[The molecular identification of licorice species and the quality evaluation of licorice slices]

Abstract

Licorice is one of the most common herbs in traditional Chinese medicine, and classified as top grade in Shen Nong Ben Cao Jing. There are three different original plants of licorice stipulated in Chinese Pharmacopeia, Glycyrrhiza uralensis Fisch., Glycyrrhiza glabra L., and Glycyrrhiza inflata Bat. However, previous investigation showed that the pharmacodynamic effects of the three licorices were quite different. It is very difficult to identify them by the classical identification methods. In order to establish a fast and effective identification method, we collected 240 licorice plants from 21 populations of 7 provinces, and amplified their ITS and psbA-trnH sequences. ITS sequences with a full length of 616 bp and psbA-trnH sequences with a full length of 389 bp were obtained separately. Using DNAMAN to analyze these sequences, 4 variable sites were found in ITS sequences and 2 ITS haplotypes were determined, and 3 variable sites were found in psbA-trnH sequences and 4 psbA-trnH haplotypes were determined. With the combination analysis of ITS and psbA-trnH sequences, the molecular identification method of original licorice was established. Using this method, 40 samples of licorice slices collected from 4 main herbal material markets in China were identified successfully. Furthermore, the contents of 2 triterpenes, 18α-glycyrrhizic acid and 18β-glycyrrhizic acid, and 4 flavonoids, liquiritin, isoliquiritin, liquiritigenin, and isoliquiritigenin in these licorice pieces were examined by HPLC and the results were analyzed using SPSS 21.0. This study provides a new method in identification of licorice, which may serve as a guideline for quality control of licorice slices.