In vitro activity of artemisone and artemisinin derivatives against extracellular and intracellular Helicobacter pylori

The in vitro activity of the new artemisinin derivative artemisone as well as other molecules of the same class against Helicobacter pylori and their effects when combined with standard antibiotics were evaluated. Since H. pylori can be internalised into gastric epithelial cells, the effects of artemisinin, dihydroartemisinin and artemisone against intracellular H. pylori were also investigated. Bacteriostatic [minimum inhibitory concentration (MIC)] and bactericidal [minimum bactericidal concentration (MBC)] activities were assessed against 24 clinical strains of H. pylori with different antibiotics susceptibilities. Artemisone showed MIC₅₀ and MIC₉₀ values of 0.25 mg/L and 0.5 mg/L, respectively, and an MBC₅₀ value of 0.5 mg/L. Artemisone was synergistic with amoxicillin in 60% of strains, with clarithromycin in 40% and with metronidazole in 20%. There was no interaction between artemisone and omeprazole or bismuth citrate. Against intracellular H. pylori, only dihydroartemisinin at 2× MIC caused a 1 log₁₀ CFU decrease after 18 h and 24 h of incubation. This is the first demonstration in vitro of the activity of artemisinin derivatives against intracellular H. pylori and indicates that artemisone has the potential to be efficacious for the treatment of H. pylori infection, especially in combination with antibiotics.