Multiple antibiotic-resistant Helicobacter pylori (H. pylori), one of the major causes of gastric cancer, is now increasingly reported. The aim of this study was to screen medicinal plants widely used in Thailand as possible sources of medicines that can be used to treat H. pylori infection. Twenty-four extracts from 13 kinds of Thai herbs were tested for their antibacterial activity against 20 strains of antibiotic-resistant H. pylori. Inhibition of growth was tested by the paper disc agar diffusion method. Most strains of H. pylori examined were proved to be susceptible to seven medicinal plants; i.e., Peltophorum pterocarpum, Piper betle, Punica granatum (P. granatum), Quercus infectoria (Q. infectoria), Tamarindus indica, Uncaria gambir, and Walsura robusta. Among these extracts, P. granatum and Q. infectoria exhibited the greatest inhibitory potencies. Minimal inhibitory concentrations (MIC) were determined by the agar dilution method in Petri dishes with a Millipore filter membrane, and minimal bactericidal concentrations (MBC) were assessed with the extract that gave a significant MIC value against each bacterial strain by placing the Millipore filter membrane onto a fresh Isosensitest agar plate. Ethanolic extracts of P. granatum and Q. infectoria significantly reduced the growth of all strains of H. pylori, with the best MIC values at 0.8 and 3.1 mg/ml, and the best MBC values at 3.1 and 6.2 mg/ml, respectively. Effective fractions partially purified from both plant species yielded MICs and MBCs that were at least 10-fold less compared with the crude extracts. From the data obtained, it is hoped that P. granatum and Q. infectoria will become useful sources with which to develop new therapeutic agents for H. pylori infection.
2008 by The Pharmaceutical Society of Japan