1999 Research paper on hydrogen sulfide and methanethiol in the cecal mucosa

1999 Paper

Detoxification of hydrogen sulfide and methanethiol in the cecal mucosa.

Levitt MD, Furne J, Springfield J, Suarez F, DeMaster E
Minneapolis Veterans Affairs Medical Center, Minneapolis, Minnesota 55417, USA

The acute toxicity of H2S and CH3SH appears to result, like that of cyanide, from the inhibition of cytochrome oxidase. In vitro measurements have shown that H2S actually is a slightly more potent inhibitor of cytochrome oxidase than is cyanide
Note: This introduction is the opinion of the author, and may not be wholly accurate

This group of researchers in Minneapolis seem to have done a lot of work regarding sulfides in the gut and their absorption. At the moment it is unknown as to if or how dysbiosis may relate to metabolic body odor, especially fecal body odor, but it would seem that chemicals produced in the gut will be responsible for many of the smells of fecal body odor, including sulfides.

Whilst the liver plays the main role in detoxifying circulating toxins, it also makes evolutionary sense for these type of detoxifying enzymes to be available where sensibly needed, such as the gut. These will often once again be of the xenobiotic-metabolizing enzyme variety, in what is known as part of the the 'first pass metabolism'. That means any absorbable toxins in the gut could be detoxified on-site, but if absorbed they then have to get past the liver, before getting into the systemic circulation. It's known that the P450 enzyme, 3A4 is present in the small intestine, for instance.

All the papers to do with the gut and metabolism by the above researchers are interesting. In this case, they look to see how hydrogen sulfide and methanethiol are metabolized in a rats cecum. These two compounds are likely present in the human gut, probably generated from sulfate reducing bacteria (?) feeding off sulfur in the colon. Perhaps some with fecal body odor have found they can smell of rotten egg when their recent diet has included poorly absorbed sulfurs. We can't be sure why this would be, but this could be one theory.

They expected the route of detoxification of the compounds on-site in the colon (by the colon lining cells, presumably) to be:

H2S methylated to methanethiol which would be altered to dimethylsulfide.
Instead they found methanethiol was demthylated into H2S which was then oxidised to thiosulfate

Their interest was because it has been proposed that these compounds may be implicated in ulcerative colitis. They will be unaware of fecal body odor.

Of note is that the researchers find that both compounds have an inhibiting effect on the cytochromeP450 first pass metabolism enzymes, apparently stronger than cyanide does.

Pubmed abstract

Full paper