Evaluation of the Antibacterial and Antifungal Capacity of Nanoemulsions Loaded with Synthetic Chalcone Derivatives Di-Benzyl Cinnamaldehyde and Benzyl 4-Aminochalcone

With the increase in antimicrobial resistance, it has become necessary to explore alternative approaches for combating and preventing diseases. DB-cinnamaldehyde (CNM) and Benzyl4-amino (B4AM) are bioactive compounds derived from chalcones but with restricted solubility in aqueous media. Nanoemulsions can enhance the solubility of compounds and can be a promising alternative in the development of novel antimicrobials, with reduced side effects and prolonged release. The objective of this study was to evaluate the stability of oil-in-water nanoemulsions loaded with two distinct types of chalcones at two different dosages, to propose a stable formulation with antimicrobial properties. Results showed that nanoemulsions presented high encapsulation efficiency, low polydispersity index (PDI) and particle size below 200 nm, indicating that emulsification was a suitable method for nanoemulsion preparation. Nanoemulsions with higher dosages exhibited significant antimicrobial effects when compared to free chalcones and positive controls. Notably, B4AM nanoemulsions at higher dosages showed expressive activity against Salmonella minnesota, with a 420% greater inhibitory response compared to the free form and showing equivalence to the positive control. CNM nanoemulsions showed excellent inhibitory activity at the highest dosage, equivalent to the positive control against S. minnesota and Staphylococcus aureus. The greater number of conjugated bonds in CNM increased the antimicrobial activity in comparison with B4AM, and the formation of nanometric domains enhanced the bioavailability, being a promising alternative for antimicrobial applications.