ANTIBACTERIAL EFFECT OF -DIMETHYL-5-ISOXAZOLYL)-1,4-NAPHTHOQUINONE-4-IMINE ON STAPHYLOCOCCUS-AUREUS

The mechanism by which a new naphthoquinone derivative, the -dimethyl- 5-isoxazolyl)-1,4-naphthoquinone-4-imine (INQI-E) has antibacterial ef fect against Staphylococcus aureus was studied. The interaction of INQ I-E with the bacteria was followed by absorption spectroscopy at 323 a nd 490 nm. The absorption band of INQI-E at 490 nm undergoes a hypochr omic shift with a decrease of intensity. This effect was found to be r eversible by oxygenation during the first hours of incubation. The par ticipation of an oxidation-reduction process related to the respirator y chain was demonstrated by oxygen consumption. An increase in O-2 upt ake and inhibition of S. aureus growth was observed. Experiments with three inhibitors of the respiratory chain demonstrated that the pathwa y induced by INQI-E was antimycin-resistant and KCN- and salicylhydrox amic acid (SHAM)-sensitive, which suggests that INQI-E is capable of d iverting the normal electron flow to an alternate superoxide-producing route. On the other hand, experiments with Tiron, a specific scavenge r of superoxide, hindered the effect of INQI-E against S. aureus, indi cating that the inhibitory growth effect of this quinone-imine is main ly due to the production of the cytotoxic superoxide radical.