Qualitative and Quantitative Characterization of Two Licorice Root Species (Glycyrrhiza glabra L. and Glycyrrhiza uralensis Fisch.) by HPTLC, Validated by HPLC and DNA Sequencing

The herbal drug licorice root may be derived from the plant species Glycyrrhiza glabra L., Glycyrrhiza uralensis Fisch, and/or Glycyrrhiza inflata Bat. which are morphologically, chemically, pharmacologically, and toxicologically similar. However, if an ingredient of a dietary supplement is identified as a certain species and labeled as such on the product, appropriate analytical methodologies are required to assure the authenticity. Using high-performance thin-layer chromatography (HPTLC), we were able to distinguish clearly between G. glabra and G. uralensis, the most commonly used species, which allowed us to check the corresponding label claims of twenty-six dietary supplements. Two samples of G. inflata Bat., which were available for the study, were not distinguished from G. glabra by this method. Our investigation revealed that five of the twenty-eight samples made a wrong label claim. The HPTLC results were confirmed by deoxyribonucleic acid (DNA) barcoding. For the quantitative analysis of the marker 18 beta-glycyrrhizic acid in licorice root, we modified our HPTLC method for base-line separation of the peaks which guaranteed accurate results. Moreover, the new method is also capable to identify and distinguish both species of licorice. The quantitative HPTLC results were in accordance with the data obtained by high-performance liquid chromatography (HPLC) following the United States Pharmacopeia (USP) method on licorice root. In addition, we used two DNA candidate barcodes (internal transcribed spacer [ITS] and psbA-trnH intergenic spacer) for species identification.