A glabridin is an active ingredient in the root extract of licorice (Glycyrrhiza glabra) and brownish powder. It is an isoflavane, part of plant-derived molecules, the natural phenols. Glabridin is insoluble in water and oil, but soluble in organic solvents such as propylene glycol. Glabridin is known for properties such as skin whitening, anti-inflammatory, cell-protective abilities and antioxidant. The stability of glabridin is greatly affected by various environmental factors such as pH, temperature, light, heat, and oxygen. It is also known to reduce absorption in vivo because it conferred low polarity and water solubility. This makes it difficult to apply glabridin in cosmetic formulations. Gamma-cyclodextrins are widely applied in various fields such as food, pharmaceutics, and cosmetics. They are bio-friendly and could encapsulate the hydrophobic component which is unstable in external environment. Gamma-cyclodextrin based metal-organic frameworks (COFs) are formed by gamma-cyclodextrin as a organic ligand and potassium ion as a inorganic metal center. COFs have the various properties such as biodegradable, highly porosity, large surface areas, and non-toxicity. In this study, COFs encapsulated glabridin was synthesized to stabilize the glabridin in the external environment and increase the solubility in water. The characters of COFs encapsulated the glabridin were investigated with scanning electron microscope (SEM), X-ray diffraction (XRD), nuclear magnetic resonance (NMR), fourier-transform infrared spectroscopy (FT-IR), and UV spectrometer. Then, the water solubility was evaluated and the stability of COFs encapsulated glabridin was confirmed by high-performance liquid chromatography (HPLC) measurement for 6 months.

The COFs encapsulated the glabridin were successfully synthesized. The shapes of COFs were similar cubic crystals and the COFs crystalline was maintained after encapsulating the glabridin. The encapsulated glabridin peak was confirmed with NMR data. In this study, porosity COFs were used as encapsulated glabridin carrier. It could conclude that the COFs encapsulated the glabridin was successfully synthesized and had high stability from the external environment and solubility in water. The synthesized COFs could apply for various fields such as drug delivery, food, and cosmetics.