In vitro Susceptibility of Helicobacter pylori to Licorice Extract

Helicobacter pylori is the causative agent of gastritis and peptic ulcer disease. Eradication of H. pylori is hard to achieve and often require multiple antibiotics regimens. These regimens are quite expensive and have substantial side effects. Licorice is a traditional drug which is frequently used for gastric discomforts in Iran. The susceptibility of H. pylori to the extract of licorice has been investigated in the present study.

One hundred and eighty clinical H. pylori strains were isolated in this study. For comparison and control, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa were also included in this study. Agar dilution assay was used to test the susceptibility of the clinical isolates of H. pylori to the Glycyrrhiza extract at different concentration. The assay plates had 25, 50, 100, 150, 200, 300 and 400 mg/ml of licorice extract.

Licorice extract inhibited the H. pylori strains with a MIC range of 50-400 mg/ml. The present results show that therapeutically administered concentrations of licorice extract could have growth-inhibiting effect on H. pylori in vitro.

The above preliminary experiments indicated strongly that licorice extract has some anti-H. pylori property and H. pylori shows susceptibility to licorice extract in concentration ranges that are achievable in the stomach. The resistance of other bacterial species indicates the possibility of selective therapy without adverse effects on the normal bacterial flora.