Biotransformation of aesculin by human gut bacteria and identification of its metabolites in rat urine

Figure 1 Biotransformation of aseculin by anaerobic human gut bacteria. The gut bacteria comprised 20 pooled fecal samples from healthy volunteers. Incubation was performed under anaerobic conditions (80% N2, 10% CO₂, 10% H2) at 37°C for defined time periods. Ten millilitre of samples was collected at 0, 2, 4, 8, 12, 16, 24, 48 and 72 h, respectively post-incubation. Aesculin and metabolites were then extracted with methanol and analyzed by HPLC. The vertical axis shows the relative values for the concentration of aesculin and/or its metabolite. The horizontal axis indicates the HPLC overflow time.

Figure 2 Summary of aesculetin metabolites identified in rat urine. ¹The position(s) of methylation and/or conjugation(s) may be exchangeable on the two phenols.

Figure 3 Proposed characteristic (-) CAD-MS/MS fragmentations for aesculetin metabolites.

Figure 4 HPLC UV-chromatograms of reference standards for aesculetin and aesculin (A), M2 isolated from rat urine (B), and a rat urine sample dosed with aesculetin with assignments of aesculetin urinary metabolites (C).

Figure 5 Aesculetin LC/(+)ESI-MS and MS/MS spectral data.