Óleo essencial nano estruturado de Pectis elongata Kunth: potencial antimicrobiano, anti-inflamatório e estimulante do reparo tecidual de feridas cutâneas

Abstract

Pectis elongata Kunth, it’s an herbaceous plant, knowledge on the Northern Brazil like "cuminho-bravo", "alecrim limão" or "alecrim-bravo". It´s a species rich in essential oil, which present as majority constituent, the citral, component with recognized pharmacological properties. Nevertheless, it is known that essential oils present low solubility and high volatility, limiting its use as a therapeutic agent. In such a way, the insertion of essential oils in nanostructured systems, such as nanoemulsions, may be a promising alternative to circumvent the limitations related to its use. In the present study, our proposal was to evaluate the efficiency of the process of nanoemulsification of P. elongata essential oil about the retention of its main volatile constituents, as well as on its antimicrobial properties, anti-inflammatory and stimulating the healing process of cutaneous wounds. For this, in the first step, after obtaining the essential oil by hydrodistillation, the nanoemulsification process was performed using the low energy method and Tween80 as surfactant, resulting in particles with nanometric size (109.7 ± 1.4 nm), low polydispersity index (0.182 ± 0.00) and negative zeta potential (-32.3 ± 1.2 mV). These results characterize it as a nanoemulsion with uniform size distribution and repulsion forces strong enough to prevent coalescence between particles; properties that ensure its physical stability. To investigate the protection exercised by the nanostructured system against volatilization of the main components present in the essential oil of P. elongata, we determined the chemical composition of the free and nanoemulsified oil, using techniques of gas chromatography coupled to mass spectrometry. In this stage, the samples were stored under temperature of 25°C, during the period of 12 months, being the chemical analyses of the nanoemulsions performed at 0, 7-, 15-, 60- and 360-days post-preparation. The results showed citral as the major constituent for all samples analyzed where, in the free oil, the concentration of this compound was determined in 92.5%; and in the nanostructured system, in the post-preparation times quoted, the concentration of citral was determined in 92.8%, 92.6%, 90.8.0%, 95.7% and 78.9%, respectively. In the next step, we used the broth microdilution method to determine the Minimum Inhibitory Concentration (MIC) and the Minimum Bactericidal Concentration (MBC) of the nanostructured essential oil, in the face of bacteria of interest in public health, which interfere in the process of cutaneous wound healing. The standard strains selected for study were Streptococcus pyogenes S012, Staphylococcus epidermidis S010 and Staphylococcus aureus S008. In this test, it was decided to evaluate the antimicrobial potential of nanoemulsions stored at 25°C, at the initial and final times of the storage period (0 and 360 days, respectively). It was verified that there was no significant loss of its antimicrobial potential after 360 days of storage. Finally, the anti-inflammatory activity was evaluated by the carrageenan-induced paw edema test, and the stimulating potential of the cicatricial process was evaluated on skin wounds induced by surgical incision. The anti-inflammatory activity of the nanoemulsion was observed only for the dose of 10 mg mL-1, presenting significant results when compared to the negative control (distilled water). In the healing results, no significant increase in the percentage of wound contraction was observed when compared to the negative control (sterile saline solution). From these results, it is possible to suggest that the process of nanostructuring the essential oil of P. Elongata, using the technique of low energy input, was able to produce a physically stable nanoemulsion, showing effectiveness both in maintaining its chemical properties and in preserve its biological properties, inhibiting the growth of microorganisms and modulating the inflammatory response induced by carrageenan. On the other hand, at the concentrations evaluated, the nanoemulsion was not able to accelerate the contraction process of skin wounds.