Quaternary ammonium salts substituted by 5-phenyl-1,3,4-oxadiazole-2-thiol as novel antibacterial agents with low cytotoxicity

Abstract

Twenty-one novel 5-phenyl-1,3,4-oxadiazole-2-thiol (POT) substituted N-hydroxyethyl quaternary ammonium salts (6a-g, 7a-g, 8a-g) were prepared and characterized by FTIR, NMR and elemental analysis. Compounds 6a, 6c and 8a were confirmed by X-ray single-crystal diffraction. They display the unsurpassed antibacterial activity against S. aureus, α-H-tococcus, E. coli, P. aeruginosa, Proteus vulgaris, Canidia Albicans, especially 6g, 7g, 8g with dodecyl group. Compounds 8a-d with N,N-dihydroxyethyl and POT groups display unsurpassed antibacterial activity and nontoxicity. The structure-activity relationships indicate that POT and flexible dihydroxyethyl group in QAS are necessary for antibacterial activity and cytotoxicity. SEM and TEM images of E. coli morphologies of 8d show the antibacterial agents can adhere to membrane surfaces to inhibit bacterial growth by disrupting peptidoglycan formation and releasing bacterial cytoplasm from cell membranes.

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Twenty-one novel 5-phenyl-1,3,4-oxadiazole-2-thiol (POT) substituted QAS were prepared with the unsurpassed antibacterial abilities. POT and flexible dihydroxyethyl group in QAS are necessary for activity. SEM and TEM images of E. coli morphologies of 8d show it can adhere to membrane surfaces to inhibit bacterial growth by disrupting peptidoglycan formation and releasing bacterial cytoplasm.

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