2-Hydroxymethyl-3-methylquinoxaline 1:4-dioxide: a metabolite of 2:3-dimethylquinoxaline 1:4-dioxide active against gram-negative bacteria.

The antibacterial activity of certain quinoxaline 1:4-dioxides has been described by McIlwain (1943), Wiedling (1945), Frisk (1946), and Iland (1948), and previous papers from this Laboratory described their action on Entamoeba hi8tolytica (Jones, Landquist & Stewart, 1953), and on viruses of the lymphogranuloma-psittacosis group (Hurst et al. 1953). We have found that quinoxaline 1:4dioxides show activity against Gram-negative bacteria, including Salmonella dublin and Salin. typhi, either in vitro or in infections in mice (Table 1). Similar observations have recently been published by Coulthard & Hale (1955). 2: 3 -Dimethylquinoxaline 1: 4 dioxide (7218) proved to be one ofthe most effective agents against Salm. dublin infections in mice, being more active than aureomycin, but it had little activity in vitro. Similar results were obtained with E8cherichia coli and with Clo8tridium welchii, which was the most sensitive. It appeared, therefore, that an active metabolite was formed in vivo, and it was found that the blood and urine of sheep dosed with 7218 became active against Salm. dublin and Cl. welchii within an hour of dosing. Isolation of the metabolite from sheep's urine was attempted, the urine being treated with lead acetate until no further precipitation of lead salts occurred, then concentrated, and subjected to various extraction procedures. The concentration ofthe biologically active fraction was followed at first by assays against Cl. welchii and later by examination of the ultraviolet absorption spectra for bands characteristic of quinoxaline di-N-oxides (Fig. 1). Undue exposure of the solutions to light was avoided. The active metabolite was finally separated from unchanged 7218 by partition chromatography and was obtained as crystalline solid with an elementary composition corresponding to C0IHIL003N2 On the basis of the absence of obvious phenoic characteristics, a comparison of its absorption spectrum with those of numerous quinoxaline derivatives, and its non-identity with the di-N-oxide of 5or 6-hydroxy2:3-dimethylquinoxaline, it was concluded that the metaboite is 2-hydroxynethyl-3-methylquinoxaline 1:4-dioxide, and this was confirmed by synthesis of this compound (12811).