Antimicrobial resistance is increasing among certain pathogenic bacteria to the extent that treatment efficacy is no longer always assured. According to the CDC, as few as six new antibiotics have been released for use over the past 30 years. Resistance has already been observed to each of these. Eleven plant natural products have been approved for therapeutic use during the same period--none of them being antimicrobial agents. We have learned through experience that some microorganisms will inevitably overcome antibiotic treatment in certain situations, and then spread. It is clear that the rate of new antimicrobial development is insufficient to meet our current and future needs, which should be addressed in order to guarantee the effective future of antimicrobial chemotherapy. However, in recent years there has been an increase in the number of peer-reviewed reports of antimicrobial efficacy among plant-derived secondary metabolites. A limitation with these reports is the wide range of modified in vitro methods used to determine antimicrobial efficacy of these products, showing an absence of the type of standardisation that is the norm when testing the efficacy of single- or combined-agent conventional antimicrobials in the laboratory, thereby making inter-study comparison difficult. Overall, despite the large diversity in preparation and testing strategies used currently for natural product plant-derived antimicrobials, our investigations suggest that the field shows promise in the provision of novel antimicrobial agents, even as exemplified by our selected example, Inula helenium (Elecampane).

With antimicrobial resistance rising globally, the exploration of alternative sources of candidate molecules is critical to safeguard effective chemotherapeutics worldwide. Plant natural products are accessible, structurally diverse compounds with antimicrobial potential. The pharmacological applications of plants in medicine can be guided by the attestation of traditional use, as demonstrated in this study. In Irish ethnomedical literature, Inula helenium L. (elecampane) is often indicated for respiratory and dermal ailments. This is the first assessment of antimicrobial sesquiterpene lactones from the roots of elecampane, naturalised in Ireland. Traditional hydro-ethanolic extracts were prepared from multi-origin elecampane roots. A novel clean-up strategy facilitated the bioactivity-guided fractionation of a subset of anti-staphylococcal fractions (the compositions of which were investigated using HPLC-DAD, supported by 1H NMR). The natural products attributing to the antimicrobial activity, observed in vitro, were identified as alantolactone (1), isoalantolactone (2), igalan (3), and an unseparated mixture of dugesialactone (4) and alloalantolactone (5), as major compounds. The findings suggest that the geographical origin of the plant does not influence the anti-bacterial potency nor the chemical composition of traditional elecampane root. Considering the prevalence of staphylococci-associated infections and associated broad spectrum resistance in Irish hospitals, currently, further research is warranted into the usage of the identified compounds as potential candidates in the control of staphylococcal carriage and infection.

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Knowledge of element concentrations in botanical extracts is relevant to assure consumer protection given the increased interest in plant-based ingredients. This study demonstrates successful multi-element investigations in order to address the lack of comprehensive profiling data for botanical extracts, while reporting for the first time the metallomic profile(s) of arnica, bush vetch, sweet cicely, yellow rattle, bogbean, rock-tea and tufted catchfly. Key element compositions were quantified using a validated HR-ICP-SFMS method (µg kg−1) and were found highly variable between the different plants: Lithium (18–3964); Beryllium (3–121); Molybdenum (75–4505); Cadmium (5–325); Tin (6–165); Barium (747–4646); Platinum (2–33); Mercury (5–30); Thallium (3–91); Lead (12–4248); Bismuth (2–30); Titanium (131–5827); Vanadium (15–1758); Chromium (100–4534); Cobalt (21–652); Nickel (230–6060) and Copper (1910–6340). Compendial permissible limits were not exceeded. Overall, no evidence of a health risk to consumers could be determined from consumption of the investigated plants at reasonable intake rates. Mathematical risk modelling (EDI, CDI, HQ, HI) estimated levels above safe oral thresholds only for Cd (16%) and Pb (8%) from higher intakes of the respective plant-derived material. Following high consumption of certain plants, 42% of the samples were categorised as potentially unsafe due to cumulative exposure to Cu, Cd, Hg and Pb. PCA suggested a potential influence of post-harvest processing on Cr, Ti and V levels in commercially-acquired plant material compared to wild-collected and farm-grown plants. Moreover, a strong correlation was observed between Pb-Bi, Be-V, Bi-Sn, and Tl-Mo occurrence. This study may support future research by providing both robust methodology and accompanying reference profile(s) suitable for the quality evaluation of essential elements and/or metal contaminants in botanical ingredients.