Chemical Investigation of Fruits and Their Antibacterial Activity against .

The fruit of , known as 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 fruits against . However, so far, the antibacterial activity of fruits and antibacterial components against has not been investigated despite the traditional folk use. The current study was conducted to investigate the bioactive chemical components of fruits and evaluate their antibacterial activity against . Phytochemical investigation of the EtOH extract of fruits led to the isolation and identification of nine compounds (-), including phellolactone (), 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 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- activity test, compound showed the most potent antibacterial activity against strain 51, with 94.4% inhibition (MIC and MIC values of 22 and 50 μM, respectively), comparable to that of metronidazole (97.0% inhibition, and MIC and MIC values of 17 and 46 μM, respectively). Moreover, compound exhibited moderate antibacterial activity against strain 51, with 58.6% inhibition (MIC value of 99 μM), 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- activity. Conclusion: These findings demonstrated that fruits had antibacterial activity against and could be used in the treatment of gastric and duodenal ulcers. Meanwhile, the active compound, 1-methyl-2-(8)-8-tridecenyl-4(1)-quinolinone (), identified herein also indicated the potential application in the development of novel antibiotics against .