Incorporation of Eugenia dysenterica extract in microemulsions preserves stability, antioxidant effect and provides enhanced cutaneous permeation

Abstract

The aim of this paper was to develop stable, non-irritant topical formulations for the incorporation of aqueous extract from Eugenia dysenterica leaves, which could improve cutaneous permeation without compromising its antioxidant activity. For this, O/W and W/O microemulsions were obtained. Droplet sizes varied from 175 nm to 208 nm for the O/W formulations and from 27 nm to 35 nm for the W/O microemulsions, with PDI values below 0.2. Nanoformulations implemented a significant improvement in the stability of catechin over 90 days compared to simple solutions of the actives, especially the W/O microemulsions, which remained a catechin content of 96.1% and 96.6% (for the formulations containing the extract or the isolated catechin, respectively) when the formulations were stored at 6 °C, while the respective controls remained only 66.7% and 94.4% of catechin at the same storage conditions. All nanoformulations were capable of significantly increasing the penetration of catechin into skin, with emphasis on the O/W microemulsions, which proved to significantly increase the penetration of catechin to the deeper layers of the skin, compared to controls. The antioxidant activity of the active substances was maintained with the formulation in microemulsions, and the formulations containing the extracts presented superior activity to those containing the isolated catechin. All microemulsions presented low irritability potential. In conclusion, the microemulsions containing the aqueous extract of E. dysenterica leaves seem to be promising systems for topical application, which enables their use in dermatological treatments that require antioxidant action.