Application of Taxonomic and Dna Barcoding Techniques in Identifying Commonly Traded Herbal Plant Species in Selected Counties, Kenya

Abstract

Over eighty percent of the world’s population depends on herbal products for their basic health care needs. However, this widespread popularity is counterbalanced with the lack of relevant research to authenticate the source and purity of the traditional herbal products. There exists an extensive history on use of herbal products but lately there are concerns on authenticity and safety of these products. The objectives of the study were: determine plant species commonly traded as herbal products, assess the products using taxonomic and DNA barcoding techniques, application of DNA barcoding technology in reference barcodes generation, and determine if the plant herbal products are accurately labeled. The study was carried out in selected markets in three counties in Kenya (Kajiado, Narok and Nairobi). Data collection involved use of structured questionnaires, species observation, taxonomic and DNA barcoding techniques. Structured questionnaires were administered to individual herbalists and complementary interviews with key herbalists to enrich the data collected. The local and common names were recorded and later translated to scientific names using para-taxonomists and previously published data. Scientific names listed on labels of packaged plants products were as well recorded. The generated species list guided the collection of voucher specimens and creation of a reference library of DNA barcodes. DNA barcoding technology was used to authenticate the herbal product samples. The common single species samples were analyzed using Internal Transcribed Spacer (ITS) and ribulose -1,5-bisphosphate carboxylase Large subunit (rbcL) DNA barcoding markers while metabarcoding was applied in multi-species samples using nrITS2 marker. The study revealed that 86 plant species belonging to 43 families were traded as herbal products in the regions. Most of these plants were shrubs (66 %) traded as stem and bark. Majority of herbal plant species belong to Fabaceae, Apocynaceae and Rhamnaceae families. The DNA technology successfully generated barcode sequences that were used as reference for herbal products identification. Single species samples were found to be more authentic compared to the mixed species samples as most species were identified to species level as listed on the label. Adulteration in single species samples was mainly by substitution with closely related and/or looks alike species, which raises concern on value and quality of the herbal products sold in the studied counties. Kajiado County had more authentic samples in comparison to Narok and Nairobi. DNA metabarcoding technology was successful in identification of mixed species sample at 92 % to species level and 4 % each to genus and family level. This study has made the first attempt to identify herbal plant species traded in selected markets in Kenya using DNA barcoding technology in combination with morphological and literature methods. Authentication using DNAbarcoding provided a more reliable and accurate results compared to morphological identification. DNA barcoding should therefore be applied in identification and verification of herbal products. DNA barcodes successfully generated and deposited in National Centre for Biotechnology Information (NCBI) Genbank form crucial reference data for future studies and can be used as a baseline library for useful medicinal plants of Kenya.