RESUMEN
Infection with Helicobacter pylori is the most common cause of stomach and duodenal ulcers. About more than 80% of people are infected with H. pylori in developing countries. H. pylori uses urease enzyme product "ammonia" in order to neutralize and protect itself from the stomach acidic condition and urease enzyme activity has been shown to be essential to the colonization of H. pylori. Inhibitory activity of 20 traditional medicinal plants were examined and evaluated against Jack bean urease activity by Berthelot reaction to obtains natural sources of urease inhibitors. Each herb was extracted using 80% aqueous methanol, then tested its IC[50] value was determined. Eight of the whole 20 studied plants crude extracts were found the most effective with IC[50] values of less than 100 micro g/mL including Laurus nobilis, Zingiber officinale, Nigella sativa, Angelica archangelica, Acorus calamus, Allium sativum,Curcuma longa, and Citrus aurantium extracts, from which most potent urease inhibitory was observed for Zingiber officinale, Laurus nobilis, and Nigella sativa with IC[50] values of 48.54, 48.69 and 59.10 micro g/mL, respectively