Occurrence of S-methyl thioesters in urines of humans after they have eaten asparagus.

Gas chromatography-mass spectrometry was used to determine the odor-causing agent (or agents) present in the urines of humans after they have eaten asparagus. S-Methyl thioacrylate and S-methyl 3-(methylthio)thiopropionate were identified from methylene chloride extracts of such urines and appear to be the odor-causing compounds. Methanethiol, the previously reported odor-causing agent, was not detected in these methylene chloride extracts.