Development of a model system to study fuel autoxidation in supercritical media: decomposition kinetics of 2,2′-azobis(isobutyronitrile) in supercritical carbon dioxide

Abstract

Lippia sidoides (Verbenaceae) is a medicinal plant from Northeastern Brazil, whose essential oil is rich in thymol, being a well-known antimicrobial phenol compound. The aim of this study was to produce suspensions of polycaprolactone (PCL)-coated nanocapsules incorporated with the essential oil from the L. sidoides leaves (EOLS) by the emulsion-diffusion method. EOLS nanocapsules were prepared by mixing EOLS and PCL with Kolliphor P 188® as the surfactant and ethyl laurate (core oil), all of them in varying concentrations (1, 2.5 and 5%). The said nanoformulations were assessed for their particle size and encapsulation efficiency (EE). The best condition was achieved with the nanoformulation containing 1% Kolliphor P 188®, 2.5% polycaprolactone, 2.5% EOLS and 5% ethyl laurate, emulsified at 10,000 rpm for 5 min, which presented an average particle diameter with 173.6 nm, a polydispersity index of 0.2 and an EE of 70.6%. Additionally, the nanoemulsion was characterized by the nuclear magnetic resonance (1H and diffusion-ordered NMR spectroscopy- DOSY), scanning electron microscopy, thermogravimetry and the differential scanning calorimetry. Furthermore, the suspension of nanocapsules of the EOLS was demonstrated to be stable at 5 °C during 60 days of storage in an accelerated stability study.