Using DNA markers and barcoding to solve the common problem of identifying dried medicinal plants with the examples of Smilax and Cissus in Thailand

Abstract

Medicinal herbs called Khao-Yen Nuer and Khao-Yen Tai in Thai traditional medicines have been used as common ingredients in several preparations. They were claimed to be Smilax china or Smilax glabra. In order to identify the dried medicines, fresh samples of S. chinaand S. glabra were collected. Another two fresh samples with the same local names were also collected from Chiang Mai province, and were later morphologically identified asCissus repens. These samples served as reference standards for the other dried samples. Nine dried samples of the two herbs were randomly collected from pharmacies in the provinces of Thailand. DNA barcodes by trnH-psbA spacer region show great variations in banding sizes as DNA markers and genetic distances (D) from sequences. The D values in same, and different species ranged from 0 to 12.9%, and 23.2 to 32.3%, respectively. Based on the D values, four dried samples were identified as S. china and S. glabra while the other five dried samples are of the same unknown species and are used as Khao-Yen Nuer and Khao-Yen Tai in different provinces and parts of Thailand. The trnH-psbA spacer region is an efficient barcode and marker identifying the studied plant group.  Aside from reaching success in the research aims, the results have led us to an accidental discovery. One of the more important practices of traditional healers is to use C. repens and other unknown plant alternatives with S. china or S. glabra to create the traditional medicine called Khao-Yen Nuer and Khao-Yen Tai.   Key words: Cissus repens, DNA barcode, medicinal plant discovery, Smilax china, Smilax glabra, trnH-psbA