Purpose: The aim of this study was to characterize the undecylenoyl phenylalanine (Sepiwhite (SEPI))-loaded nanostructured lipid carriers (NLCs) as a new antimelanogenesis compound. Methods: In this study, an optimized SEPI-NLC formulation was prepared and characterized for particle size, zeta potential, stability, and encapsulation efficiency. Then, in vitro drug loading capacity and the release profile of SEPI, and its cytotoxicity were investigated. The ex vivo skin permeation and the anti-tyrosinase activity of SEPI-NLCs were also evaluated. Results: The optimized SEPI-NLC formulation showed the size of 180.1±5.01 nm, a spherical morphology under TEM, entrapment efficiency of 90.81±3.75%, and stability for 9 months at room temperature. The differential scanning calorimetry (DSC) analysis exhibited an amorphous state of SEPI in NLCs. In addition, the release study demonstrated that SEPI-NLCs had a biphasic release outline with an initial burst release compared to SEPI-EMULSION. About 65% of SEPI was released from SEPI-NLC within 72 h, while in SEPI-EMULSION, this value was 23%. The ex vivo permeation profiles revealed that the higher SEPI accumulation in the skin following application of SEPI-NLC (up to 88.8%) compared to SEPI-EMULSION (65%) and SEPI-ETHANOL (74.8%) formulations (P<0.01). An inhibition rate of 72% and 65% was obtained for mushroom and cellular tyrosinase activity of SEPI, respectively. Moreover, results of in vitro cytotoxicity assay confirmed SEPI-NLCs to be non-toxic and safe for topical use. Conclusion: The results of this study demonstrate that NLC can efficiently deliver SEPI into the skin, which has a promise for topical treatment of hyperpigmentation.

Background: Hyperpigmentation is darkened patches or spots on the skin occurred by increased melanin. Undecylenoyl phenylalanine (Sepiwhite®), as a commercial lipophilic derivative of phenylalanine, is a powerful new brightener that can be used in the treatment of skin pigmentation disorders.Aims: Solid lipid nanoparticles (SLNs) increase the efficiency of hydrophobic drugs. The current study aimed to prepare and characterize SLNs containing Sepiwhite (SEPI-SLN).Methods: In this study, an optimized SEPI-SLN formulation was selected by applying the response surface method. In vitro drug loading content, the release profile of SEPI, and cell viability were investigated. The permeation rate of SEPI-SLN was also compared to conventional cream containing Sepiwhite (SEPI-CREAM). Furthermore, the anti-tyrosinase activity of Sepiwhite was also evaluated. Results:The optimized formulation showed a spherical morphology with particle size and entrapment efficiency of 218.6 ± 11.1 nm and % 87.31 ± 0.65, respectively. Differential scanning calorimetry (DSC) analysis confirmed SEPI-loaded SLN formulation with no drug-lipid incompatibility. The in vitro permeation experiment revealed the enhanced cutaneous uptake of SEPI-SLN. The results also showed that Sepiwhite could stop melanogenesis with inhibition of the tyrosinase enzyme. Conclusion:Our findings confirm that SLNs could be a proper nanocarrier for the relevant usage of Sepiwhite as a powerful brightener agent.

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