Avaliação In vitro da atividade antimicrobiana do óleo essencial das folhas de Ayapana triplinervis e de seu sistema nanoemulsionado

Abstract

Essential oils are products of secondary plant metabolism and known for their antimicrobial properties, but suffer from the disadvantages of being volatile and difficult to incorporate into aqueous solutions due to their lipophilic nature. Nanoemulsions consist of nano-sized droplets stabilized by emulsifiers, and although thermodynamically unstable they are more permeable due to their smaller particle sizes and larger surface area, which can circumvent the disadvantages of the essential oil and enhance its effects. Thus, the aim of this work was to evaluate the antibacterial action of the essential oil from the leaves and nanoemulsion of Ayapana triplinervis species. Nanoemulsions with essential oil were prepared by a low energy input method, and their physicochemical characterization as well as particle size distribution were evaluated by photon correlation spectroscopy (PCS) and surface charge (zeta potential) electrophoretics. The antibacterial activity was evaluated using the microdilution method on Gram-positive (Staphylococcus aureus and Enterococcus faecalis) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacterial strains. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined using resazurin assays. The nanoemulsion of the essential oil of morphotype A showed particle size of 175.37 ± 3.60 nm (polydispersity index 0.369 ± 0.046 and zeta potential equal to -45.7 ± 4.68 mV), and the nanoemulsion of the essential oil of morphotype B showed particle size of 162.20 ± 0.66 nm (polydispersity index equal to 0.377 ± 0.025 and zeta potential of - 42.7 ± 5.08 mV). The results indicated that the essential oil and nanoemulsified system of Ayapana triplinervis did not show antimicrobial potential at the tested concentrations