Species identification and quality evaluation of licorice in the herbal trade using DNA barcoding, HPLC and colorimetry

Abstract

Licorice is a product with the same origin as medicine and food and is widely used in traditional Chinese medicine and the food, cosmetics and tobacco industries. With the increasing demand for licorice in the herbal market, there is also increasing concern about complex varieties and quality deterioration. Considering the importance of the quality and safety of commercial licorice products, we used DNA barcoding, HPLC and colorimetry to distinguish and evaluate commercial licorice products. Here, 52 samples could be accurately identified into three kinds of licorice, Glycyrrhiza uralensis Fisch. (Gu), Glycyrrhiza inflata Bat. (Gi) and Glycyrrhiza glabra L. (Gg), by internal transcribed spacer (ITS) and trnH-psbA sequences. Among them, the S27 sample was identified as Gi but had been incorrectly labeled as Gg. Based on HPLC combined with stoichiometric analysis, the contents of liquiritin, glycyrrhizic acid and isoliquiritin contents were significantly different between Gu and Gg, and Gi and Gg showed significant differences only in isoliquiritigenin content. The chemical components and color difference parameters showed that isoliquiritigenin had a significant correlation with the color parameter b*. The above results show that DNA barcoding can quickly and accurately distinguish species, but it cannot provide data on metabolites or other quality information beyond the plant raw materials. Techniques that combine of DNA barcoding, HPLC and colorimetry can more easily distinguish and evaluate the types and quality of commercial licorice products. This study provides good data support for the safety and quality of licorice in the Chinese market.