title: 5-Alkyloxytryptamines are membrane-targeting, broad-spectrum antibiotics.
abstract: Antibiotic adjuvant therapy represents an exciting opportunity to enhance the activity of clinical antibiotics by co-dosing with a secondary small molecule. Successful adjuvants decrease the concentration of antibiotics used to defeat bacteria, increase activity (in some cases introducing activity against organisms that are drug resistant), and reduce the frequency at which drug-resistant bacteria emerge. We report that 5-alkyloxytryptamines are a new class of broad-spectrum antibacterial agents with exciting activity as antibiotic adjuvants. We synthesized 5-alkyloxytryptamine analogs and found that an alkyl chain length of 6-12 carbons and a primary ammonium group are necessary for the antibacterial activity of the compounds, and an alkyl chain length of 6-10 carbons increased the membrane permeability of Gram-positive and Gram-negative bacteria. Although several of the most potent analogs also have activity against the membranes of human embryonic kidney cells, we demonstrate that below the minimum inhibitory concentration (MIC)-where mammalian cell toxicity is low-these compounds may be successfully used as adjuvants for chloramphenicol, tetracycline, ciprofloxacin, and rifampicin against clinical strains of Salmonella typhimurium, Acinetobacter baumannii and Staphylococcus aureus, reducing MIC values by as much as several logs.
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison, 6424A Biochemical Sciences Building, 440 Henry Mall, Madison, WI 53706, USA.
authors.forename: Katherine C
authors.initials: KC
authors.lastname: Faulkner
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison, 6424A Biochemical Sciences Building, 440 Henry Mall, Madison, WI 53706, USA.
authors.forename: Katherine A
authors.initials: KA
authors.lastname: Hurley
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison, 6424A Biochemical Sciences Building, 440 Henry Mall, Madison, WI 53706, USA; Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA; Department of Biomedical Engineering, University of Wisconsin-Madison, 1550 Engineering Drive, Madison, WI 53706, USA. Electronic address: douglas.weibel@wisc.edu.
authors.forename: Douglas B
authors.initials: DB
authors.lastname: Weibel
mesh_terms: D040981:Acinetobacter baumannii / Q000187:drug effects; D000478:Alkylation; D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000494:pharmacology*; D006090:Gram-Negative Bacteria / Q000187:drug effects*; D016905:Gram-Negative Bacterial Infections / Q000188:drug therapy; D006094:Gram-Positive Bacteria / Q000187:drug effects*; D016908:Gram-Positive Bacterial Infections / Q000188:drug therapy; D057809:HEK293 Cells; D006801:Humans; D012486:Salmonella typhimurium / Q000187:drug effects; D013211:Staphylococcus aureus / Q000187:drug effects; D014363:Tryptamines / Q000737:chemistry* / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D014363:Tryptamines
keywords: Antibacterial; Antibiotic; Bacterial membrane; Serotonin; Tryptamine