Sarcotoxin Pd, a new antimicrobial and spermicidal peptide from the insect paederus dermatitis.

Introduction: Sexually transmitted infections and unplanned pregnancies are two great concerns in the reproductive health. Different agents are used for male contraception but it is necessary to introduce other compounds that have antimicrobial properties in order to reduction of sexually transmitted diseases as well as male contraception. The aim of this study was to purify new spermicidal peptides with antimicrobial properties from Paederus dermatitis (Pd). Materials and Methods: The peptide purification was done with gel filtration and Reverse-Phase High Performance Liquid Chromatography (HPLC). The sequencing was carried out by Mass/Mass. The antimicrobial activity was tested by Radial Diffusion Assay (RDA) and Minimal Inhibitory Concentration (MIC) methods. After preparation of normozoospermic specimens, different doses of 3, 7.5, 15, 30 and 125 μg/ml were tested at different time intervals (0.3, 5, 10, 15 min). Eosin staining method was applied for sperm viability detection. Results: The results showed that the sarcotoxin Pd showed considerable antimicrobial activity against Gram positive and Gram negative bacteria [minimum inhibitory concentrations (MIC), 6.12-19.24 μg/ml] as well as fungi (MIC, 18.62 to 25.26 μg/ml). In addition, this new peptide showed no hemolytic activity against human red blood cell. This peptide is composed of 34 amino acids and its sequence is: GWLKKIGKKIE RVGQHTRGLGIAQIAANVAATA. Total spermicidal activity was shown after addition of 125 μg/ml for 0.3 min. Conclusion: Preliminary results showed potential spermicidal as well as antimicrobial activities of sarcotoxin Pd. It seems this peptide is potential candidate in order to use in male contraception which can be used as a spermicidal agent in male condoms. [ABSTRACT FROM AUTHOR]