Abstract:

Peppermint essential oil nanoemulsion （PEO-NE）, a widely used ingredient in the cosmetics industry, holds significant potential for skincare applications. However, its practical use in aqueous-based formulations is severely limited by its inherent volatility, water insolubility, and low bioavailability. To address these challenges, six surfactants commonly employed in cosmetic emulsions were selected to fabricate PEO-NEs. The anti-wrinkle efficacy of the resulting nanoemulsions was assessed through both biochemical assays-namely the scavenging of DPPH and ABTS free radicals, and the inhibition of elastase activity- and cell-based biological evaluations involving collagen secretion measurements in a human fibroblast model under UVA-induced stress. The findings reveal that employing PEG-40 hydrogenated castor oil as the surfactant enables the successful preparation of a uniformly dispersed, clear, and transparent PEO-NE with an average particle size of 22.5 nm. Biochemical analyses demonstrate that the nanoemulsion exhibits pronounced antioxidant activity, effectively scavenging both DPPH and ABTS free radicals. Specifically, a 4% （V/V） PEO-NE formulation achieves a DPPH scavenging rate of 93.68%, with a corresponding IC₅₀ value of 1.29%. Meanwhile, a 1% （V/V） PEO-NE formulation achieves an ABTS scavenging rate of 84%, with a corresponding IC₅₀ value of 0.31%. Furthermore, the nanoemulsion significantly inhibits elastase activity in vitro, indicating its potential to delay elastin degradation. Cell-based experiments confirmed that the PEO-NE markedly promotes collagen secretion in a UVA-damaged human fibroblast model. In conclusion, the PEO nanoemulsion formulated with PEG-40 hydrogenated castor oil demonstrates compelling anti-wrinkle effects, supporting its suitability as a functional ingredient in cosmetic products aimed at improving skin elasticity and reducing signs of aging.

Key words: peppermint essential oil, nanoemulsion, anti-wrinkle, anti-aging