Phenolic composition and antimicrobial activity of semi-arid Chilean propolis against human and plant pathogens associated with fresh produce

Propolis is a natural resin produced by honeybees, characterized by a complex composition of bioactive compounds with antimicrobial activity. This study evaluated ethanolic extracts of propolis from the semi-arid Coquimbo Region (Chile), focusing on their chemical composition and antimicrobial activity against foodborne bacteria and postharvest fungal pathogens. Botanical analysis confirmed a diverse plant origin, with contributions from native species such as Escallonia pulverulenta and Baccharis concava. Chemical characterization showed marked variability among samples, with high total phenolic content and distinct phenolic profiles, including compounds such as p-coumaric acid and pinocembrin. Extracts exhibited greater antibacterial activity against Listeria monocytogenes and Staphylococcus aureus than against Escherichia coli and Salmonella enterica, and also inhibited the growth of Alternaria alternata and Botrytis cinerea. Assays on lettuce and tomato tissues demonstrated rapid reductions in surface-associated populations of L. monocytogenes and S. aureus, although internalized cells were less affected. Fungal disease severity was also reduced in plant tissues, with some treatments showing effects comparable to commercial fungicide under the conditions tested. One extract also contributed to preserving tomato tissue integrity during storage. Overall, the observed differences among extracts suggest that antimicrobial activity may depend not only on total phenolic content but also on specific phenolic profiles and potentially synergistic interactions among extract constituents. These findings support the potential of semi-arid Chilean propolis as a natural antimicrobial candidate for improving fresh produce preservation, while highlighting the need for further studies with broader sampling and application-oriented validation.