| |||
| Names | |||
|---|---|---|---|
| Preferred IUPAC name 1,2-Dithiolane-4-carboxylic acid | |||
| Other names 1,2-Dithiacyclopentane-4-carboxylic acid | |||
| Identifiers | |||
3D model (JSmol) | |||
| ChEBI | |||
| ChemSpider |
| ||
| KEGG |
| ||
| UNII | |||
| |||
| |||
| Properties | |||
| C4H6O2S2 | |||
| Molar mass | 150.21 g·mol−1 | ||
| Appearance | Colorless solid | ||
| Density | 1.50 g cm−3 | ||
| Melting point | 75.7 to 76.5 °C (168.3 to 169.7 °F; 348.8 to 349.6 K)[2] | ||
| Boiling point | 323.9 °C (615.0 °F; 597.0 K) at 760mmHg | ||
| Hazards | |||
| Flash point | 149.7 °C (301.5 °F; 422.8 K) | ||
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
Asparagusic acid is anorganosulfur compound with themolecular formula C4H6O2S2 andsystematically named 1,2-dithiolane-4-carboxylic acid. The molecule consists of aheterocyclicdisulfidefunctional group (a 1,2-dithiolane) with acarboxylic acid side chain. It is found inasparagus and is believed to be the metabolic precursor to odorous sulfur compounds responsible for the distinctive smell ofurine which has long been associated with eating asparagus.[3][4]
The material was originally isolated from an aqueous extract ofAsparagus officinalis, a springvegetable.[5] It is aderivative of the cyclicdisulfideorganic compound1,2-dithiolane with acarboxylic acidfunctional group bound to carbon-4 of theheterocycle.Biosynthetic studies revealed that asparagusic acid is derived fromisobutyric acid.[6] Asparagusic acid is a colorless solid with amelting point of 75.7–76.5 °C,[2] higher than that of the corresponding dithiol: dihydroasparagusic acid (or γ,γ-dimercaptoisobutyric acid), at 59.5–60.5 °C.[7]
A convenient synthesis of asparagusic acid has been developed from a commercially availablediethyl malonate derivative starting material, improving on the prior method of Jansen.[5] Diethyl bis(hydroxymethyl)malonate is treated withhydroiodic acid to yield β,β'-diiodoisobutyric acid after decarboxylation and ester hydrolysis (with removal of volatileethanol andcarbon dioxide). Dihydroasparagusic acid, the reduced (dithiol) form of asparagusic acid, is produced by sequential reaction with sodiumtrithiocarbonate (Na2CS3) andsulfuric acid; subsequent oxidation with hotdimethyl sulfoxide yields asparagusic acid.[1]
Observations that eating asparagus results in a detectable change in the odour ofurine have been recorded over time. In 1702,Louis Lémery noted "a powerful and disagreeable smell in the urine",[8] whilstJohn Arbuthnot noted that "asparagus ... affects the urine with afoetid smell."[9][10]Benjamin Franklin described the odour as "disagreable",[11] whilstMarcel Proust claimed that asparagus "transforms my chamber-pot into a flask of perfume."[10][12] As early as 1891,Marceli Nencki had attributed the smell tomethanethiol.[13][14] The odour is attributed to a mixture of sulfur-containingmetabolites of asparagusic acid.[3][4][15][16]
The origin of asparagus urine is asparagusic acid, a substance unique to this vegetable.[17][18] Most studies of the compounds responsible for the odour of asparagus urine have correlated the appearance of the compounds above with asparagus consumption; they appear as little as 15 minutes after consumption.[10] However, this does not provide information on thebiochemical processes that lead to their formation.
Asparagusic acid andlipoic acid are similar in that both possess a 1,2-dithiolane ring with a carboxylic acid tethered to it; indeed, it has been reported that asparagusic acid can substitute for lipoic acid in α-keto-acid oxidation systems such as thecitric acid cycle.[18] The (R)-(+)-enantiomer of α-lipoic acid is acofactor in thepyruvate dehydrogenase complex and is essential foraerobic metabolism. The degradation pathway of lipoic acid has been well studied and includes evidence of reduction of the disulfide bridge,S-methylation, and oxidation to produce sulfoxides.[19] Similar transformations of asparagusic acid would lead to metabolites like this detected in asparagus urine. Synthetic work has confirmed the relative ease of oxidation of asparagusic acid to yieldS-oxides of the dithiolane ring.[1] The rate of degradation appears highly variably between subjects; the typicalhalf-life for odour disappearance is around 4 h with abetween subject variability of 43.4%.[20]
In the small minority of people who do not produce these metabolites after consuming asparagus, the reason may be as simple as asparagusic acid not being taken into the body from the digestive tract[3] or that these individuals metabolise it in such a way as to minimise the release of volatile sulfur-containing products.[10]
An Essay Concerning the Nature of Ailments.
{{cite book}}:ISBN / Date incompatibility (help)changer mon pot de chambre en un vase de parfum
Media related toAsparagusic acid at Wikimedia Commons