Discovery raw data files were converted to .cdf format using the file converter tool in Xcalibur version 2.2 (Thermo Scientific). Peak detection, integration and alignment were performed with the open-source software XCMS version 1.30.3 (Smith et al. 2006). The following XCMS settings were used: For peak detection and integration with the centWave algorithm, ppm = 10, snthr = 5, peakwidth = c(5.15), mzdiff = −0.01, prefilter = c(6,100), fitgauss = TRUE; for alignment with Obiwarp, distFunc = “cor”, profStep = 1, grouping parameters bw = 1, mzwid = 0.005, minfrac = 0.5. Isotopes and adducts were not removed.