A post-antibiotic era looms: can plant natural product research fill the void?

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).