Improvement of Dissolution Properties of a New Helicobacter pylori Eradicating Agent (TG44) by Inclusion Complexation with β-Cyclodextrin

Kinsei Anzai, Jun-ichi Mizoguchi, Toshiharu Yanagi, Fumitoshi Hirayama, Hidetoshi Arima, Kaneto Uekama
2007 Chemical and pharmaceutical bulletin  
Helicobacter pylori (H. pylori) is implicated in the etiology of duodenal and gastric ulcer diseases and gastric cancer in severe cases. 1) Many studies have been demonstrated that H. pylori eradication treatment is indicated in all patients with active or recurrent peptic ulceration. Oral triple-therapy schedules using a proton inhibitor or an H 2 -antagonist in combination of two antibiotics such as clarithromycin, metronidazole, amoxicillin and tetracycline have been proved to be highly
more » ... tive in the treatment of H. pylori. However, such the triple therapy sometimes results in failure of the H. pylori therapy because of poor compliance with the treatment regimen, with the development of antibiotic resistance and with drug-drug interaction, etc. 2,3) Therefore, it is desired to develop new strategies of H. pylori therapy, including the development of new drugs and multiple-combinations, etc. 4-Methylbenzyl-4Ј-[trans-4-(guanidinomethyl)cyclohexylcarbonyloxy]biphenyl-4-carboxlylate monohydrochloride (TG44, Fig. 4 for the chemical structure) is a newly synthesized H. pylori eradicating agent with high selectivity to H. pylori, compared with other gram-negative and gram-positive bacteria. 4) The structure of TG44 is closely related to an antiulcer agent, benexate, which is formulated in the form of b-CyD complex and on market as a trade name of Ulgut or Lonmiel, although the pharmacological indication is different between them. Because benezate is commercially available as a b-CyD complex, we used b-CyD as a solubilizing agent for TG44, among various CyDs and their derivatives. The H. pylori eradicating activity of TG44 was markedly en-hanced when it was orally administered in the form of b-CyD complex, compared with TG44 alone, which will be reported elsewhere. The enhanced antimicrobial activity of TG44/b-CyD complex may be ascribed to improved dissolving properties of the b-CyD complex, but the detailed mechanism is not yet fully elucidated. This study dealt with the inclusion complexation of TG44 with b-CyD in water and in solid state, to gain insight into the high in-vivo H. pylori eradicating activity of TG44/b-CyD complex. Experimental Materials TG44 and b-CyD were supplied by Nagase ChemteX Corporation (Osaka, Japan) and Nihon Shokuhin Kako Co., Ltd. (Tokyo, Japan), respectively. All other chemicals and solvents were of analytical reagent grade, and deionized distilled water was used throughout the study. Solubility Measurements Solubility studies were carried out according to the method of Higuchi and Connors. 5) The screw-capped vials containing TG44 in excess amounts (0.3 g/50 ml) in aqueous CyD solutions at various concentrations (2ϫ10 Ϫ3 -8ϫ10 Ϫ3 M) were stirred for 24 h at 25°C. The suspension was filtered through a syringe with a membrane-filter, and the filtrate was adequately diluted and analyzed for TG44 using high-performance liquid chromatography (HPLC) under the following conditions: a Shimadzu Class LC-10A HPLC system, (Kyoto, Japan), a column of CERI L-column ODS 5 mm (Tokyo, Japan), a mobile phase of phosphate buffer (pHϭ3) of H 2 O/acetonitrile (1 : 1 v/v), a flow rate of 1.0 ml/min, and a detection of 278 nm. The 1 : 1 apparent stability constant (Kc, M Ϫ1 ) of TG44/b-CyD complex was calculated from the initial straight line portion of the phase solubility diagram according to the equation of Kcϭslope/[So(1-slope)], where So is the intrinsic solubility of TG44. 5) Spectroscopic Studies Ultraviolet (UV) and fluorescence spectra of TG44 in the absence and presence of b-CyD (7.6ϫ10 Ϫ4 -3.8ϫ10 Ϫ3 M) in water were recorded with Shimadzu UV-2500PC (Kyoto, Japan) and Shi-The interaction of a newly developed Helicobacter pylori eradicating agent (TG44, 4-methylbenzyl-4-[trans-4-(guanidinomethyl)cyclohexylcarbonyloxy]biphenyl-4-carboxlylate monohydrochloride) with b b-cyclodextrin (b b-CyD) in aqueous solution and in solid state was studied to gain insight into the high in-vivo H. pylori eradicating activity of TG44/b b-CyD complex. The interaction was studied by the solubility method, spectroscopic methods, powder X-ray diffractometry and differential scanning colorimetry (DSC). TG44 gave A L -type phase solubility diagram with b b-CyD in water, showing a linear increase in solubility of the drug up to 8 mM b b-CyD concentration. The solubility of TG44 (0.04 mM in water at 25°C) increased about 70-folds at 8 mM b b-CyD. Ultraviolet, circular dichroism, fluorescence and 1 H-nuclear magnetic resonance spectroscopic studies indicated that TG44 forms the inclusion complex with b b-CyD in a 1 : 1 stoichiometry and the biphenyl moiety of TG44 is preferably included in the b b-CyD cavity in water. The Giordano plot made by monitoring changes in the fusion enthalpy of TG44 (about 184°C) suggested that TG44 forms the 1 : 1 complex with b b-CyD in the solid state. The TG44/b b- CyD solid complex in a 1 : 1 stoichiometry was prepared by the grinding and spray-drying methods and confirmed by powder X-ray diffractometry and DSC that the complex is in an amorphous state. The initial dissolution rate of TG44/b b-CyD complex was significantly faster than those of the drug alone and the physical mixture of both components, maintaining higher supersaturated concentrations of the drug for a long time. The results suggested that the higher eradicating activity of TG44/b b-CyD complex to Helicobacter pylori, compared with that of the drug alone, is attributable at least partly to the faster dissolving property of the complex and its ability to maintain the supersaturated state of the drug in the gastric fluid.
doi:10.1248/cpb.55.1466 pmid:17917290 fatcat:psvlzfxbunebxne3r4sdccapgy