4-Hydroxy-2-alkylquinoline

4-Hydroxy-2-alkylquinolines (HAQs) are a class of intracellular signaling molecules associated with iron chelation. HAQs are produced by various types of bacteria, such as Pseudomonas aeruginosa,^[1] and are involved in quorum sensing.

Chemical structure of 4-hydroxy-2-heptylquinoline, a common form of HAQ

The overproduction of these molecules, with their pro-oxidative effects, leads to antibiotic properties.