Abstract
New bis-type quaternary ammonium compounds (QACs), 1, 1'-(decanedioyl) bis (4-methy1-4-alkylpiperazinium iodide) s (DMAP-n, n: carbon number in the N-alkyl chains, n = 6, 8, 10, 12, 14, 16), which have a gemini structure containing two piperazinium rings connected with the spacer of the decanedioyl group, were developed. Their antimicrobial characteristics were investigated against 16 strains of bacteria and 9 strains of fungi and compared with those of 1, 4-dimethyl-1, 4-dialkylpiperazinium diiodides (DMPA-n), 1-methyl-1-alkylpiperazinium iodides (MPA-n), benzyldimethyldodecylammonium chloride (BAC) or 2-(4-thiazolyl)-benzimidazole (TBZ). DMAP-10 and DMAP-12 had the highest antimicrobial activity in the DMAP-n series against Escherichia coil K12 W3110 and Staphylococcus aureus IFO 12732. DMAP-12 also exhibited a wide-ranging antimicrobial spectrum, and showed more effective antimicrobial activity against bacteria than DMPA-12 and BAC, and more effective activity against fungi than DMPA-12 and TBZ. The activity of DMAP-12 was not influenced by pH and temperature like other bis-type QACs. It was found in the DMAP-n, DMPA-n and MPA-n series that the antimicrobial activity and hemolytic activity against human erythrocytes showed some correlation with their molecular hydrophobicity.
