Paper
The influence of chemical constitution on antibacterial activity. V. The antibacterial action of 8-hydroxyquinoline (oxine).
Published Jun 1, 1950 · S. Rubbo, A. Albert, M. Gibson
British journal of experimental pathology
33
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0
Influential Citations
Abstract
IN Part III of this series (Albert, Rubbo, Goldacre and Balfour, 1947) 8-hydroxyquinoline and its isomerides were examined for antibacterial activity. Of the seven isomeric mono-hydroxyquinolines, only oxine (8-hydroxyquinoline) was active, and only oxine was found to be capable of forming non-ionized complexes with divalent metallic ions, a process known as chelation (Albert and Gledhill, 1947). On the evidence then available it was thought that this undoubted connection between chelation and antibacterial activity might be due to the masking (or removal) by oxine of a metallic ion forming an essential part of a metabolic process. The present study is an extension of Part III, in which a closer analysis of the mode of action of oxine has been made using a greater variety of test organisms. As a result of further work it has become possible to confirm our original conception that oxine acts by chelating with the ions of certain heavy nmetals. The mechanism by which this chelation injures the cell is found, in the case of Gram-positive organisms at least, to be more complex than had been suggested. Sufficient data have now been accumulated fo show that the mode of action of oxine is distinct from that established for other antibacterial agents. The observations recorded here show that oxine is active against staphylococci and other Gram-positive types only when iron or cupric ions are present in the medium. Oxine is devoid of all antibacterial activity in media where the concentration of these ions falls below a necessary, though truly minute, value. These observations are open to two interpretations. The first is that oxine reacts with the iron or cupric ion to form a toxic metal-oxine complex which exerts a direct lethal action. The second is that oxine removes a metallic component from a vitaJ cellular enzyme-system, thus exposing an oxidizable group (normally protected by the metal) to destruction by an ironor copper-catalysed oxidation. It will be evident from this paper that any complete explanation of the mode of action of oxine must account for a number of apparently unrelated phenomena.
Oxine, the only active 8-hydroxyquinoline, acts against bacteria by chelating with heavy metal ions, with a complex mechanism of cell injury in Gram-positive organisms.
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