Optimization of Actinopyga lecanora hydroysates-loaded nanoemulsion formulation

Actinopyga lecanora hydrolysates (ALH), rich in hydrophobic amino acids with antioxidant and anti-tyrosinase properties, have poor solubility and limited applicability on skin. This study optimized an ALH-loaded nanoemulsion using a five-factor D-optimal mixture design, with particle size selected as the response. The independent variables were oil phase (SO: AO, 9:1), ALH, surfactant mix (Tween 80:Span 80, 8:2), xanthan gum, and water. The quadratic model showed excellent fit (F = 249.03, p < 0.0001, R2 = 0.9956) with no significant lack of fit, confirming its reliability. The optimized formulation (SO: AO 10.00%, ALH 1.00%, T80:S80 13.75%, xanthan gum 0.87%, water 73.69%) produced a particle size of 139.80 nm, in close agreement with the predicted value of 137.30 nm (RSE = 1.79%). The nanoemulsion exhibited pseudoplastic behaviour with a pH of 5.38 and good storage stability. In vitro permeation showed 66.48% ALH release after 8 h, while antioxidant (DPPH and FRAP) and anti-tyrosinase activities increased significantly (p < 0.05) compared with blank formulations. Overall, the validated D-optimal design successfully produced a stable and bioactive ALH nanoemulsion with particle size within the optimal range (100–200 nm) for cosmetic application, supporting its potential use as a cosmeceutical ingredient.