum perforatum, Japanese sophora, NMR, Sophora japonica

The 65^th annual meeting of the Society for Medicinal Plant and Natural Product Research (also known as Gesellschaft für Arzneipflanzenforschung, GA) took place in Basel, Switzerland, from September 3-7, 2017.

Organized by Matthias Hamburger and his staff from the Institute of Pharmaceutical Biology, Department of Pharmaceutical Sciences at the University of Basel, the GA meeting was attended by ca. 600 participants. The scientific program included three pre-symposium workshops, five plenary lectures, five award lectures, 96 contributed short lectures, and close to 500 poster presentations. Many presentations focused on drug discovery on a wide variety of biological targets using materials predominantly from plants, but also from fungal, microbial, and marine sources. Contributions on analytical methods and quality control of botanical ingredients were rare, and mainly presented as short lectures during the quality control session on September 7, 2017. Below are summaries of two presentations that may be of interest.

Reviewed: Frommenwiler D, Booker A, Heinrich M, Reich E, Cañigueral S.

Quality assessment of Ginkgo biloba supplements based on a single HPTLC Method.

Débora Frommenwiler from Camag presented newly developed high-performance thin layer chromatography (HPTLC) methods to detect adulteration of ginkgo (Ginkgo biloba, Ginkgoaceae) extracts. Several reports on the authenticity of commercial ginkgo extracts have shown that many of these contain flavonoids from extraneous sources, including pure rutin, quercetin, or flavonoid-rich extracts from buckwheat (Fagopyrum esculentum, Polygonaceae) or Japanese sophora (Sophora japonica, syn. Styphnolobium japonicum, Fabaceae).¹

The focus of this project was to obtain a better characterization of the adulterants, mainly through the use of additional detection modes. Beside added rutin and/or quercetin, the modified HPTLC method allowed detection of buckwheat and flower and leaf extracts of Japanese sophora. Using a reference solution of known concentrations, the levels of quercetin (≤ 0.5%) and the presence of genistein as markers for adulteration with Japanese sophora were verified.

A total of 35 commercial samples (included in a previous paper by the same group)² were subjected to quantitative analysis of total flavonoid glycosides by HPLC according to the monographs of the United States Pharmacopeia (USP) and the European Pharmacopoeia (EP). Twelve samples were in compliance with the total amount of flavonol glycosides specified in the monographs. However, ten of those had elevated levels of quercetin in the HPTLC fingerprint.

The advantages of the proposed HPTLC method for authentication of ginkgo extracts are that the same chromatographic conditions can be used for the assays, and that the additional detection method allows detection of admixture with Japanese sophora fruit based on a characteristic band in the chromatographic fingerprint.

References:

1. Gafner S. Ginkgo extract adulteration in the global market: a brief review. HerbalGram. 2016;109:58-59.
   
2. Booker A, Frommenwiler D, Reich E, Horsfield S, Heinrich M. Adulteration and poor quality of Ginkgo biloba supplements. J Herb Med. 2016;6(2):79-87.

Reviewed: Scotti F, Purvi M, Masiero E, et al. Hypericum perforatum – a comparison of commercial samples using DNA-barcoding and chemical approaches.

Francesca Scotti from University College London School of Pharmacy presented the results of an investigation into the authenticity of 20 commercial products labeled to contain St. John’s wort (Hypericum perforatum, Clusiaceae). The project combined chemical and genetic methods: nuclear magnetic resonance (NMR)-based metabolomics with subsequent principal component analysis (PCA), high-performance thin-layer chromatography (HPTLC), and DNA-barcoding.

HPTLC analysis showed that 10 samples (50%) were made with St. John’s wort, while the other 10 displayed a different fingerprint and were identified as “Chinese St. John’s wort”. The results from the NMR-PCA analysis confirmed the HPTLC results, clustering the “Chinese St. John’s wort” separately from St. John’s wort. Only nine samples yielded suitable DNA sequences for genetic identification: based on these genetic tests, the DNA sequences obtained for “Chinese St. John’s wort” corresponded to those of authentic H. perforatum, suggesting that materials from China may represent a different chemotype of St. John’s wort. Additional genetic work will be carried out to confirm these initial findings and to conclusively establish the identity of the plants used to make “Chinese St. John’s wort” extracts.