RESUMEN
ETHNOPHARMACOLOGICAL RELEVANCE: Antimicrobial drug resistance is a growing threat to global public health. Historical records and herbal texts relating to traditional Celtic medicine indicate an extensive pharmacopeia of plants for treating infections likely caused by microbes. However, a major barrier for successful integration of these remedies into mainstream practice is the current lack of accurate interpretation and scientific validation. MATERIALS AND METHODS: We investigated the flora of the Isle of Arran, Scotland, via in situ targeted screening of 83 out of 138 plants identified in Meddygion Myddvai (a 14th century Welsh manuscript) to treat conditions related to microbial infections, and an additional 18 plants from modern ethnobotanical knowledge on the island (Scottish School of Herbal Medicine). In a follow-up proof-of-concept study, bioassay-guided fractionation was performed to identify bioactive constituents from two high scoring hits that inhibited Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative) bacterial growth. RESULTS: 67 historical plants (80.7%) and 14 modern plants (77.8%) were found to have detectable levels of antimicrobial activity when tested using Mobile Discovery kits, with human saliva as a source of bacteria for screening. Sabinene, a natural bicyclic monoterpene from juniper "berries" (Juniperus communis L.) and alliin, a natural sulfoxide from garlic cloves (Allium sativum L.), were isolated and confirmed as primary antibacterial leads. CONCLUSION: Using historical medical sources such as those associated with traditional Celtic medicine to guide rigorous, evidence-based scientific investigation, provides additional leads for new and alternative bioactive molecules for combating bacterial diseases.