Anti-Helicobacter pylori activity of swertianolin, isolated from swertia herb

Helicobacter pylori is a Gram-negative, spiral-shaped, motile bacterium present in human stomachs that causes gastric ulcers. A preliminary screening revealed that a methanolic extract of swertia herb demonstrated anti-H. pylori activity. Swertia herb (Swertia japonica Makino, Gentianaceae) is a well-known Japanese traditional medicine to treat gastrointestinal diseases. In this study, we explored the active compounds in methanolic extract of swertia herb. The dried extract was dissolved in water and partitioned with n-hexane, ethyl acetate, and n-butanol, successively. The part soluble in ethyl acetate showed effective anti-H. pylori activity, and two compounds, swertianolin (1) and isoorientin (2), were isolated. The IC₅₀ values of 1, 2, and amoxicillin (AMPC) which is used as positive control were 6.1, 177.0, and 0.044 μM, respectively. The minimum bactericidal concentration (MBC) values of 1 and AMPC were 91.7 and 0.21 μM, respectively. The MBC of 2 could not be determined (> 892.9 μM). Furthermore, synergy was observed when compound 1 was used in combination with AMCP. Therefore, 1 could be considered as one of the active compounds of swertia herb. To our knowledge, the anti-H. pylori activities of methanolic extract of swertia herb and its isolated compound have never been reported.