Avaliação biológica e mecanismo de ação dos óleos essenciais das espécies vegetais Prunus persica e Satureja montana sobre Escherichia coli, Staphylococcus aureus e Penicillium expansum

Abstract

Natural products are considered promising antifungal, antioxidant, antibacterial, and anti- inflammatory agents, leading to their increased exploration. Essential oils, formed from

secondary metabolism, serve as a notable example. The objectives of this study were to extract, chemically characterize, and evaluate the antioxidant and antifungal activity, as well as to study the mechanism of action of the essential oils from Prunus persica (peach tree) and Satureja montana (savory) on the bacteria Escherichia coli and Staphylococcus aureus. Antioxidant evaluation was performed using the DPPH assay, β-carotene bleaching test, and reducing power assay. Fungal analysis was conducted using the disk diffusion method, and the mechanism of action was assessed through various methods, including potassium ion efflux, decreased salt tolerance capacity, leakage of cellular contents absorbing at 260 nm, and crystal violet uptake. The altered bacterial morphology caused by the essential oils was analyzed using Scanning

Electron Microscopy (SEM). The major constituents of savory essential oil were carvacrol, p- cymene, and hexadecanol, while peach leaf essential oil primarily contained benzaldehyde.

Both oils exhibited bactericidal and bacteriostatic effects. Savory essential oil demonstrated strong antioxidant and antifungal potential. Neither oil induced potassium ion efflux in bacterial cells. Savory oil caused a reduction in salt tolerance in both bacteria, unlike peach leaf oil. Leakage of cellular constituents was observed for both oils, except for savory oil on E. coli. Crystal violet uptake was more pronounced with peach oil than with savory oil, which showed only slight variation. SEM images revealed that both oils were capable of reducing the number of bacterial cells. It was concluded that savory oil showed significant antioxidant, antifungal, and antibacterial potential, while peach leaf oil exhibited lower antioxidant potential and lesser antifungal and antibacterial activity. Thus, the mechanism of action of the oils on bacteria can be attributed to direct or indirect alterations in membrane permeability.