Preparation and Characterization of Nanostructured Lipid Carriers (NLCs) Containing Extract for the Treatment of Skin Hyperpigmentation.

PURPOSE

This study aimed to prepare, characterize, and and evaluate a novel nanostructured lipid carriers (NLCs) formulation containing two fractions of L. (licorice) extract for the treatment of hyperpigmentation.

METHODS

Two fractions, one enriched with glabridin (FEG) and the other enriched with liquiritin (FEL), were obtained by partitioning the methanol (MeOH) extract of licorice roots with ethyl acetate (EtOAc) and partitioning the EtOAc fraction with butanol (n-BuOH) and water. The quantities of glabridin (Glab) and liquiritin (LQ) in the fractions were determined by high-performance liquid chromatography (HPLC). FEG and FEL were loaded in different NLC formulations, and surface characterization and long-term stability were studied using Dynamic Light Scattering (DLS). The best formulation was chosen for further surface characterization, including Transmission Electron Microscopy (TEM), Differential Scanning Calorimetry (DSC), and Fouriertransform infrared (FTIR) spectroscopy. Moreover, entrapment efficiency percentage (EE%), drug release, skin penetration, cytotoxicity on B16F10 melanoma cells, effect on melanin production, and anti- tyrosinase activity were tested for the selected formulation.

RESULTS

Based on HPLC results, FEG contained 34.501 mg/g of Glab, and FEL contained 31.714 mg/g of LQ. Among 20 different formulations, NLC 20 (LG-NLCs) showed desirable DLS results with a Z-average size of 185.3 ± 1.08 nm, polydispersity index (PDI) of 0.229 ± 0.35, and zeta potential of -16.2 ± 1.13 mV. It indicated good spherical shape, high EE% (79.01% for Glab and 69.27% for LQ), two-stage release pattern (an initial burst release followed by sustained release), efficient skin penetration, and strong anti-tyrosinase activity. LG-NLCs had acceptable physiochemical stability for up to 9 months and were non-cytotoxic.

CONCLUSION

The LG-NLC formulation has revealed desirable surface characterization, good physiochemical stability, efficient drug release pattern and penetration, and high EE%. Therefore, it can be a suitable nanosystem for the delivery of licorice extract in the treatment of hyperpigmentation.