In the left panel: comparison of the extracted ion chromatograms of m/z 197.1185 (mass tolerance < 5 ppm) in full-scan MS of: (a) normal urine sample; (b) glucuronidase treated urine sample; (c) seaweed extract; (d) loliolid commercial standard (in the front) and synthesized loliolid glucuronide from the loliolid commercial standard (in the back). The chromatographic peaks of M2 and M3, namely loliolid glucuronide and isololiolide glucuronide, are at RT 5.31 and 5.37, respectively. The chromatographic peaks of the deconjugated (glucuronidase treated) M2 and M3, namely loliolid and isololiolide, are at RT 5.61 and 5.78, respectively. In the right panel: comparison of the MS/MS spectra of the m/z 197.1185 shown in the relative extracted ion chromatograms, in particular: in (a1) and (a2) MS/MS of the peak at RT 5.31 and 5.37, respectively; in (b1) and (b2) MS/MS of the peak at RT 5.62 and 5.77, respectively; in (c1) and (c2) MS/MS of the peak at RT 5.61 and 5.78, respectively; in (d1) MS/MS of the peak at RT 5.77. The collision energy used for all MS/MS was 14 eV.