[Isolation of an antibacterial active tropolone from a Pseudomonas cepacia strain]. / Isolierung eines antibiotisch wirkenden Tropolons aus einem Stamm von Pseudomonas cepacia.

In the strain ATCC 17759 of Pseudomonas cepacia a highly antibacterial active substance was found, which could be identified as the tropolone bis-(3-hydroxy-2-oxocyclo-heptatrien-(3,5,7)-yl)-sulfide. This data confirm that tropolones are not only found in plants like western red cedars, but are also occurring as metabolites in bacteria. At least in Pseudomonas cepacia there seems to be an interesting reciprocal correlation between the production of tropolones and of phenacines. The purified tropolone showed a broad antibacterial activity spectrum against gram-positive and gram-negative microorganisms. The MIC-values were situated between 12.5 and greater than 100,0 microgram/ml.

The metabolism of benzyl isothiocyanate and its cysteine conjugate.

1. The corresponding cysteine conjugate was formed when the GSH (reduced glutathione) or cysteinylglycine conjugates of benzyl isothiocyanate were incubated with rat liver or kidney homogenates. When the cysteine conjugate of benzyl isothiocyanate was similarly incubated in the presence of acetyl-CoA, the corresponding N-acetylcysteine conjugate (mercapturic acid) was formed. 2. The non-enzymic reaction of GSH with benzyl isothiocyanate was rapid and was catalysed by rat liver cytosol. 3. The mercapturic acid was excreted in the urine of rats dosed with benzyl isothiocyanate or its GSH, cysteinyl-glycine or cysteine conjugate, and was isolated as the dicyclohexylamine salt. 4. An oral dose of the cysteine conjugate of [14C]benzyl isothiocyanate was rapidly absorbed and excreted by rats and dogs. After 3 days, rats had excreted a mean of 92.4 and 5.6% of the dose in the urine and faeces respectively, and dogs had excreted a mean of 86.3 and 13.2% respectively. 5. After an oral dose of the cystein conjugate of [C]benzyl isothiocyanate, the major 14C-labelled metabolite in rat urine was the corresponding mercapturic acid (62% of the dose), whereas in dog urine it was hippuric acid (40% of the dose). 5. Mercapturic acid biosynthesis may be an important route of metabolism of certain isothiocyanates in some mammalian species.