Abstract
Studying herbal products derived from local and traditional knowledge and their value chains is one of the main challenges in ethnopharmacology. The majority of these products have a long history of use, but non-harmonized trade and differences in regulatory policies between countries impact their value chains and lead to concerns over product efficacy, safety and quality. Veronica officinalis L. (common speedwell), a member of Plantaginaceae family, has a long history of use in European traditional medicine, mainly in central eastern Europe and the Balkans. However, no specified control tests are available either to establish the quality of derived herbal products or for the discrimination of its most common substitute, V. chamaedrys L. (germander speedwell). In this study, we use DNA metabarcoding and high performance liquid chromatography coupled with mass spectrometry (HPLC-MS) to authenticate sixteen V. officinalis herbal products and compare the potential of the two approaches to detect substitution, adulteration and the use of unreported constituents. HPLC-MS showed high resolution in detecting phytochemical target compounds, but did not enable detection of specific plant species in the products. DNA metabarcoding detected V. officinalis in only 15% of the products, whereas it detected V. chamaedrys in 62% of the products. The results confirm that DNA metabarcoding can be used to test for the presence of Veronica species, and detect substitution and/or admixture of other Veronica species, as well as simultaneously detect all other species present. Our results confirm that none of the herbal products contained exactly the species listed on the label, and all included substitutes, contaminants or fillers. This study highlights the need for authentication of raw herbals along the value chain of these products. An integrative methodology can assess both the quality of herbal products in terms of target compound concentrations and species composition, as well as admixture and substitution with other chemical compounds and plants.
Highlights
Traditional herbal medicines play an important role in meeting healthcare needs around the world, and complementary and alternative medicines based on these are gaining in importance in many industrialized countries as a perceived healthy alternative to synthetic pharmaceuticals (World Health Organization, 2013)
High-Performance Liquid Chromatography-Mass Spectrometry (HPLC-MS) is useful for qualitative and quantitative analysis of constituents in medicinal plants and herbal products and its use has increased in recent years (Steinmann and Ganzera, 2011; Bansal et al, 2014), but constraints are the expensive chemical reference standards, sensitivity to the type of raw material and manufacturing process, and lack of resolution in distinguishing plant species (Bansal et al, 2014)
Our HPLC-MS results show that distinction of V. officinalis from other Veronica species based on the targeted iridoid glycosides, aucubin, catalpol, veronicoside, and catalposide is difficult in pure products, and impossible in multiple ingredient products
Summary
Traditional herbal medicines play an important role in meeting healthcare needs around the world, and complementary and alternative medicines based on these are gaining in importance in many industrialized countries as a perceived healthy alternative to synthetic pharmaceuticals (World Health Organization, 2013). Crisan et al (2001, 2011) report histological, anatomical and phytochemical characters that distinguish V. officinalis and V. chamaedrys and propose a rapid differentiation method using thin-layer chromatography (TLC) of species-specific phenyl-propanoic compounds These analytical methods enable chemical identification of some target compounds, but cannot rule out that other Veronica species, or mixtures thereof, might be present in the investigated products. Substitution of V. officinalis with V. chamaedrys would be fraudulent from a commercial perspective, but would leave anticipating consumers with a herbal product without proven therapeutic activity We approach this hypothesis using DNA metabarcoding and HPLC-MS to authenticate and detect species diversity in European Veronica herbal products, and aim to answer the following research questions: (1) Can HPLC-MS be used to distinguish V. officinalis from V. chamaedrys and to identify exclusive presence of V. officinalis in herbal products?; (2) Can DNA metabarcoding be used to test for the presence of V. officinalis in herbal products, to detect substitution and adulteration for other Veronica species and/or presence of other off label plant species?
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