Development and Validation of an Analytical Framework for Detecting Adulteration in High-Value Nigerian Herbal Medicines Using DNA Barcoding and Metabolomics

Herbal medicine adulteration poses serious public health risks and is a pervasive challenge in Nigerian herbal markets, where economic incentives and inadequate regulatory capacity facilitate the substitution of authentic high-value medicinal species with morphologically similar but pharmacologically inactive or toxic materials. This research develops and validates an integrated analytical framework combining DNA barcoding and untargeted metabolomics for the definitive identification and adulteration detection of five high-value Nigerian medicinal species: Garcinia kola, Monodora myristica, Cryptolepis sanguinolenta, Rauwolfia vomitoria, and Fagara zanthoxyloides. DNA barcoding utilised the rbcL, matK, and ITS2 loci with primers and protocols optimised for processed and degraded herbal materials. Reference sequences were deposited in a curated Nigerian Medicinal Plant DNA Barcode Library. Metabolomic fingerprinting was performed by UHPLC-QTOF-MS with GNPS molecular networking and supervised OPLS-DA modelling using 120 authenticated versus suspect market samples. The combined framework achieved 97.4% species identification accuracy, compared to 81.2% for morphological authentication alone. Adulteration was detected in 34% of market samples across all five species. Four adulterant species were identified, two of which carry documented hepatotoxic alkaloids. The framework was validated for repeatability, reproducibility, and false positive/negative rates and is proposed for adoption by NAFDAC as a rapid quality assurance protocol for Nigerian herbal product certification. Keywords: DNA barcoding, metabolomics, adulteration, Nigerian herbal medicines, NAFDAC