Although carnosic acid (CaA) is known as one of the useful polyphenolic compounds due to its antimicrobial and antioxidant activities, it is limited to use as aqueous solution because of its low solubility and unstability. The objective of this study was to investigate the capability of CA to improve the solubility of CaA by forming an inclusion complex in comparison with cyclodextrin (CD) and maltodextrin (MD). Enzymatically-produced CA was reacted with CaA in aqueous solution to form a complex using a freeze-drying. And the formation of complex between CaA and CA was identified by X-ray diffraction (XRD), differential scanning calorimeter (DSC) and field emission scanning electron microscope (FESEM). As a result of XRD and DSC analysis, disappearance of characteristics of CaA that was reacted with CA could be indicated the complex formation between CaA and CA. The formation complex of CaA with CA was also confirmed through the change in morphology of CaA and CA in the electron micrograph result. Aqueous solubility of CaA with various concentrations (1, 5, 10, 20, 30%) of CA was measured by absorbance change at 285 nm. As a result, the solubility of the CaA was significantly increased with increasing CA concentration. At 30% CA, the maximum solubility of CaA was 0.095% (w/v) in solution, which was approximately 3 times higher than that of free CaA (0.033%). The effect of inclusion complex with CA on the solubility of CaA was superior than that with CD (0.057%) and MD (0.066%). These results indicated that the effects on the solubility and formation abilities of inclusion complex were associated with host materials and its concentration rate. This study confirmed that the CA can be a viable solution to improve the aqueous solubility of CaA. Further investigation is still needed to understand the effect of inclusion complex with CA.

• Jiwoon Park(Department of Biosystems and Biomaterials Science and Engineering, Seoul National University)
• Shin-Joung Rho(Center for Food and Bioconvergence, Seoul National University)
• Yong-Ro Kim(Department of Biosystems and Biomaterials Science and Engineering, Seoul National University Center for Food and Bioconvergence, Seoul National University)