Conversion of indole to oxindole under methanogenic conditions

When indole was incubated under methanogenic conditions with an inoculum of sewage sludge, the chemical was metabolized with 10 days and temporary formation of an intermediate was observed. The metabolite was isolated by thin-layer chromatography and determined to be 1,3-dihydro-2H-indol-2one (oxindole) by UV spectroscopy (lambdaMAX, 247 nm) and mass spectrometry (m/z, 133). The methane produced (net amount) indicated nearly complete mineralization of indole.