The UV and MRM chromatograms of one rat perfusion samples collected at 150 min after the start of 10 μM naringenin intestinal perfusion. A: UPLC chromatogram; B, C, and D: MRM chromatograms of M1 and M2, internal standard (IS, daidzein) and naringenin in duodenum perfusate; E, F, and G: MRM chromatograms of M1 and M2 in jejunum, ileum, and colon perfusate; H: MRM chromatograms of M2 in bile sample which was diluted 10 times with acetonitrile before analysis. M1 peak in panels B, E and F is signified by the (very) small valley following the initial rise (see arrow), whereas those in panels A and G were clearer. No M1 was detected in H.