Biological activities of 1,1,6-trisubstituted indanes: Beyond magainin 2

MSI-78 is a peptide analog of naturally occurring magainin 2 isolated from the skin of Xenopus laevis. The peptide is known to have one of the stronge st antibacterial activities in magainin 2 analogs against methicillin-resis tant Staphylococcus aureus (MRSA). To find novel compounds superior to MSI- 78, we have further designed, synthesizing 1,1-di(4-aminobutyl)-6-benzylind ane (PM4) and 1,1-dibenzyl-6-(4-aminobutyl) indane (PM5), and tested their inhibitory ability of the growth of S. aureus. In an in vitro assay, PM4 sh owed the same antibacterial activity against the bacterium as MSI-78, and n on-hemolytic activity against human red blood cells (RBCs) at the MIC (mini mum inhibitory concentration) value, in contrast to the latter. On the othe r hand, PM5 showed stronger antibacterial activity than MSI-78, but being s till accompanied with hemolysis at the MIC value. Otherwise, stronger decar boxylase activity for oxaloacetate was observed in PM5, rather than magaini n 2 analogs or Oxaldie 1 as a control peptide, but not in PM4.