Chiang Mai Journal of Science

 The aqueous extracts of Camellia sinensis leaf including green tea, oolong tea and black tea, and sixteen medicinal plants were evaluated for their effects on growth of Helicobacter pylori. Phytochemical compounds; phenolic and tea catechins, were identified in different types of tea leaf extract. Green tea leaf extract revealed a high amount of tea catechins such as epigallocatechin gallate, epicatechins, caffeine and gallic acid. In addition, oolong tea contained high amounts of epigallocatechins and catechins. Moreover, all plant extracts demonstrated the phenolic compounds and several phytochemical groups; simple phenol, phenolic acids and flavonols. Green tea leaf extract showed the highest phenolic content at a value of 315.09 ± 10.16 mg GAE/g extract and the greatest antioxidant activity in inhibiting DPPH radicals by 170.51 ± 3.68 mg GAE/g extract. Extracts of tea leaves and medicinal plants especially Aegle marmelos and Terminalia catappa could inhibit the standard strain, H. pylori DMST20165 and two isolates of H. pylori; No. 31 and 36. The greatest anti-H. pylori activity was observed in the green tea extract at a minimal inhibitory concentration (MIC) and a minimal bactericidal concentration (MBC) of 3.91 mg/mL. Tea leaf extract and the extracts of A. marmelos and T. catappa were also able to inhibit urease enzyme production and the adhesion of all tested H. pylori on epithelial cells. Therefore, tea leaf extracts and plant extracts of A. marmelos, and T. catappa could be considered as antioxidants and potential agents for the treatment of H. pylori infection.