Glabridin is a prenylated isoflavane originally isolated from the roots of Glycyrrhiza glabra L. (Favaceae), commonly known as licorice (Mitscher, Park, & Clark, 1980; Shibata, 2000). A number of biological activities of glabridin have been reported, including antioxidation (Belinky, Aviram, Fuhrman, Rosenblat, & Vaya, 1998; Fukai, Satoh, Nomura, & Sakagami, 2003), inhibiting melanogenesis (Nerya et al., 2003; Yokota, Nishio, Kubota, & Mizoguchi, 1998), anti-inflammatory (Yehuda, Madar, Leikin-Frenkel, & Tamir, 2015), estrogen and antiproliferative activity in human breast cancer cells (Simons, Gruppen, Bovee, Verbruggen, & Vincken, 2012; Tamir et al., 2000) and enhancing memory (Yu et al., 2008). Moreover, Yokota et al. (1998) found that glabridin inhibited tyrosinase activity in B16 murine melanoma cells at concentration between 0.1 to 1.0 μg/ml and had no detectable effect on their DNA synthesis. Numerous patents are dedicated to the application and formulation of Glab for cosmetic or dermatologic outcomes (Niu et al., 2015, Zhang, 2015). However, its low polarity and poor water solubility lowered its absorption in vivo, resulting in low bioavailability and limited clinical application (Ao et al., 2010). Several preparation methods have been designed to improve the stability and solubility of glabridin, such as nanoemulsion (Hsieh, Li, Lu, & Wang, 2012) and chitosan nanoparticle (Park, Park, & Lee, 2012). These methods have been showed to enhance the stability of glabridin, however, the effect of preparation on the bioactivity properties of glabridin was not specified in those reports.

We introduced a novel inclusion complex of glabridin and HP-β-CD that features improved aqueous solubility and bioactivity. The solubility of glabridin/HP-β-CD inclusion complex in pure water was examined. In addition, the DPPH radical-scavenging capacity and tyrosinase inhibitory activity of the inclusion complex were tested.