Sistema microemulsionado contendo óleo de pequi (Caryocar coriaceum Wittm) para uso tópico anti-inflamatório

Abstract

Pequi is a fruit from an angiosperm popularly known as pequizeiro (Caryocar coriaceum W.), found in the Brazilian cerrado and semi-arid biomes. The oil obtained from the pulp, has unsaturated fatty acids (UFAs), with potential antioxidant and anti-inflammatory properties, minerals and vitamins, being widely used in popular medicine. It’s incorporation in microemulsion systems (MES) can allow major therapeutic effectiveness by the drug delivery system ability to interact with the stratum corneum of the skin. In search for an innovative and efficient topical anti-inflammatory therapy, the objective of this work was the development and characterization of a ME containing pequi pulp oil. In face of that, the oil was extracted, chemically described and had its Hydrophilic-Lipophilic Balance (HLB) determined. Thereupon, a Pseudoternary Phase Diagram (PTPD) was developed for the obtainment of transparent systems. Among these, a system was selected and characterized in the aspects of pH, conductivity, refractive index, viscosity, droplet size, zeta potential, morphology, thermal properties and preliminary physical stability. Finally, preliminary anti - inflammatory activity in rat paw edema model using carrageenan was verified and a histological study was made. The results pointed the presence of the majority oleic and palmitic UFA, while the oil HLB was determined in between 10,5 - 11,75. The PTPD was obtained by the use of Kollyphor EL® e Brij 52 ® , pequi oil and aqueous phase (water and propyleneglycol - 1:3), being selected a system composed by 47,6% of the tensoactives mixture, 5,3% of pequi oil and 47,1% of aqueous phase. Macroscopically, the system demonstrated homogeneous and transparent aspect. The pH value obtained (7,33 ±0,04) was adequate for topical application, while the refractive index and polarized light microscopy revealed an isotropic formulation. Rheological studies indicated Newtonian flow, whereas the medium droplet size was 13,38 nm with unimodal distribution and dispersity 0,17, characteristics which, added to the zeta potential measure of │7,53 δmV│, are indications of a stable ME. The transmission electron microscopy (TEM) revealed droplet groups of oil covered by tensoactives. The electrical conductivity was relatively low (15,087±0,1893 μS cm ), justified by the major propyleneglycol presence in the aqueous phase. These findings indicate a ME behavior of bicontinuous transition phase system to W/O, confirmed by DSC. The formulation remained stable in previous stability studies realized. Furthermore, during the in vivo study, the group treated with the ME containing 5,3% of pequi oil presented superior edema inhibition (p<0,05) during the first two hours while compared to the other groups, besides maintaining superior activity than the brute oil during the whole study . The histological analysis corroborates this result, since the group treated with the ME revealed reduced histopathological findings. Therefore, the developed nanosystem demonstrated to be stable, with desirable aspects for topical usage and with high anti-inflammatory action, being a promising nanotechnological phytotherapic and an alternative to the usual treatments for cutaneous inflammations.