Development of a Multifunctional Phytocosmetic Nanoemulsion Containing Achillea millefolium: A Sustainable Approach

Skin aging, including photoaging, is primarily triggered by chronic exposure to solar radiation, which induces free radical formation, cellular deoxyribonucleic acid (DNA) damage, and structural skin alterations. Achillea millefolium L. (Asteraceae) is rich in phenolic compounds and alkamides, substances known for their antioxidant activity. This study aimed to develop and characterize a photoprotective phytocosmetic nanoemulsion containing crude root extract of A. millefolium. The extract exhibited a total phenolic content of 3.067 ± 1.911 µg GAE/mL, potent antioxidant activity (EC50 = 69.11 ± 8.899 µg/mL), moderate tyrosinase inhibition (19 ± 1.8%), and no cytotoxicity in keratinocytes. The extract was incorporated into nanoemulsions at concentrations of 0.1%, 0.5%, and 1%. The resulting droplets showed mean diameters of 217 to 230 nm, with a significant increase in the polydispersity index (PDI) after extract addition (p < 0.05). Transmission electron microscopy (TEM) confirmed the spherical morphology of the droplets. The in vitro sun protection factor (SPF) was 14 ± 0.9 in the control formulation and increased to 15 ± 2.0 (0.1%), 22 ± 5.2 (0.5%), and 17 ± 1.0 (1%), suggesting a synergistic effect between the extract and chemical filters. All formulations demonstrated UVA/UVB ratio > 0.6, a pH near to 5, occlusive properties, and good spreadability. The results indicate that A. millefolium extract holds potential for safe photoprotective formulations, offering a valuable antioxidant and depigmenting activity in addition to enhancing the SPF. This position is an innovative alternative to phytocosmetic development.