Pomegranate peel and seeds have demonstrated to possess antioxidant compounds with potential application to protect the skin against the ultraviolet radiation damage. However, the photoprotection activity is dependent on the amount of these compounds that reach the viable skin layers. In this paper, we describe the in vitro skin permeation and retention of the major pomegranate peel polyphenols using Franz diffusion cells, after entrapping a ethyl acetate fraction (EAF) from Punica granatum peel extract into nanoemulsions (NEs) prepared with pomegranate seed oil (PSO) or medium chain triglyceride oil (MCT). The in vitro skin permeation of gallic acid (GA), ellagic acid (EA), and punicalagin (PC) was evaluated using a HPLC-DAD validated method. After 8 h of skin permeation, all polyphenol compounds were mostly retained in the skin and did not reach the receptor compartment. However, a 2.2-fold enhancement of the retained amount of gallic acid in the stratum corneum was verified after EAF-loaded NEs are applied, when compared with the free EAF. GA and EA were delivered to the viable epidermis and dermis only when nanoemulsions were applied onto the skin. The mean retained amounts of GA and EA in the EP and DE after applying the EAF-loaded PSO-NE were 1.78 and 1.36 μg cm-2 and 1.10 and 0.97 μg cm-2, respectively. Similar values were obtained after applying the EAF-loaded MCT-NE. The skin permeation results were supported by the confocal microscopy images. These results evidenced the promising application of nanoemulsions to deliver the pomegranate polyphenols into the deeper skin layers.
Keywords: Punica granatum; confocal microscopy; nanoemulsions; polyphenols; skin permeation.