DNA barcoding aids in identification of adulterants of Trillium govanianum Wall. ex D. Don

Abstract

The correct scientific identification of the plant material is crucial to the safety and efficacy of herbal products. Trillium govanianum Wall. ex D. Don, a pharmaceutically prized medicinal plant species endemic to the Himalaya, has been recently subjected to large-scale extraction in the wild due to increasing market demand. Consequently, adulteration and/or substitution of the traded material of T. govanianum with closely-related plants such as Paris polyphylla Sm. has become a quality control problem for the herbal industry. Therefore the present study aimed to (i) develop a reference DNA barcode of T. govanianum and its potent adulterant P. polyphylla for correct identification, (ii) and check adulteration of market samples of T. govanianum. Reference DNA barcode library of T. govanianum and P. polyphylla was successfully established, using Internal transcribed spacer (ITS), Maturase K (matK), chloroplast intergenic spacer (trnH-psbA), and ribulose-bisphosphate carboxylase (rbcL) regions. The ITS, matK and trnH-psbA were found to be ideal reference barcodes for T. govanianum, while ITS and trnH-psbA were suitable for P. polyphylla. All the trade samples (i.e. dried rhizomes), investigated during the present study, got putatively identified with the respective reference barcodes; and thereby indicating the ITS and trnH-psbA regions as the potential DNA barcodes for the identification of the trade samples/adulterants. The ITS region showed the highest mean intra- and inter-specific distances, which proves its high efficiency in differentiating closely related species. Phylogenetic trees were also constructed following the neighbor-joining (NJ) method, based on ITS, rbcL, and trnH-PsbA regions of Trillium and Paris species, which distinguished Trillium species from those of Paris. The availability of a novel DNA barcode for this important medicinal plant species will be helpful for correct identification of its raw plant material, checking illegal trade, and to regulate its sustainable collection from the natural habitats.