Effectiveness and irritability study of glabridin nanoemulsion with oleic acid-EVO oil and oleic acid-palm oil as an oil phase

Glabridin, an isoflavan primarily found in licorice extract, is widely recognized for its skin-lightening properties. However, its effective use is limited by poor solubility, low stability, and inadequate skin penetration. To overcome these limitations, Glabridin was incorporated into a nanoemulsion as a novel delivery system. In this study, Glabridin was formulated in Oil-in-Water (O/W) nanoemulsion using oleic acid as an oil phase, both alone and combination with extra virgin olive (EVO) Oil, and palm oil, at a weight ratio of 1:3. The nanoemulsion was characterized based on mean droplet diameter (MDD), polydispersity index (PDI), transmittance, organoleptic, and entrapment efficiency. The irritability of the formulation was evaluated using Hen’s Egg Test on the Chorioallantoic Membran (HET-CAM) assay. Additionally, an in-vivo study on 15 human subjects to assess the skin-lightening effect of glabridin nanoemulsion, was applied twice daily to the left forearm for four weeks. The results indicated that oleic acid alone produced a larger droplet size and lower transmittance to the other formulations. All formulations were within the non-irritant range according to the HET-CAM test. The study demonstrated a reduction in melanin levels and increased ITA (individual topology angular), which corresponds to the Fitzpatrick skin phototypes. Notably, The combination of Oleic acid and Palm oil resulted in a significant reduction in melanin content and improved skin tone, confirming the potential of this formulation to achieve skin-lightening effect.