Anti-<i>Helicobacter pylori</i> Activity of Six Major Compounds Isolated from <i>Rumex acetosa</i>

Abstract

Gastric problems are often caused by the well-known <i>Helicobacter pylori</i> (<i>H. pylori</i>) bacterium. One of the biggest obstacles to the treatment of <i>H. pylori</i> infections is increasing the antibiotic resistance. During our search for naturally derived anti-<i>H. pylori</i> compounds, six major compounds were isolated from the methylene chloride (CH₂Cl₂) and ethyl acetate (EtOAc) fractions of <i>Rumex acetos</i>a that showed anti-<i>H. pylori</i> activity. Three anthraquinones and three anthraquinone glucosides were identified as the major chemical constituents of the CH₂Cl₂ and EtOAc fractions, respectively. The chemical structures were identified to be emodin (<b>1</b>), chrysophanol (<b>2</b>), physcion (<b>3</b>), emodin-8-<i>O</i>-β-d-glucoside (<b>4</b>), chrysophanol-8-<i>O</i>-β-d-glucoside (<b>5</b>), and physcion-8-<i>O</i>-β-d-glucoside (<b>6</b>) by UV, ¹H NMR, ¹³C NMR, and mass spectrometry. Anti-<i>H. pylori</i> activity, including the minimum inhibitory concentration (MIC) value of each compound, was evaluated against two <i>H. pylori</i> strains. All isolates exhibited anti-<i>H. pylori</i> activity with different potencies, with an MIC value ranging between 3.13 and 25 μM. However, some variations were found between the two strains. While compound <b>5</b> displayed the most potent antibacterial activity with an MIC₅₀ value of 8.60 μM and an MIC₉₀ value of 15.7 μM against <i>H. pylori</i> strain 51, compound <b>1</b> exhibited the most potent inhibitory activity against <i>H. pylori</i> strain 43504. The two compounds also showed moderate urease inhibitory activity, with compound <b>1</b> demonstrating activity higher than that of compound <b>5</b>. Furthermore, a molecular docking study revealed the high binding ability of compounds <b>1</b> and <b>5</b> to the active site of <i>H. pylori</i> urease. The present study suggests that the six anthraquinones isolated from <i>R. acetosa</i> with the whole parts of this plant may be natural candidates for the treatment of <i>H. pylori</i> infection. Further studies are required to determine the exact mechanism of action and to evaluate safety issues in the human body.