Interactions in medicinal plant-based antimicrobials: synergy, antagonism and all that goes in between

The antimicrobial properties of medicinal plants are not only influenced by their individual activities but also by the intricate interactions. These interactions, including synergy, antagonism, and what goes in between are pivotal in understanding antimicrobial efficacy in combined blends. This study aims to explore the various types of antimicrobial interactions providing examples from our studies focusing on several interaction types: (1) Compound combinations between South African propolis compounds flavonoids pinocembrin, galangin, and chrysin which demonstrate synergy, while exhibiting reduced toxicity in combination (2) Blends used in aromatherapy, where more than 1500 essential oil combinations were analysed and an intricate analysis of synergistic, antagonistic, additive and non-interactive interactions are reported. Results demonstrate the value of using carrier oils for an enhanced antimicrobial effect, as well as reducing toxicity (3) Enantiomeric effects, using the model compound limonene where the combination with other essential oil compounds demonstrate variable interactions depending on the racemate studied (4) African traditional healing using the example of Lippia javanica in combination with other medicinal plants against respiratory pathogens (5) Plant combinations with the biome where plants used to treat gastric ulcers have been explored and their interactions with the gut microbiome demonstrate selective synergy, and lastly, (6) Combinations with conventional antibiotics where we explored the effects of traditionally used medicinal plants collected from Muthi markets with antibiotics. The prevalent antagonism found was alarming ([ Fig. 1 ]). Fig. 1 Oral presentation plan This research highlights the need for a multidimensional approach to studying medicinal plant combinations. It opens new avenues for developing novel, effective, and sustainable antimicrobial therapies, particularly in the context of global antimicrobial resistance. Publication History Article published online: 05 March 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany