Preliminary safety and in vivo efficacy of Acmella oleracea extract-loaded glycolipid emulsion serum-Effects on ocular irritation, dermal absorption, and facial skin biophysical and microrelief properties.

Objective: Substantial efforts have been progressively devoted to developing innovative, safe, and effective topical anti-aging products that not only improve the appearance of aged skin but also prioritize environmental sustainability and the responsible use of natural resources. Thus, the current study targeted to evaluate novel, natural emulsion/serum comprising new glycolipid emulsifier (lauryl glucoside/myristyl glucoside/polyglyceryl-6 laurate) and Acmella oleracea plant extract as a model active.

Methods: The developed serum was assessed concerning its stability (freeze-thaw test, accelerated study), safety (in vitro screening of eye irritation potential, dermal absorption study) and efficacy (randomized, active/reference-controlled, half-face, in vivo study). Changes in skin biophysical properties, microrelief, roughness, texture, surface, and volume parameters were assessed in the periocular and perioral areas of human volunteers after 2 weeks of product application, utilizing several bioengineering and topography techniques.

Results: The stability study demonstrated favourable stability profile of the developed serum, with practically unaffected stability-indicating parameters (apparent viscosity, yield, flow point, storage and loss moduli, loss factor, pH, electrical conductivity) during freeze-thaw cycling and after 3 months of storage at 45°C. The hen's egg test on the chorioallantoic membrane of fertilized chicken eggs confirmed the absence of ocular irritation potential of investigated serum; no effects of haemorrhage, lysis or coagulation were occurred. Skin permeation study using diffusion cells revealed no permeation of spilanthol from the tested A. oleracea extract-loaded serum through the pig ear skin into the receptor medium, thus suggesting no absorption into systemic circulation. In vivo efficacy study corroborated beneficial effects of evaluated serum on the condition/appearance of facial skin, at both periocular and perioral areas-significant (p < 0.05) increase in skin hydration (10%-40%) and smoothness (~15%); significant (p < 0.05) decrease in roughness (20%-30%), scaliness (~30%), and wrinkles (~15%)-implying more hydrated, smoother, visibly milder skin.

Conclusion: The present findings confirmed the stability, preliminary safety (no ocular irritation, no dermal absorption, and good skin tolerability), and efficacy (improved skin hydration and microrelief) of the A. oleracea extract-loaded, glycolipid-based serum, supporting its potential as a safe and effective topical anti-aging product.