Niosomal formulation of hydroxytyrosol, a polyphenolic antioxidant, for enhancing transdermal delivery across human cadaver skin

Hydroxytyrosol (HT), a naturally occurring polyphenol from the olive plant, is a potent antioxidant, cardioprotective, neuroprotective, and anti-inflammatory agent. Upon oral administration, HT undergoes rapid elimination within minutes and thus limiting its therapeutic utility. Due to its hydrophilic nature, percutaneous absorption and transdermal delivery of HT are very low. The aim of this research was to enhance the skin permeation of hydroxytyrosol using a niosome gel formulation. The formulations prepared with Span 60 as surfactant showed uniform particle size and high encapsulation efficiency (>90%). The niosome formulations showed a pseudoplastic behavior for topical application within the lipid/surfactant composition of 45-50%. The formulations showed a controlled release of HT compared to the HT solution. The flux of HT across human skin was increased by 28 and 4.4 fold compared to aqueous and ethanolic HT solutions, respectively (p < 0.001). The presence of lecithin lowered the flux and increased the retention of the formulations compared to HT solutions (p < 0.001). The formulations containing lecithin showed two-fold higher skin retention of hydroxytyrosol (p < 0.05). In conclusion, this study demonstrates niosome gel as a promising alternative to oral delivery of HT, providing sustained delivery and greater efficacy.