5-Alkyloxytryptamines are membrane-targeting, broad-spectrum antibiotics

Area of Science:

• Microbiology
• Medicinal Chemistry

Background:

• Antibiotic adjuvant therapy offers a strategy to enhance existing antibiotics by using co-administered small molecules.
• Adjuvants can lower antibiotic doses, broaden antimicrobial spectrum, and combat emerging drug resistance.

Purpose of the Study:

• To explore 5-alkyloxytryptamines as a novel class of broad-spectrum antibacterial adjuvants.
• To determine the structural requirements for antibacterial activity and membrane permeability.

Main Methods:

• Synthesis of 5-alkyloxytryptamine analogs with varying alkyl chain lengths and functional groups.
• Evaluation of antibacterial activity and membrane permeability in Gram-positive and Gram-negative bacteria.
• Assessment of adjuvant activity with clinical antibiotics against resistant bacterial strains.

Main Results:

• Optimal antibacterial activity requires an alkyl chain length of 6-12 carbons and a primary ammonium group.
• Alkyl chains of 6-10 carbons enhance membrane permeability in both Gram-positive and Gram-negative bacteria.
• 5-alkyloxytryptamines significantly reduced minimum inhibitory concentrations (MICs) for antibiotics like chloramphenicol and ciprofloxacin against Salmonella typhimurium, Acinetobacter baumannii, and Staphylococcus aureus.

Conclusions:

• 5-alkyloxytryptamines represent a new class of effective broad-spectrum antibiotic adjuvants.
• These compounds show potential for use in combination therapies to combat antibiotic-resistant infections with reduced mammalian cell toxicity.