Development of nanoemulsions containing Lavandula dentata or Myristica fragrans essential oils: Influence of temperature and storage period on physical-chemical properties and chemical stability

Essential oils are characterized as complex compound mixtures with important pharmacological properties, yet they are sensitive to high temperatures, light, and the presence of oxygen. Nanotechnology is therefore used to improve stability, securing both quality and efficacy. To evaluate the stability of Lavandula dentata Linnaueus and Myristica fragrans Houtt essential oils when associated with nanostructures, nanoemulsions containing 5% essential oil with hydrophilic and lipophilic surfactants were developed through emulsification under high agitation. Fabrication of the formulations did not qualitatively or quantitatively affect the majority of the essential oil compounds being identificates by gasose cromatografy as main constituents (-) - β-pinene (24–31 %), 1-terpinen-4-ol (14–15 %), L- α-pinene (13 %) and sabinene (10–15 %), in M. fragrans; e 1.8 cineol (50–52 %), fenchone (17−16 %) and camphor (15–13 %) for L. dentata. The systems were characterized in terms of average droplet size, polydispersity index, pH, zeta potential, and each essential oil's chemical composition (upon preparation), and for 90 days under the following storage conditions: refrigeration temperature, room temperature, and a controlled climatic chamber. After preparation: the droplet size of M. fragrans esential oil-loaded nanoemulsion (NE–MO) was 87.06 ɳm, its polydispersity index (PDI) was 0.17, the zeta potential value was -14.8 mV, and the pH was 5.62; L. dentata esential oil–loaded nanoemulsion (NE–LO) droplet size was 64.99 ɳm, its polydispersity index (PDI) was 0.26, zeta potential value was –11.1 mV, and the pH was 4.95. Investigation of these physicochemical response (particle size and polydispersity index) suggests that NE–MO presented intended responses and good stability over 3 months’ and 15 days storage at refrigeration and room temperature, respectively; being that the pH of formulation was maintained unaltered in the three conditions. Produced nanoemulsions with essential oil of Lavandula dentata presented physicochemical stables response in period of 3 months’ and 7 days torage at refrigeration and room temperature, respectively; but pH value was maintained unaltered only up to 15 days in refrigeration. Chemical analyses proved the greater efficacy of the NE–MO to preserve the majority compound percentages oil (L-α-pinene, (-)-β-pinene, sabinene, α-limonene, γ-terpinene) throughout the study under storage at 4 and 24 °C compared with free oil. The formulation NE–LO enabled good protection only at room temperature for α-pinene, sabinene 1.8-cineole, fenchone and camphor. However, this formulation not presented stables physicochemical characteristics during the study at room temperature. In summary, the nutmeg oil–loaded nanoemulsion was successfully formulated and its protection profile ensured essential oil chemical stability. © 2020 Elsevier B.V.