Nanoemulsions of essential oils to improve solubility, stability and permeability: a review

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Nanoemulsions of essential oils to improve solubility, stability and permeability: a review Thaís Nogueira Barradas1   · Kattya Gyselle de Holanda e Silva2 Received: 29 October 2020 / Accepted: 11 November 2020 © Springer Nature Switzerland AG 2020

Abstract There is a growing society demand for healthier, safer and environmental-friendly products. For instance, essential oils are emerging as a natural alternatives for replacing synthetic pharmaceuticals. Essential oils have indeed proven in vitro pharmacological activities to treat various diseases. Nonetheless, the application of essential oils is limited by their low solubility, low bioavailability, low permeability, uncontrolled volatility and low long-term stability. These issues can be solved by encapsulation of essential oils in nanoemulsions. Nanoemulsions display unique properties such as nanometric size, increased surface area and stability, which increase the efficiency of pharmaceutical dosage. Here we review nanoemulsion formulations, types of surfactants and oils, and their applications for essential oils encapsulation. We present methods to produce nanoemulsions such as high-pressure homogenization, microfluidizers, ultrasonic homogenization, phase inversion composition and phase inversion temperature. We also discuss nanoemulsion instability. Keywords  Nanoemulsions · Nanoencapsulation · Surfactants · Emulsification methods · Essential oils · Drug delivery

Introduction The clinical application of natural bioactive molecules is an alternative therapeutical approach, because bioactive agents are regarded as safer when compared with the synthetic molecules (Saka and Chella 2020). Such escalade in the application of these natural-based bioactive molecules brings a further need for the research in the development of suitable and stable formulations. Essential oils are bioactive molecules, considered safe and biocompatible with a great range of therapeutic applications due to their heterogeneous composition of fatty acids, terpenes, triterpenes and many other lipophilic components, that offer protection against skin dehydration, solar radiation, inflammation, insect

* Thaís Nogueira Barradas [email protected] 1



Faculdade de Farmácia - Universidade Federal de Juiz de Fora, R. José Lourenço Kelmer, s/n Bairro São Pedro, Juiz de Fora 36036‑900, Brazil



Programa de Pós‑Graduação Em Nanobiossistemas, Ilha do Fundão, Universidade Federal do Rio de Janeiro, Cidade Universitária, Av. Carlos Chagas Filho, 373, Rio de Janeiro 21941‑902, Brazil

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attack, microorganisms, and viruses (Andreu et al. 2015; Donsì and Ferrari 2016; Bonferoni et al. 2017). Most essential oils can prevent oxidation reactions, reducing the formation of free radicals, which can cause cellular damage and chronicle diseases as cancer. However, the clinical application of essential oils is limited by technological issues, as they are difficult to incorporate into a pharmaceutical product lies due to their low water solubility. Moreover, their bioavailability and stabi