Anti-Helicobacter pylori Compounds of Sambucus williamsii Hance Branch

Sambucus williamsii Hance (Viburnaceae), the Korean elderberry, is widely used in herbal medicine and in the food industry. It is known to have various pharmacological effects, including antitumor, antioxidant, anti-inflammatory, and antimicrobial activities. During our search for anti-Helicobacter pylori compounds from natural resources, the methanol extract of the S. williamsii branch significantly inhibited the growth of H. pylori. Three phenolic and four lignan compounds were isolated from the methylene chloride fraction that had shown the most potent anti-H. pylori activity among the hexane, methylene chloride, ethyl acetate, butanol, and water fractions. The chemical structures were identified to be three phenolics of sylvopinol (1), dihydroconiferyl alcohol (2), and (7S,8R)-guaiacylglycerol (3) and four lignans of boehmenan (4), (7S,8S)-guaiacylglycerol β-coniferyl ether (6) and lawsonicin (7) with a new lignan, (7R,8R)-sambucanol (5), the structure of which was established by ¹H- and ¹³C-NMR, and HRESI-MS, as well as quantum chemical electronic circular dichroism (ECD) calculations. Among the isolates, compounds 3 and 4 exhibited significant anti-H. pylori activity against strains 51 and 26695. Compound 3 displayed more potent antibacterial activity with MIC values of 3.13 and 6.25 μM, and MIC₅₀ values of 28.5 and 56.8 μM against the two strains, respectively. Their inhibitory activities were higher than those of a positive control, quercetin. Furthermore, these two compounds showed moderate urease inhibitory activity. A molecular docking simulation revealed the high binding ability of 3 and 4 to the active site of H. pylori urease. These results will provide further insights into the design of more potent natural products for eradicating H. pylori.