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.

This study evaluated the influence of tea, sucrose, and inoculum concentrations on green tea kombucha’s physicochemical properties and antioxidant capacity to optimize its production. The highest total phenolic content (98.61 mg GAE/100 mL) and radical scavenging activity for ABTS (9647.14 μmol/mL) and DPPH (6640.00 μmol/mL) were observed with 8 g/L of tea, 80 g/L of sucrose, and 30% inoculum. Principal Component Analysis highlighted inoculum as the key factor influencing these parameters. Following this, fermentation was scaled up in 6.5 L bioreactors operating under static and stirred conditions. Monitoring physicochemical properties, antioxidant capacity, and volatile compounds revealed the impact of agitation on fermentation, with the kombucha obtained by static cultivation presenting higher biological activity. Eleven volatile compounds were identified, including carboxylic acids, terpenes, esters, alcohols, and phenols. Notably, α-terpinolene, dodecanoic acid, and 2,4-di-tert-butylphenol, found in kombucha, exhibit antioxidant properties linked to health benefits. Differences in volatile compound profiles were observed between static and stirred processes. This study concluded that kombucha maintains its physicochemical characteristics and bioactivity during scale-up, contributing to a better understanding of large-scale production. It also suggests stirred cultivation as an alternative for kombucha production.

In the laboratory, were evaluated the effects (residual contact and feeding deterrence) of the essential oils from the leaves of Piper aduncum, Lippia sidoides and Schinus terebinthifolius, as well as eleven selected constituents and binary blends of oils in different proportions against 3rd instar larvae of Plutella xylostella (L.). The Piper oil demonstrated the greatest toxicity (LC50 = 0.31 µL/mL) and feeding deterrence (DC50 = 1.08 µL/mL) between oils tested. Dillapiole (LC50 = 1.01 µL/mL; DC50 = 1.10 µL/mL) and carvacrol (LC50 = 6.03 µL/mL; DC50 = 0.075 µL/mL) demonstrated the greatest toxicity and feeding deterrence between constituents tested, respectively. Based on the fractional effects indices for the blends, a synergistic interaction was found for the blend of the Lippia and Schinus oils at a proportion of 75 and 25%, respectively. The present findings indicate that this blend could be used in the control of P. xylostella, as the literature reports populations resistant to the active ingredient in the positive control, Premio®. Further studies are needed for the development of a new botanical insecticide based on the active ingredients in oils from L. sidoides and S. terebinthifolius to improve efficiency, stability and the cost-benefit in the control of P. xylostella.

This work describes the chemical composition and bioactivity of essential oils and selected compounds belonging to the families Piperaceae, Myrtaceae and Rutaceae. GC-MS analysis of the oils enabled the identification of safrole, Dill apiole, (E)-nerolidol, 1,8-Cineole, Citronellal and limonene as major constituents of the oil of the Piper divaricatum, Piper aducum, Melaleuca, Eucalyptus globulus, Eucalyptus citriodora and Citrus, respectively. Among the essential oils tested, P. aduncum was the most toxic by residual contact, topical and ovicide assay on Spodoptera frugiperda. Among the chemical compounds, safrole was the most toxic by residual contact whereas citronellal was the most toxic in the topical assay and ovicidal activity. The antifeedant activity was found for the oils from Piper, Melaleuca, Syzygium, C. aurantiifolia var amara, C. limon and Safrol. This work showed that Piper oils are the most promising for future use for the control of S. frugiperda.

Essential oils from the leaves of four species of Piper obtained through hydrodistillation were analyzed using GC-MS andmultivariate data analysis. The chemical analysis enabled the identification of qualitative and quantitative differences among the oils. β-selinene (32.44 ± 1.14%), (E)-nerolidol (44.23 ± 2.23%), β-caryophyllene (19.11 ± 0.40%) and caryophyllene oxide (16.92 ± 0.21%) were identified as the major constituents of the P. mollipilosum, P. brachypetiolatum, P. glandulosissimum and P. madeiranum oils, respectively. The differences in the chemical profiles of the oils were confirmed by principal component analysis. All four species exhibited antioxidant activity. The oil from P. brachypetiolatum achieved the best results on the DPPH test (EC₅₀ = 64.8 µg/ml) and with the ABTS radical (EC₅₀ = 159.7 µg/ml).

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.