Anti-Helicobacter pylori (H. pylori) effects of aminoreductone (AR), a Maillard reaction product, were evaluated in this study. AR effectively inhibited the growth of all 24 strains (19 clinical isolates and 5 isogenic mutants) irrespective of susceptibility to antibiotics and clinical manifestation. The minimum inhibitory concentration (MIC) of AR ranged from 0.5 to 5 mM. A killing assay with multiples of MIC was performed, demonstrating that the killing activity of AR was significantly higher than that of its derived melanoidin, an inhibitor of H. pylori urease-gastric mucin adherence, formed in the final stage of the Maillard reaction. These significant effects of AR on H. pylori were observed even in acidic conditions (pH 3). At most, 25 mM AR effectively exhibited bactericidal activity in all strains. These results rise up the possibility that foods containing AR, such as milk and dairy products, are valuable sources for preventing colonization of H. pylori in the stomach and its associated tissue damages.

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In this study, antimicrobial activity of aminoreductone (AR), a product formed during the initial stage of the Maillard reaction, against methicillin-resistant Staphylococcus aureus (MRSA) was evaluated. The significant growth inhibition of all 51 MRSA isolates irrespective of drug susceptibility by AR was observed. The minimum inhibitory concentration (MIC) of AR ranged from 13 to 26 mM. The bactericidal activity of AR was evaluated by a killing assay with multiples of MIC, and it was recognized to depend on its dose. The combined effects of AR and antibiotics frequently used for the treatment of infections caused by Gram-positive and Gram-negative bacteria, such as amikacin (AN), ciprofloxacin, imipenem and levofloxacin, were examined. As a result, AR did not interfere with these antibiotic activities against 12 MRSA isolates selected and showed the advanced effect of growth inhibition in combination with antibiotics. Moreover, the inhibitory effects of AR were similar to those of AN, an antibiotic with known adverse effects, some serious. These findings show that AR is a naturally formed antimicrobial agent present in thermally processed foods with potential health benefits in medical practice.

The anti-Helicobacter pylori (H. pylori) activity of a water extract of Chinese chive (Allium tuberosum) (WCC) was investigated. On disk diffusion assay, WCC effectively inhibited the growth of all 21 strains tested, including isogenic mutants, showing inhibition diameters of 12 to 29 mm, irrespective of drug susceptibility and clinical manifestation. The minimum inhibitory concentration (MIC) of WCC was 2.45 mg dry weight/mL. Killing assay with multiples of MIC confirmed that WCC had bactericidal activity and that the inhibitory effects were dose dependent. In addition, to determine whether the inhibitory activity of WCC under severe stress conditions, such as heat and acidity, is altered, the stability of WCC was evaluated. The inhibitory activity of WCC exposed to acidic conditions (pH 1.0 to 6.4) was stable, while heat-treated WCC (100℃, 10 min) showed slightly decreased inhibition activity. On combination assay with antibiotics frequently used in clinical practice, WCC was found to be an innocuous agent for antibiotic activity. These results suggest that daily intake of WCC is able to prevent H. pylori colonization in the stomach, and that it could be applied as adjuvant therapy in H. pylori eradication.Keywords: Helicobacter pylori, Chinese chive, Allium tuberosum, antibiotic resistance, growth inhibition effect, bactericidal activity * To whom correspondence should be addressed. *E-mail: htake@kochi-u.ac.jp (H. Takeuchi) tomokos@kochi-u.ac.jp (T. Shimamura) IntroductionHelicobacter pylori (H. pylori) was recognized as a human carcinogen by IARC in 1994(Sugiyama et al., 2002, and is a pathogenic gram-negative spiral microaerophilic bacterium that colonizes the human stomach in up to half the world's population (Rothenbacher and Brenner, 2003). H. pylori plays a major role in the development of gastro-duodenal diseases, including gastritis, peptic ulcer and gastric cancer, and is associated with a wide range of non-gastrointestinal tract conditions such as idiopathic thrombocytopenic purpura. As gastric cancer is one of the most frequent causes of cancer-related death, eradication of H. pylori can, therefore, contribute to the treatment and prevention of these diseases. Generally, H. pylori infection in clinical practice is treated with an effective regimen, a triple therapy consisting of a proton pump inhibitor and combinations of two antibiotics; amoxicillin (AMPC) and clarithromycin (CAM) or AMPC and metronidazole (MNZ) in Japan (Nishimori, et al., 2006). However, unsuccessful eradication therapy is increasing due to the increased occurrence of drug-resistant H. pylori (Nariman, et al., 2004). The appearance rates of drug-resistant H. pylori against AMPC, CAM and MNZ from 2007to 2009 were 0.4%, 19.4% and 25.7%, respectively (Lyudmila et al., 2010, and these rates are continuing to escalate.Instead of antibiotics, non-antibiotic substances derived from foods with anti-H. pylori activity are now a focus in Gastroenterology. There have been several reports on natural compounds derived from foods, includin...

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