Stabilization of glabridin by chitosan nano-complex

Abstract

Stabilization of glabridin, an isoflavan extracted from Glycyrrhiza glabra (licorice) root, was investigated in electrostatic complex prepared by glabridin and chitosan. Nanoparticles of the complex were spontaneously formed by adding glabridin into chitosan or three N-acylated chitosans which were synthesized by reacting chitosan with acid anhydride. N-acylated chitosans were characterized by Fourier transform infrared spectroscopy (FT-IR) and 1H-NMR. Degrees of N-acyl substitution of N-propionic, Nbutanoic, and N-hexanoic chitosan were 28.2, 34.74, and 35.02%, respectively. Transmission electron microscopy (TEM) showed the morphology of the complex particles was nano-scale spherical shape, and average size of the particles estimated by particle analyzer was between 32 and 42 nm. The electrostatic interaction between amino group of chitosan and hydroxyl group of glabridin was confirmed by the semi-doublet peak at 1590 nm−1 in FT-IR spectra. Maximum encapsulation efficiency of glabridin was found to be 84% when N-propionic chitosan with 1% glabridin was used for the preparation of nanoparticles, and the efficiency decreased upon increasing glabridin concentration. Stability of glabridin under UV-ray was enhanced after the complex formation with chitosan, and the enhancement was further augmented when Nacylated chitosan was used instead of chitosan. Long-term stability of glabridin in aqueous solution was also affected by the complex formation, and 2.2-fold stability enhancement at 25°C after 7-day incubation was observed in the case of N-hexanoyl chitosan. Chitosan or its derivatives could be used for the stabilization of polyphenolic compound such as glabridin and applied for the development of functional cosmetic products with skin-whitening effect.