FIG 5.

Presence of DHMA in fecal samples. Metabolites were extracted from fecal samples of SPF (n = 9; 4 to 12 weeks old) and GF (n = 6; 3 to 8 weeks old) mice. DHMA was detected by LC-MS and quantified using a standard curve. DHMA (exact mass, 184.037) was detected in the negative-ion mode as an ion of m/z 183.032 with a confirmatory fragment ion of m/z 137.025. (Top) Extracted ion current (XIC) chromatogram indicating the elution of pure DHMA using a Chromolith RP-18 column. (Inset) Standard curve of DHMA determined over a concentration range of 1 nM to 1 × 10³ nM. (Middle) Representative XIC chromatogram showing the elution of DHMA in a fecal extract from an SPF mouse and a GF mouse. The peak area of DHMA in the fecal extract from the SPF mouse corresponds to a DHMA concentration of 1.9 ± 0.3 μM. (Bottom) Quantitation of DHMA in SPF and GF mice. Note that no DHMA was detected in extracts from GF mice.