Impact of Species, Growth Conditions, and Plant Processing on the Phytochemistry and Antimicrobial Activity of <i>Agrimonia</i> Extracts

Agrimonia eupatoria L., a herb used in traditional medicine, contains numerous secondary metabolites with beneficial properties. However, its phytochemistry, and consequently bioactivity, can be strongly influenced by various cultivation and processing factors. This study evaluates the impact of growth locality, plant part, ontogenetic phase, and postharvest processing on the phytochemical composition and antimicrobial potential of two agrimony species: A. eupatoria and Agrimonia procera. A total of 94 herbal samples extracted with 40% aqueous ethanol were analyzed using ultrahigh-performance liquid chromatography and high-resolution tandem mass spectrometry and simultaneously tested against selected Gram-positive, Gram-negative, and anaerobic bacteria and yeasts. Targeted screening of bioactive polyphenols revealed significant differences between the agrimony species, with phloridzin and orientin/isoorientin identified as new potential chemotaxonomic markers. Notable differences were also observed between roots and aerial parts. Postharvest processing, particularly drying, proved to be another important factor, reducing the overall polyphenol content compared to fresh-frozen plant material. Although all extracts exhibited strong activity, especially against Gram-positive bacteria, the highest antimicrobial potential was observed in roots extracts rich in procyanidins and catechins. The findings of this study enhance the understanding of agrimony phytochemistry and its variability, thereby supporting the effective production of medicinal preparations with the desired therapeutic effects.