Large scale screening of commonly used Iranian traditional medicinal plants against urease activity

137 Iranian traditional medicinal plants were examined against Jack bean urease activity by Berthelot reaction. Each herb was extracted using 50% aqueous methanol. The more effective extracts were further tested and their IC50 values were determined.37 plants out of the 137 crude extracts revealed strong urease inhibitory activity (more than 70% inhibition against urease activity at 10 mg/ml concentration). Nine of the whole studied plants crude extracts were found as the most effective with IC50 values less than 500 μg/ml including; Rheum ribes, Sambucus ebulus, Pistachia lentiscus, Myrtus communis, Areca catechu, Citrus aurantifolia, Myristica fragrans, Cinnamomum zeylanicum and Nicotiana tabacum.The most potent urease inhibitory was observed for Sambucus ebulus and Rheum ribes extracts with IC50 values of 57 and 92 μg/ml, respectively.Ureases (urea amidohydrolases, EC (3.5.1.5) are a group of widespread enzymes in nature, classified as the most proficient enzymes (with proficiency more than 1014), stand as protagonist in biochemistry for several reasons. Urease was the first ureolytic enzyme obtained and named in the late nineteenth century, with landmark significance in enzymology as the first enzyme crystallized (in 1926 by Sumner) to approve the proteinous nature of the enzymes [1]. Also, as ascertained by Dixon et al. in 1975, urease was the first enzyme shown to possess nickel ions in its active site, essential for activity [2]. Since its substrate; urea is pervasively available in nature, urease was important to provide organisms with nitrogen in the form of ammonia for growth [3]. Despite the diversity in the molecular structures of urease, the amino acid sequences of the active sites are principally similar in all of the known them and consequence of this fact is the same catalytic mechanism. The active sites are always located in α subunits and contain the binuclear nickel centre, in which the Ni–Ni distances range from 3.5 to 3.7 Angstrom [4].Urease as