Background/Objectives: This study aimed to develop gel nanoemulsions (NEs) of Brazilian essential oils (EOs) from Eugenia uniflora and Psidium guajava, as well as to perform chemical characterization and investigate the antimicrobial activity of the EOs and NEs. Results/Conclusions: The main chemical compounds of E. uniflora EO were curzerene (34.80%) and germacrene B (11.92%), while those of P. guajava EO were β-caryophyllene (25.92%), β-selinene (22.64%), and γ-selinene (19.13%). The NEs of E. uniflora and P. guajava had droplet sizes of 105.30 and 99.50 nm and polydispersity index (PDI) values of 0.32 and 0.43, respectively. The NEs remained stable for 30 days of storage at 25 °C, with droplet sizes of 104.7 and 103.8 nm, PDI values below 0.50, and no phase separation. The NE of E. uniflora exhibited inhibition zones ranging from 8.41 to 15.13 mm against the Gram-positive bacterium Staphylococcus aureus and the Gram-negative bacteria Pseudomonas aeruginosa, Klebsiella pneumoniae, and Acinetobacter baumannii. Additionally, the NE of E. uniflora showed the largest inhibition zones against Candida albicans (20.97 mm) and Candida krusei (15.20 mm), along with low minimum inhibitory concentration (MIC) values (0.54–1.22 mg/mL) and minimal bactericidal concentration (MBC) values (4.84–11.02 mg/mL) against these pathogenic yeasts. The NE of P. guajava demonstrated low MIC (1.26 mg/mL) and MBC (11.35 mg/mL) values for C. krusei. The time–growth inhibition assay also suggests the effectiveness of the NE against the tested pathogens S. aureus and E. coli, highlighting its potential as a novel alternative therapeutic agent.

The aim of this study was to evaluate the antibacterial activity of nanoemulsions of Baccharis dracunculifolia essential oil. The volatile compounds of the essential oil were identified using gas chromatography–mass spectrometry. The properties of the nanoemulsions (droplet size, polydispersity index, pH, and electrical conductivity) were determined. The antibacterial activities of the essential oil and its nanoemulsions were evaluated using MIC, MBC, and disk diffusion. The microorganisms used were: Gram-positive bacteria (Staphylococcus aureus ATCC 25923, Bacillus cereus ATCC 14579, Streptococcus mutans ATCC 25175, and Enterococcus faecalis ATCC 29212) and Gram-negative bacteria (Pseudomonas aeruginosa ATCC 27853, Klebsiella pneumoniae ATCC BAA-1706, Salmonella enterica ATCC 14028, and Escherichia coli ATCC 25922). The major volatile compounds of the B. dracunculifolia essential oil were limonene (19.36%), (E)-nerolidol (12.75%), bicyclogermacrene (10.76%), and β-pinene (9.60%). The nanoemulsions had a mean droplet size between 13.14 and 56.84 nm. The nanoemulsions presented lower and statistically significant MIC values compared to the essential oil, indicating enhancement of the bacteriostatic action. The disk diffusion method showed that both the nanoemulsions and the essential oil presented inhibition zones only for Gram-positive bacteria, while there were no results against Gram-negative bacteria, indicating that B. dracunculifolia essential oil has a better antimicrobial effect on Gram-positive microorganisms.

Background/Objectives: This study aimed to evaluate the chemical composition and antimicrobial activity of Cordia verbenacea essential oil (EOCV) and to develop and characterize a gel-based nanoemulsion of C. verbenacea essential oil (NECV). Methods: The EOCV was chemically characterized by gas chromatography (GC-FID and GC-MS). The nanoemulsion was prepared using EOCV, the surfactants Cremophor and Plurol Oleique, and phosphate buffer at pH 5.5, and was subjected to experiments to determine its stability, irritant potential and in vitro skin permeation. Results: The main chemical compounds identified in EOCV were α-pinene (33.05%) and β-caryophyllene (25.11%). The EOCV exhibited antimicrobial activity with MIC and MBC values ranging from 6.3 to 25.0 µL/mL for the yeasts Candida albicans and C. krusei, 11.3 to 25.0 µL/mL for the Gram-positive bacteria Bacillus cereus, Staphylococcus aureus, and Enterococcus faecalis, and 12.5 to 75.0 µL/mL for the Gram-negative bacteria Acinetobacter baumannii, Klebsiella pneumoniae, and Escherichia coli. The NECV showed a droplet size of 126.80 nm, a polydispersity index (PDI) of 0.49, a zeta potential of −18.50 mV and a pH of 5.3 and remained stable for 60 days of storage at 25 °C and 4 °C. The HET-CAM irritation test showed that the formulation is non-irritating. The in vitro skin permeation assay showed that the NECV penetrated the deeper layers of the skin, demonstrating its ability to overcome the Stratum corneum barrier. Conclusions: These results are highly promising regarding the potential use of NECV for topical application for the treatment of infected skin wounds.