Chemical Investigation of Tetradium ruticarpum Fruits and Their Antibacterial Activity against Helicobacter pylori

Abstract

The fruit of Tetradium ruticarpum, known as Evodiae Fructus, is a traditional herbal medicine used to treat gastric and duodenal ulcers, vomiting, and diarrhea. The traditional usage can be potentially associated with the antibacterial activity of T. ruticarpum fruits against Helicobacter pylori. However, so far, the antibacterial activity of T. ruticarpum fruits and antibacterial components against H. pylori has not been investigated despite the traditional folk use. The current study was conducted to investigate the bioactive chemical components of T. ruticarpum fruits and evaluate their antibacterial activity against H. pylori. Phytochemical investigation of the EtOH extract of T. ruticarpum fruits led to the isolation and identification of nine compounds (1-9), including phellolactone (1), the absolute configuration of which has not yet been determined. The chemical structures of the isolated compounds were elucidated by analyzing the spectroscopic data from one-dimensional (1D) and two-dimensional (2D) NMR and high-resolution electrospray ionization mass spectrometry (HR-ESIMS) experiments. Specifically, the absolute configuration of compound 1 was established by the application of computational methods, including electronic circular dichroism (ECD) calculation and the NOE/ROE-based interproton distance measurement technique via peak amplitude normalization for the improved cross-relaxation (PANIC) method. In the anti-H. pylori activity test, compound 3 showed the most potent antibacterial activity against H. pylori strain 51, with 94.4% inhibition (MIC50 and MIC90 values of 22 and 50 mu M, respectively), comparable to that of metronidazole (97.0% inhibition, and MIC50 and MIC90 values of 17 and 46 mu M, respectively). Moreover, compound 5 exhibited moderate antibacterial activity against H. pylori strain 51, with 58.6% inhibition (MIC50 value of 99 mu M), which was higher than that of quercetin (34.4% inhibition) as a positive control. Based on the bioactivity results, we also analyzed the structure- activity relationship of the anti-H. pylori activity. Conclusion: These findings demonstrated that T. ruticarpum fruits had antibacterial activity against H. pylori and could be used in the treatment of gastric and duodenal ulcers. Meanwhile, the active compound, 1methyl-2-(8E)-8-tridecenyl-4(1H)-quinolinone (3), identified herein also indicated the potential application in the development of novel antibiotics against H. pylori .