Development, characterization, and clinical investigation of Spinacia oleracea-based ultra-high pressure homogenized emulsion system for facial physiological parameters.

Background: Spinacia oleracea (SO) exhibits radical scavenging and tyrosinase inhibition activity indicating potential as a depigmenting agent.

Aims: To develop and characterize a stable emulsified system containing SO extract through ultra-high pressure homogenization, evaluate skin permeability, and enumerate in vivo performance in terms of melanin index, skin spots analysis, and related skin physiological parameters.

Method: Free radical scavenging and tyrosinase inhibition potential of SO extract was quantified through DPPH radical scavenging and mushroom tyrosinase inhibition assay, respectively. Six SO extract loaded ultra-high pressure emulsified systems (UHSO) were developed using ultra-high pressure homogenizer and assessed for size and polydispersity index (PDI). Among the prepared formulations, the optimized formulation (UHSO6) was subjected to 90 days stability studies performed at 8°C, 25°C, 40°C, and 40°C+75% RH (relative humidity) for organoleptic features, pH, and rheology. Ex vivo skin permeability studies were performed on abdominal skin from male albino rat. Changes in skin physiological parameters were evaluated in healthy female volunteers (n = 13) for 12 weeks utilizing mexameter , corneometer , and sebumeter . Skin spots were analyzed through computerized analysis of high-resolution images by visioFace .

Results: SO extract exhibited promising antioxidant (88±0.0096%) and tyrosinase inhibition potential (90.6 ± 0.0015 mg of Kojic Acid Eq/g of extract). Optimized UHSO was found to be stable with respect to stability evaluation, globule size (1110 nm), zeta potential (-27.6), and PDI (0.34). Ex vivo skin permeation of UHSO was significantly higher than SO loaded coarse emulsion. Moreover, the formulation showed a significant decrease in skin melanin, spot count, and spot % area, whereas skin hydration index was improved significantly.

Conclusion: Stable SO extract loaded emulsion system was successfully developed by a novel, cost-effective technique of ultra-high pressure homogenization which showed improved performance in terms of skin permeation and other skin physiological parameters.