Delineamento de microemulsões contendo óleo essencial de aroeira (Schinus terebinthifolius Raddi)

Abstract

Schinus terebinthifolius Raddi, popularly known as Aroeira, is a species native to Central and South America that produces Aroeira essential oil (AEO) widely used in traditional Brazilian medicine and with antimicrobial, antifungal, antitumor, antinociceptive activities, among others. However, the use of OEA in natura may have some limitations due to the easy degradation of the EO, volatility and low solubility. Thus, an alternative would be its encapsulation in MEs. MEs are defined as isotropic and thermodynamically soluble systems capable of solubilizing hydrophilic and lipophilic substances, preventing oxidation and hydrolysis of their actives, increasing skin permeation, etc. The objective of this work was the extraction, encapsulation and characterization of OEA in MEs, as well as the evaluation of the cytotoxic activity of the in natura oil of the proposed MEs. Initially, AEO was extracted from unripe (AEO 1) and ripe (AEO 2) fruits through the hydrodistillation process. Then, the phytochemical study of AEOs was carried out using the techniques of Nuclear Magnetic Resonance (NMR) and Gas Chromatography coupled with Mass Spectrometry (GC-MS). Subsequently, a Pseudoternary Phase Diagram (PPD) was constructed using the aqueous phase titration method to obtain the MEs. Then, the physical-chemical physical-chemical characterization (pH, conductivity and centrifugation) was carried out; morphological (droplet size, PDI, Zeta Potential, Polarized Light Microscopy (MLP) and rheological. Lastly, the in vitro cytotoxic activities of the proposed AEOs and MEs were evaluated. The main components of AEO1 were α-pinene (29.16%), dl-Limonene (20.65%) and ρ-cymene (15.86%), while l-phelandrene (38.91%), Silvestrene (23 .02%) and α-pinene (21.62%) were the major components of AEO 2. Based on the region in the oil-in-water (O/W) region of the PPD, the selected ME (MEB) was composed of distilled water (54.1%), capric-caprylic acid triglycerides (CCAT) (5.5% ), Kolliphor HS-15 (36.36%) and Transcutol (4.04%). Since, 2% of AEO were added to the MEB to obtain ME1 and ME2 for the presence of AEO in green and ripe fruits, respectively. MEs are translucent and stable liquid. The pH values were compatible with the topical route, observing 6.53±0.01 (MEB), 6.35±0.04 (ME1) and 6.38±0.03 (ME2). The smallest droplet size evidenced was for MEB (16.75±0.13 nm), with an increase after OEA encapsulation for ME1 (17.77±0.12 nm) and ME2 (17.98±0. 19 nm), both with PDI values of 0.01, 0.09 and 0.15, respectively. Electrical conductivity results indicated a suggestive structure of O/W droplets for both MEs. The rheology attested a Newtonian-like behavior for all tested samples. AEO1 showed cytotoxic activity at 37.5 and 18.7 μg/mL for SK-MEL-28 and HL-60, respectively. On the other hand, AEO2 showed cytotoxic activity against HL-60 at 100 μg/mL. Finally, none of the MEs showed cytotoxic activity in the tested cells. Thus, the results suggest a relevant cytotoxic activity for the AEO obtained, but that the proposed MEs need optimization in order to guarantee the cytotoxic activity of the OEA.