All animals have developed antimicrobial peptides which are distributed in almost all part of their bodies. These components are basic constituents of immune system which are secreted in response to microbial infections and environmental stress to have a homeostasis. All animals especially amphibians, have variety of these peptides and most part of their bodies could secrete such peptides as their immune system, in response to externs. This study is performed aiming introduce new antimicrobial peptides from skin secretion of R. ridibunda. First the samples were collected from different regions of Khorasan province and kept in a standard condition. Crud samples, was collected from skin secretion of R. ridibunda by applying 4-6 volt electricity and washing by 10mM (pH=4.7) buffer phosphate. Then samples which had molecular mass between 1-10kD were condensed and purified using ultra-filtration and RP-HPLC respectively. Finally microbial test was done which elucidated their antimicrobial activity against a large of microbes. Other works on these peptides to determine MIC and other properties is being done.

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