Influência de distintos quimiotipos de Lippia alba na estabilização de nano-emulsões

Abstract

The plant species Lippia alba (Mill.) N.E.Br. ex Britton & P. Wilson, belonging to the Verbenaceae family, is popularly known as ‘erva-cidreira’ and is widely distributed throughout Brazil. This species is known for presenting a quantitative and qualitative variability in the chemical composition of its essential oil, presenting, therefore, different chemotypes. The chemical analysis of Lippia alba essential oil is of great importance because its constituents can affect characteristics such as its intrinsic solubility. In addition, nanostructured systems, including nano-emulsions, are an excellent alternative to optimize the characteristics of essential oil. Therefore, the objective of this work is to investigate the phenomena of generation and stabilization of nanodroplets from different chemotypes of Lippia alba, observing the influence of their chemical composition on the phenomena. The essential oils were extracted by the technique of hydrodistillation in a Clevenger-type apparatus and characterized by gas chromatography coupled to mass spectrometry. In this work, a low-energy approach was used to obtain nano-emulsions (citral and carvone chemotypes from Lippia alba). The nanoemulsions were prepared in two steps, initially by dispersing the essential oils in glycerin and then adding these systems to deionized water. The produced nano-emulsions were evaluated macroscopically and the droplet size distribution analysis was performed by dynamic light scattering in a Zetasizer Malvern NanoZS equipment, the measurements were performed in triplicate and the graphs were interpreted in terms of mean diameter and polydispersion index. An increase of 160% was observed about the droplet size of the nano-emulsions prepared with the carvone chemotype after 24h. When diluted, these nano-emulsions showed a droplet increase of around 65%. Although the nano-emulsions prepared with the citral chemotype showed a larger droplet diameter than the carvone chemotype, analysis of the diluted sample revealed a smaller increase in droplet size (~20%). This effect may be associated with a greater surface area and ease of migration of the droplet components of nano-emulsions based on the essential oil of the carvone chemotype. The present work allowed an investigation of the generation, formation, and stabilization of nano-emulsions based on essential oils, with an interpretation of the results in function of the differences in the phytochemical profiles of the different chemotypes