page_title: Asparagus
section_title: Chemistry
hierarchical_section_title: Asparagus / Effects on urine / Chemistry
caption_attribution_description: Asparagus in Autumn foliage
context_page_description: Asparagus, or garden asparagus, folk name sparrow grass, scientific name Asparagus officinalis, is a perennial flowering plant species in the genus Asparagus. Its young shoots are used as a spring vegetable.
  It was once classified in the lily family, like the related Allium species, onions and garlic. However, genetic research places lilies, Allium, and asparagus in three separate families—the Liliaceae, Amaryllidaceae, and Asparagaceae, respectively—with the Amaryllidaceae and Asparagaceae being grouped together in the order Asparagales. Sources differ as to the native range of Asparagus officinalis, but generally include most of Europe and western temperate Asia. It is widely cultivated as a vegetable crop.
context_section_description: Certain compounds in asparagus are metabolized to yield ammonia and various sulfur-containing degradation products, including various thiols and thioesters, which give urine a characteristic smell.
  Some of the volatile organic compounds responsible for the smell are:
  methanethiol
  dimethyl sulfide
  dimethyl disulfide
  bis(methylthio)methane
  dimethyl sulfoxide
  dimethyl sulfone
  Subjectively, the first two are the most pungent, while the last two (sulfur-oxidized) give a sweet aroma. A mixture of these compounds form a "reconstituted asparagus urine" odor.  This was first investigated in 1891 by Marceli Nencki, who attributed the smell to methanethiol. These compounds originate in the asparagus as asparagusic acid and its derivatives, as these are the only sulfur-containing compounds unique to asparagus. As these are more present in young asparagus, this accords with the observation that the smell is more pronounced after eating young asparagus. The biological mechanism for the production of these compounds is less clear.
  The onset of the asparagus urine smell is remarkably rapid while the decline is slower. The smell has been reported to be detectable 15 to 30 minutes after ingestion and subsides with a half-life of approximately 4 hours.
caption: Asparagus foliage turns bright yellow in autumn
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