Genetic and Chemical Analysis of Commercial Herbal Teas and Extracts Shows Substitution of Speedwell (Veronica officinalis) with Germander Speedwell (V. chamaedrys)

Reviewed: Raclariu AC, Mocan A, Popa MO, Vlase L, Ichim MC, Crisan G, Brysting AK, de Boer H. Veronica officinalis product authentication using DNA metabarcoding and HPLC-MS reveals widespread adulteration with Veronica chamaedrys. Front Pharmacol. 2017;8:378. doi: 10.3389/fphar.2017.00378.

Keywords: adulteration, DNA metabarcoding, Germander speedwell, HPLC-MS, speedwell, substitution, Veronica chamaedrys, Veronica officinalis

The aboveground parts of speedwell (Veronica officinalis, Plantaginaceae) are used in Europe (more widely in central Eastern Europe and the Balkans), mainly as an herbal tea for the treatment of coughs and other respiratory problems, and as a diaphoretic (to increase perspiration).¹ Speedwell is also used topically to promote wound healing. However, data on its efficacy is scarce, and the German Commission E issued a negative monograph (efficacy not sufficiently substantiated at the time of the review) for speedwell.²

The goal of this investigation was to determine the identity and evaluate the quality of commercial products labeled to contain speedwell. A total of 16 commercial products were obtained in herbal shops, supermarkets, and pharmacies mainly in Romania (N = 12), but also two products from both Austria and Poland. Products included 12 herbal teas, two extracts, one capsule, and one lozenge. Seven samples were single-ingredient products, while the remainder contained between three and 19 listed herbal ingredients according to the label.

The identity of the ingredients was established using the nuclear ribosomal Internal Transcribed Spacer (ITS) region as genetic barcode. Sanger sequencing was used to distinguish between V. officinalis and germander speedwell (V. chamaedrys), while DNA metabarcoding (using next-generation sequencing technology) allowed identification of additional plant species in the commercial products. Identity was based on comparison of the DNA sequences with those deposited in GenBank (including 14 samples of V. officinalis and seven of V. chamaedrys collected by the authors). In addition to the genetic tests, four iridoid glycosides (aucubin, catalpol, catalposide, and veronicoside) were quantified by high-performance liquid chromatography coupled to mass spectrometry (HPLC-MS) in four authenticated samples of both V. officinalis and V. chamaedrys, and in the commercial products.

Veronica officinalis was found in two commercial products (12.5%), while V. chamaedrys was identified in eight (50%) of the 16 samples. Three products (two teas and the lozenges) did not provide any useful DNA sequences. Interestingly, veronicoside, which was present in all four reference samples of V. officinalis, but absent in authentic V. chamaedrys samples, was detected in five commercial products (31.3%), including one of the teas for which no DNA sequence was obtained. Since veronicoside has been isolated from species other than V. officinalis, it is possible that some products contained this iridoid glycoside due to the presence of an unidentified plant. On the other hand, it cannot be excluded that the V. officinalis DNA in some of the products was deteriorated to the extent that no useful sequence information could be obtained.

Comment: The publication raises concerns about the identity of the speedwell products analyzed. All the products containing V. chamaedrys were sold in Romania, while the authentic products were from Austria and Poland, possibly reflecting regional dominance of the species used in trade. It is commendable that the authors used an orthogonal approach, i.e., HPLC-MS, to analyze the samples, in addition to the genetic methods. However, the manuscript would have benefited if the results of the genetic and chemical approaches would have been compared and discrepancies discussed thoroughly. The presence of veronicoside in a number of samples where no V. officinalis DNA was found warrants an explanation. Another important point that was not discussed is the fact that V. chamaedrys is used medicinally as well, e.g., in Austria, with indications similar to V. officinalis. According to Vogl et al³ both V. officinalis and V. chamaedrys elicited a modulating activity on pro-inflammatory mediators in vitro, which suggests that these herbs may be beneficial in the treatment of respiratory infections. Additionally, Grieve assigns the common name “speedwell” specifically to V. chamaedrys, and cites its use for wound healing and coughs in a manner similar to V. officinalis, showing that different species of Veronica were commonly referred to generically as speedwell.⁴ Both species are allowed to be used as “Listed Medicines” by the Therapeutic Goods Agency of Australia. Only V. officinalis with the Standardized Common Name speedwell is listed in Herbs of Commerce. Veronica chamaedrys is also used medicinally in Romania. According to Dihoru and Boruz, higher amounts of V. chamaedrys are collected for medicinal purposes in Romania than V. officinalis.⁵ Some authors consider the two species interchangeable,³ while others believe that V. chamaedrys is of lesser value.⁶ Chemically, the two species both contain iridoid glycosides (with aucubin and catalpol as important compounds), hydroxycinnamic acid derivatives, and flavonoids, but the quantities of individual components vary substantially between the two species.⁷ Therefore, these two species can be distinguished by chemical analysis, e.g., HPTLC or HPLC-UV, as well. Despite the similarity of the common name, germander speedwell should not be confused with germander (Teucrium chamaedrys, Lamiaceae), a plant that is known for its hepatotoxic furano neo-clerodane diterpenes.

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