Inhibitory Effect of Partially Purified Compounds from Pomegranate Peel and Licorice Extracts on Growth and Urease Activity of Helicobacter pylori

Helicobacter pylori (H.pylori) is the main causative agent responsible for chronic gastritis, peptic ulcer, and gastric cancer in humans.An important virulence factor of H. pylori is urease that converts urea into ammonia, producing a neutral microenvironment, which allows colonization and survival in the stomach lining.Although various therapies have been introduced for the treatment of H. pylori infection, the eradication failure rate stays as high as 5-20% along with frequent recurrence of gastric ulcers even after complete healing.Looking for an alternative mode of treatment using natural products, we investigated the effects of pomegranate peel and licorice extracts that had been fractioned using ethyl acetate and methanol into 4 fractions (F1-F4) on the growth (disc diffusion and minimum inhibitory concentration -MIC) and urease activity of this pathogen.We found that all fractions had antimicrobial activity with the maximum activity observed with the F1 fraction of both pomegranate peel and licorice extracts with growth inhibitory zones of 33 mm and 26 mm, and MICs of 2 and 1 mg/ml, respectively.The F2 and F4 fractions of licorice extract, and F3 of pomegranate peel extract showed MIC values of 4 mg/mL, whereas the F4 fraction of pomegranate peel extract and F3 of licorice extract showed MIC values of 8 mg/ml.The F1 and F2 fractions of pomegranate peel caused 80 and 91% inhibition of urease activity and the F1 fraction of licorice caused total inhibition (100%) of H. pylori urease activity at MIC values.In conclusion, these results indicate that both pomegranate and licorice contain important bioactive compounds against H. pylori and should be examined further to help in the fight against this important pathogen.