Essential oils in nanostructured systems: Challenges in preparation and analytical methods

Essential oils are natural products extracted from plants that present volatile and thermolabile characteristics. Essential oils have become products of interest in many fields, including the pharmaceutical, due to their medicinal properties. In recent years, the interest in the encapsulation of essential oils in nanometric systems for therapeutic approaches has risen and a number of studies have been published. This review intended to set a panorama on the research within this field through a data survey and identify the organic nanostructured systems, the preparation techniques and analytical quantification methods employed. Many techniques used to prepare nanosystems loaded with essential oils involve heating or solvent evaporation steps that may damage their composition. In this context, the quantification of essential oil on the final nanosystems is impaired. However, in more than half of the research papers, the quantification is ignored or an indirect quantification is performed, assuming no volatilisation upon formulation processes. Analytical methods used to assess essential oil encapsulation efficiency were discussed regarding their suitability. [Display omitted] •A data survey was done to set a panorama of the research concerning the nanoencapsulation of EO for medicinal purposes.•Encapsulation of EO in nanosystems has been studied in the last decade and raised in 2015 and the following years.•Nanoencapsulation of EO many times involve heating and solvent evaporation steps, causing volatilization and/degradation.•Many studies evaluated do not perform the quantification of chemical markers on the EO after the nanoencapsulation.•Among the studies that quantify EO, a few techniques are employed, but not always suitable for the purpose.