Structural and biological characterization of one antibacterial acylpolyamine isolated from the hemocytes of the spider Acanthocurria gomesiana

We have isolated a 417 Da antibacterial molecule, named mygalin, from the hemocytes of the spider Acanthoscurria gomesiana. The structure of mygalin was elucidated by tandem mass spectrometry (MS/MS) and by two spectroscopic techniques, nuclear magnetic resonance (NMR) and ultraviolet (UV) spectroscopy. Mygalin was identified as bis-acylpolyamine N1,N8-bis(2,5-dihydroxybenzoyl)spermidine, in which the primary amino groups of the spermidine are acylated with the carboxyl group of the 2,5-dihydroxybenzoic acid. Mygalin was active against Escherichia coli at 85 μM, being this activity inhibited completely by catalase. Therefore, the antibacterial activity of mygalin was attributed to its production of hydrogen peroxide (H2O2). The putative mechanisms of formation of H2O2 from mygalin are discussed. To our knowledge this is the first report of one bis-acylpolyamine with antibacterial activity purified from animal source.