Lipid and polymeric nanocarriers as an approach to enhance the anti-inflammatory activity of essential oils

Abstract

Essential oils (EOs), which are mixtures of volatile compounds extracted from aromatic plants, have received attention as anti-inflammatory agents due to their ability to modulate multiple signaling pathways (e.g., the arachidonic acid pathway, cannabinoid receptors and cytokine regulation) and to reduce or even avoiding toxic side effects of synthetic drugs. Oregano, peppermint, clove, wintergreen, rosemary, tea tree, lavender, thyme and erva baleeira EOs have been widely used in this context. Despite the high efficiency, high volatility, hydrophobicity and oxidation of many terpenes found in these EOs, many challenges are found formulation development step, which have motivated the application of nanotechnologies such as lipid or polymeric nanocarriers. Lipid-based systems have the benefit of providing high encapsulation efficiency of hydrophobic terpenes and can improve interaction with cells or biological tissues. Polymeric nanoparticles, in turn, often result in more stable particles with greater release control. In addition to these advantages, enhanced anti-inflammatory activity can be achieved, which was exploited in detail in this review. Several topical formulations containing EO nanoparticles have been demonstrated to provide an in vivo anti-inflammatory effect similar or even higher than reference drugs such as indomethacin and dexamethasone, encouraging clinical trials. Besides anti-inflammatory effects, some EOs have antimicrobial and/or analgesic properties, making it possible to reduce the number of drugs used in inflammatory disorders associated with infection or pain (an important aspect from a safety standpoint). Another point that still deserves to be explored is the synergism of the anti-inflammatory action of EOs.