TABLE 1.

UV absorption spectra and ESI mass spectral properties of metabolites formed from the degradation of caffeine, theophylline, and 3-methylxanthine by P. putida CBB5

Growth substrateMetaboliteUV λmax (nm)m/z value of protonated molecular ionaIdentity of metabolite
Caffeine (UV λmax, 273 nm; m/z 195)I271NDb Paraxanthine
II271181Theobromine
III2691677-Methylxanthine
IV196, 267153Xanthine
V240, 284169Uric acid
Theophylline (UV λmax, 271 nm; m/z 181)VI231, 2871971,3-Dimethyluric acid
VII231, 2841831-Methyluric acid
VIII234, 2871833-Methyluric acid
IX198, 2671671-Methylxanthine
X198, 2711673-Methylxanthine
IV196, 267153Xanthine
V240, 284169Uric acid
3-Methylxanthine (UV λmax, 198 and 271 nm;VIII234, 2871833-Methyluric acid
    m/z 167)IV196, 267153Xanthine
V240, 284169Uric acid
  • a m /z values were determined by ESI mass spectrometry operating in the positive-ion mode.

  • b ND, not detected. No ESI mass spectrum was detected for paraxanthine, possibly because of the low concentration of this metabolite in spent media. Metabolite I was determined to be paraxanthine by comparing its HPLC Rt and UV spectrum with those of an authentic standard.