Abstract

BackgroundWhile DNA barcoding is an important technology for the authentication of the botanical origins of Chinese medicines, the suitable markers for DNA barcoding of the genus Uncaria have not been reported yet. This study aims to determine suitable markers for DNA barcoding of the genus Uncaria (Gouteng).MethodsGenomic DNA was extracted from the freshly dried leaves of Uncaria plants by a Bioteke’s Plant Genomic DNA Extraction Kit. Five candidate DNA barcode sites (ITS2, rbcL, psbA–trnH, ITS, and matK) were amplified by PCR with established primers. The purified PCR products were bidirectionally sequenced with appropriate amplification primers in an ABI-PRISM3730 instrument. The candidate DNA barcodes of 257 accessions of Uncaria in GenBank were aligned by ClustalW. Sequence assembly and consensus sequence generation were performed with CodonCode Aligner 3.7.1. The identification efficiency of the candidate DNA barcodes was evaluated with BLAST and nearest distance methods. The interspecific divergence and intraspecific variation were assessed by the Kimura 2-Parameter model. Genetic distances were computed with Molecular Evolutionary Genetics Analysis 6.0.ResultsThe accessions of the five candidate DNA barcodes from 11 of 12 species of Uncaria in China and four species from other countries were included in the analysis, while 54 of total accessions were submitted to GenBank. In a comparison of the interspecific genetic distances of the five candidate barcodes, psbA–trnH exhibited the highest interspecific divergence based on interspecific distance, theta prime, and minimum interspecific distance, followed by ITS2. The distribution of the interspecific distance of ITS2 and psbA–trnH was higher than the corresponding intraspecific distance. Additionally, psbA–trnH showed 95.9 % identification efficiency by both the BLAST and nearest distance methods regardless of species or genus level. ITS2 exhibited 92.2 % identification efficiency by the nearest distance method, but 87 % by the BLAST method.ConclusionWhile psbA–trnH and ITS2 (used alone) were applicable barcodes for species authentication of Uncaria, psbA–trnH was a more suitable barcode for authentication of Uncaria macrophylla.Electronic supplementary materialThe online version of this article (doi:10.1186/s13020-015-0072-7) contains supplementary material, which is available to authorized users.

Highlights

  • While DNA barcoding is an important technology for the authentication of the botanical origins of Chi‐ nese medicines, the suitable markers for DNA barcoding of the genus Uncaria have not been reported yet

  • This study aims to determine suitable markers for DNA barcoding of the genus Uncaria

  • Plant materials Fifty-four sequences from our laboratory, among which 12 samples of six species of Uncaria (U. rhynchophylla, U. macrophylla, U. sessilifructus, U. hirsuta, U. lancifolia and U. homomalla) are used as Gouteng in Chinese medicine (CM) markets, were collected from areas in Guangxi Province, including Rongshui, Sanjiang, Shanglin, Ningming, and Jinxi county, Nanning Sitang town, and Guangxi Medicinal Botanical Garden, in 2009 and 2010 by Professor Ruisong Huang

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Summary

Introduction

While DNA barcoding is an important technology for the authentication of the botanical origins of Chi‐ nese medicines, the suitable markers for DNA barcoding of the genus Uncaria have not been reported yet. Adulterants of Gouteng include Uncaria laevigata, Uncaria lancifolia, Uncaria scandens, Uncaria rhynchophylloides, and Uncaria homomalla [7, 9], due to similar organoleptic characteristics to those of U. rhynchophylla. Several DNA regions, such as ITS2, psbA–trnH, matK, rbcL, ITS, ycf, and rpoC1 [14, 18,19,20,21] have been evaluated as potential DNA barcodes in medicinal plants Among these candidate barcoding loci, the ITS2 locus had the highest identification efficiency among all tested regions, and discriminated a wide range of plant taxa [14, 22]. The psbA–trnH intergenic region was a suitable DNA marker for identification of flowering plants [17, 18], pteridophytes [24], Lonicera japonica Thunb from Caprifoliaceae [21], and aquatic plant species [25]

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