Hydrogel-thickened nanoemulsion containing amazonian Aniba canelilla (Kunth) Mez essential oil: Skin permeation and in vivo anti-inflammatory efficacy

The essential oil of Aniba canelilla (Kunth) Mez has 1-nitro-2-phenylethane (NP) and methyleugenol (ME) as major compounds. Despite the folk medicine practices and scientifically proven anti-inflammatory activity in treating skin disorders, there is no report of the development of a semisolid pharmaceutical form containing essential oil of A. canelilla. To reduce volatility from essential oils, enhance activity and control release, a nanoemulsion containing essential oil of A. canelilla was developed. Hydrogel-thickened nanoemulsions may increase nanoemulsion viscosity and adhesiveness favoring its stability beyond suitability to skin application. In this way, hydroxyethylcellulose and chitosan hydrogels-thickened nanoemulsion containing essential oil of A. canelilla were developed. Formulations were characterized by their droplet size, polydispersity index, zeta potential, pH, transmission electron microscopy, release studies and skin permeation essays were also performed. Both hydrogels presented an adequate stability with low droplet size during 120-days storage, controlled release profile, and were able to deliver the main compounds of the essential oil, 1-nitro-2-phenylethane and methyleugenol, in great amounts to the dermis. Cutaneous anti-inflammatory potential, myeloperoxidase activity and interleukins content were also investigated. Hydroxyethylcellulose-hydrogel thickened nanoemulsion containing essential oil of A. canelilla seemed to be a promising formulation since it showed an evident anti-inflammatory response with reduced MPO activity and interleukins content suggesting activity by decreasing edema, lowering polymorphonuclear leukocytes migration and reducing synthesis/release of inflammatory mediators mainly attributed to the essential oil compounds.