Anti-Helicobacter pylori activity of some newly synthesized derivatives of xanthone.

A series of 20 xanthone derivatives was synthesized and evaluated for anti-Helicobacter pylori (H. pylori) activity. Qualitative and quantitative in vitro tests using the Kirby-Bauer method (agar disc-diffusion method) were performed. The tested compounds were screened against clarithromycin- and/or metronidazole-resistant strains of H. pylori. As a reference, Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacterial strains were examined. On the basis of microbiological assays, xanthones can be considered as potential anti-H. pylori agents. They displayed significant activity against the examined strains, which was higher against the bacteria resistant to metronidazole than clarithromycin. The lowest MIC values ranging up to 20 mg l-1 were observed for the following compounds: 3, 4, 8, 9, 12, 19 (against the metronidazole-resistant strains) and the compound 10 (against the clarithromycin-resistant strain). These preliminary results for screening of xanthone derivatives form a part of an ongoing study of the structure-activity relationships of a large group of compounds. Microbiological assays will be conducted afterwards to determine the mechanism of xanthones' action against H. pylori.