DNA barcoding augments conventional methods for identification of medicinal plant species traded at Tanzanian markets

Sarina Veldman; Yingzi Ju; Joseph N Otieno; Siri Abihudi; Chantal Posthouwer; Barbara Gravendeel; Tinde R van Andel; Hugo J de Boer

doi:10.1016/j.jep.2019.112495

DNA barcoding augments conventional methods for identification of medicinal plant species traded at Tanzanian markets

J Ethnopharmacol. 2020 Mar 25:250:112495. doi: 10.1016/j.jep.2019.112495. Epub 2019 Dec 23.

Authors

Sarina Veldman¹, Yingzi Ju², Joseph N Otieno³, Siri Abihudi⁴, Chantal Posthouwer⁵, Barbara Gravendeel⁶, Tinde R van Andel⁵, Hugo J de Boer⁷

Affiliations

¹ Department of Systematic Biology, Evolutionary Biology Center, Uppsala University, Norbyvägen 18D, SE-75236, Uppsala, Sweden; Naturalis Biodiversity Center, P.O. Box 9517, 2300 RA, Leiden, the Netherlands. Electronic address: sarina.veldman@naturalis.nl.
² Department of Systematic Biology, Evolutionary Biology Center, Uppsala University, Norbyvägen 18D, SE-75236, Uppsala, Sweden.
³ Institute of Traditional Medicine Muhimbili University of Health and Allied Sciences, P.O.Box 65001, Dar es Salaam, Tanzania.
⁴ Institute of Traditional Medicine Muhimbili University of Health and Allied Sciences, P.O.Box 65001, Dar es Salaam, Tanzania; Nelson Mandela African Institution for Science and Technology (NM-AIST), P.O. Box 447, Arusha, Tanzania.
⁵ Naturalis Biodiversity Center, P.O. Box 9517, 2300 RA, Leiden, the Netherlands.
⁶ Naturalis Biodiversity Center, P.O. Box 9517, 2300 RA, Leiden, the Netherlands; University of Applied Sciences Leiden, Leiden, the Netherlands.
⁷ Department of Systematic Biology, Evolutionary Biology Center, Uppsala University, Norbyvägen 18D, SE-75236, Uppsala, Sweden; Naturalis Biodiversity Center, P.O. Box 9517, 2300 RA, Leiden, the Netherlands; Natural History Museum, University of Oslo, Norway.

PMID: 31877364
DOI: 10.1016/j.jep.2019.112495

Abstract

Ethnopharmalogical relevance: In Africa, traditional medicine is important for local healthcare and plants used for these purposes are commonly traded. Identifying medicinal plants sold on markets is challenging, as leaves, barks and roots are often fragmented or powdered. Vernacular names are often homonymic, and identification of material lacking sufficient morphological characters is time-consuming, season-dependent and might lead to incorrect assessments of commercialised species diversity.

Aim of the study: In this study, we identified cases of vernacular heterogeneity of medicinal plants using a tiered approach of literature research, morphology and DNA barcoding.

Material and methods: A total of 870 single ingredient medicinal plant samples corresponding to 452 local names were purchased from herbal markets in Dar-es-Salaam and Tanga, Tanzania, and identified using conventional methods as well as DNA barcoding using rbcL, matK and nrITS.

Results: Using conventional methods, we could identify 70% of samples to at least family level, while 62% yielded a DNA barcode for at least one of the three markers. Combining conventional methods and DNA barcoding, 76% of the samples could be identified to species level, revealing a diversity of at least 175 species in 65 plant families. Analysis of the market samples revealed 80 cases of multilingualism and over- and under-differentiation. Afzelia quanzensis Welw., Zanthoxylum spp., Allophylus spp. and Albizia anthelmintica Brongn. were the most evident cases of multilingualism and over-differentiation, as they were traded under 8-12 vernacular names in up to five local languages. The most obvious case of under-differentiation was mwingajini (Swahili), which matched to eight scientific species in five different plant families.

Conclusions: Use of a tiered approach increases the identification success of medicinal plants sold in local market and corroborates findings that DNA barcoding can elucidate the identity of material that is unidentifiable based on morphology and literature as well as verify or disqualify these identifications. Results of this study can be used as a basis for quantitative market surveys of fragmented herbal medicine and to investigate conservation issues associated with this trade.

Keywords: DNA barcoding; Herbal medicine; Tanzania; Trade; Vernacular names.

MeSH terms

DNA Barcoding, Taxonomic*
Medicine, African Traditional*
Plants, Medicinal / classification*
Plants, Medicinal / genetics
Tanzania