Antimicrobial assays of three native British plants used in Anglo-Saxon medicine for wound healing formulations in 10th century England

Ethnopharmacological relevance: Three important Anglo-Saxon medical texts from the 10th century contain herbal formulations for over 250 plant species, many of which have yet to be evaluated for their phytochemical and/or pharmacological properties. In this study, three native British plants were selected to determine antimicrobial activity relevant to treating bacterial infections and wounds.
Materials and methods: Several preparations of Agrimonia eupatoria L., Arctium minus (Hill) Bernh. and Potentilla reptans L. were screened for antimicrobial activity against selected Gram-positive and Gram-negative bacteria of relevance in wounds using a 96 well plate microdilution method (200, 40 and 8 µg/mL). Minimum inhibitory concentration (MIC) values were determined for the most potent extracts from 2-0.004 mg/mL and HPLC chromatograms examined by multivariate analysis. Principle components analysis (PCA) was used to identify chemical differences between antimicrobial activity of the crude extracts.
Results: The HPLC-PCA score plots attributed HPLC peaks to the antimicrobial activity with all three plants inhibiting growth of Gram-positive Staphylococcus aureus by >50% in four or more extracts. The first two principal components (PC) represented 87% of the dataset variance. The P. reptans 75% ethanol root extract exhibited the greatest range of activity with MIC50 at 31.25 µg/mL to a total MIC that was also the minimum bactericidal concentration (MBC) at 1 mg/mL. Additionally, the root of P. reptans inhibited growth of Gram-negative bacteria with the 75% ethanol extract having a MIC50 at 1 mg/mL against Pseudomonas aeruginosa and the decoction a MIC50 at 3.9 µg/mL against Escherichia coli.

Conclusions: The results indicate a moderate antimicrobial activity against common wound pathogens for P.reptans suggesting it may well have been effective for treating wound and bacterial infections. Anglo-Saxon literary heritage may provide a credible basis for researching new antimicrobial formulations. Our approach encompassing advanced analytical technologies and chemometric models paves the way for systematic investigation of Anglo-Saxon medical literature for further therapeutic indications to uncover knowledge of native British plants, some of which are currently lost to modern Western herbal medicine.