title: Clove oil prevents glycyrrhizin gel formation in aqueous solution.
abstract: One persistent problem with using therapeutic concentrations of glycyrrhizin (GZ) is that, at these high concentrations, it forms a gel in an aqueous solution. We previously solved this problem by dissolving GZ in a highly concentrated phosphate buffer. Unfortunately, the resulting GZ solution has a hyperosmotic pressure that renders it unsuitable for use in patients. The aim of this study was to prepare a highly concentrated GZ solution having an osmotic pressure ratio of 1 and a pH of 7.4. By adding small amounts of oil and using a 100 mM phosphate buffer, we achieved an emulsified GZ solution that is stable at room temperature and has a physiological osmotic pressure and pH. When clove oil was used as an emulsifier, the gel formation temperature of GZ solution decreased appreciably compared to that of GZ solution without clove oil. Using scanning electron microscopy (SEM), we examined the detailed characteristics of GZ gels prepared from solutions with or without clove oil. SEM of cross sections of GZ gels revealed an irregular structure in gels prepared with clove oil, indicating that clove oil prevented the formation of the intermolecular GZ networks typically characterized by gels derived from pure GZ solutions.
authors.affiliation: Department of Pharmaceutics, Faculty of Pharmaceutical Sciences, Hokuriku University, Ho-3, Kanagawa-machi, Kanasawa, Japan. k-koga@hokuriku-u.ac.jp
authors.forename: Kenjiro
authors.initials: K
authors.lastname: Koga
authors.forename: Kumiko
authors.initials: K
authors.lastname: Takekoshi
authors.forename: Susumu
authors.initials: S
authors.lastname: Kawashima
authors.forename: Masakazu
authors.initials: M
authors.lastname: Taniguchi
authors.forename: Masahiro
authors.initials: M
authors.lastname: Murakami
mesh_terms: D002851:Chromatography, High Pressure Liquid; D045783:Clove Oil / Q000737:chemistry*; D005612:Freeze Drying; D005782:Gels; D019695:Glycyrrhizic Acid / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D009994:Osmolar Concentration; D010316:Particle Size; D012996:Solutions; D013696:Temperature
chemical_list: D045783:Clove Oil; D005782:Gels; D012996:Solutions; D019695:Glycyrrhizic Acid