Comparative evaluation of the activity of plant infusions against Helicobacter pylori strains by three methods

The aim of the study was to assess the activities of six plant infusions against Helicobacter pylori strains using a comparative screening assay (CSA), agar-well diffusion method (AWDM) and microscopy. Green tea, St John's wort (SJW), rooibos, peppermint, chamomile and lime flower aqueous infusion concentrations were chosen to mimic those in herbal teas/tisanes. CSA concentrations were 4.5 mg ml⁻¹ for chamomile and 6.8 mg ml⁻¹ for the other agents. AWDM amounts were 0.4 mg/well for the chamomile and 0.6 mg/well for the other agents. Using CSA, ≥8 × 10⁴ colony forming unit reduction was found in >60 % of the strains by the green tea (81.5 %), SJW (75.9 %) and rooibos (63.0 %) within 2 h. Similarly, by AWDM, the activity against >60 % of the strains was found by the green tea, SJW and rooibos. Gram staining results were alike, showing mostly/only coccoids in >66 % of the strains by the same three agents within 2 h. Lime flowers showed the lowest activity by all methods. In conclusion, CSA allows comparing the activities of many agents against numerous strains. To our knowledge, these are the first data about rooibos and lime flower activities against H. pylori. All the three methods revealed that the most active agents were the green tea, SJW and rooibos, which also possess additional beneficial properties, e.g. antioxidant, anti-inflammatory and antitumor effects, therefore these plants may have a beneficial use as prophylactic agents against or adjuvants in the therapy of H. pylori infection.