Some similarities to :
Wild Asparagus (Asparagus prostratus) but that is low and prostrate and is bluish green whereas (Garden) Asparagus is tall, upright and green. Garden Asparagus is much more likely to be found in the wild than is Wild Asparagus, which is rather rare.
Slight resemblance to : Fennel in that the leaves are finely divided, but the flowers are totally different.
Uniquely identifiable characteristics
No relation to : Bath Asparagus (Ornithogalum pyrenaicum) which is also known as Spiked Star-of-Bethlehem whose stems are also edible and eaten like garden asparagus. It is a member of the Lily Family and was once abundant in the city of Bath, England.
Not to be confused with: Sea Arrow-grass nor with Marsh Arrow-grass nor with 'Poor Man's Asparagus' which are different plants altogether.
The leaves of Garden Asparagus can resemble those of Fennel when its flowers are not yet out.
Asparagus, or Garden Asparagus has long been known by what some now regard as a nick-name, but in the past (as long as three Centuries ago or more) was used frequently, that word being 'Sparrowgrass'. When grown as a vegetable it is allowed to grow high with many feathery leaves but in autumn is cut down to a finger-length stub. In the second year the sparrowgrass spears are harvested when they are no higher than 6 inches, cutting them off 2 inches below soil level.
Several of the 300 species of Asparagus are used as house plants, where they may be better known to florists and gardeners as
Asparagus Fern (Asparagus plumosus). Asparagus is dioecious, meaning it has male and female flowers on separate plants.
When eaten, Sparrowgrass makes the urine of people smell within just 20 minutes of consumption, although not everyone can smell it. Sparrowgrass synthesises a sulfurous compound called Asparagusic Acid and its corresponding dithiol, dihydroasparagusic acid, which are both unique to Asparagus. When consumed, an enzyme breaks the compounds down into odorous compounds excreted in the urine. These malodorous compounds all contain sulfur and include
Methyl sulfonyl methane (
Dimethyl Sulfone). The berries are mildly poisonous.
Grows not only in gardens but wild on sea cliffs and on sand dunes and other waste ground.
Asparagusic Acid and the double-thiol derivative Dihydro-Asparagusic Acid (or dimercaptoisobutyric acid) is uniquely present only in Asparagus. It is synthesized within Asparagus from Isobutyric Acid which is present in many plants. But obviously, a source of sulfur is also required, which may come from one of the two sulfur-containing amino acids, Cysteine or Methionine.
CHEMICALS INVOLVED in the SMELL OF URINE
(after consumption of Asparagus)
The above two compounds are the main malodorous factors of urine after ingestion of asparagus. Methanethiol, a gas better known as methyl mercaptan CH3SH, has the malodorous smell of rotting cabbage which is also present in bad breath, some cheeses and, marsh gas and natural gas. It is created in the decay of organic matter. Bacteria can convert methanethiol into dimethyl sulfide. Methanethiol is a weak acid, and in the marine environment may be responsible for the dissolution of some metals, mercury being an obvious candidate. At high concentrations it is neurotoxic, concentration should be kept below 10ppm. The odour threshold is 0.002ppm which provides adequate warning.
Dimethyl sulfide (DMS) (CH3)2S, as well as dimethyl sulfoxide (DMSO (CH3)2S:O, depicted below) are emitted into the atmosphere by phytoplankton in the oceans. DMS also smells of rotting cabbage, but has a higher odour threshold of about 0.05ppm. DMS contributes to the flavour of cabbage, asparagus and seafoods when cooked, and is added as a flavouring to food. DMS is the most abundant biological sulfur containing compound in the atmosphere where it oxidizes into DMSO, sulfur dioxide and eventually into sulfuric acid. High in the atmosphere these sulfates act as condensation nuclei for cloud formation. Thereafter, when it falls to Earth it is responsible for acid rain. Burning sulfur containing substances like coal contributes more acid rain. DMS is present in most wines (as a desirably characteristic if below a certain concentration and as an off-flavour if high) and it also emanates from cooked cabbage, asparagus and truffles.
The following six compounds contribute less to the smell
Dimethyl disulfide (DMDS) is found in plants belonging to the Cabbage Family and in crude oil. It is one of 36 identified compounds in the malodorous smell emitted from sewage works.
Bis(methylthio)methane (aka bis(methylmercapto)methane, 2,4-dithiapentane, and truffle sulfide) is an important contributor to the flavour of truffles, and is added as the primary ingredient (besides olive oil) to synthetically produced and so called 'truffle oil'. However, the taste of truffles is multi-dimensional and caused by several chemicals not present in the cheap synthetic 'truffle oils'.
These last two do not smell, but are non-the-less identified compounds in the urine of people who have consumed asparagus in the last 20 minutes.
Dimethyl sulfoxide (DMSO) was recently made famous by Sir James Lovelock with his Gaia hypothesis where it was discovered that it is being produced and released into the atmosphere (detailed above) as a result of the action of trillions of minute marine organisms. Before that it was once hailed as a wonder super-drug in the 1970's until it fell into disrepute shortly afterwards. It is still used medicinally, applied externally as an analgesic, It is an excellent solvent for many kinds of chemicals, and is used as a paint-stripper. It is readily absorbed through the skin, and thus one medical use is to take other drugs into the body when applied topically, but it can also transport other unwanted deadly poisonous solutes into the body by this mechanism; extreme care needs to be taken in the laboratory. Absorbed through the skin or taken internally it causes a taste sensation in the mouth like those of fish, onion, garlic or oyster, possibly shortly afterwards accompanied by visual disturbances, sensitivity to light, headache and skin irritation. It is probably neurotoxic to the young developing brain at doses as low as 0.3ml/kg body weight, so special caution should be exercised!
MSM, or Methylsulfonyl methane (aka methyl sulfone and dimethyl sulfone) occurs naturally in many primitive plants and is present in smaller amounts in food. It is marketed in health shops as a drug to reduce the effects of arthritis in the knee, although efficacy in this treatment is unknown and possibly doubtful.
It also contains several furostanol and spirostanol glycosides, amongst which are Sitosterol and Stigmasterol and their glycosides. A spiro-furostanol saponin called sarsapogenin is present which exhibits spermicidal activity. Altogether, about twelve spirostanols are known to occur in Asparagus, and which exist throughout the plant.
ASPARGINE & ACRYLAMIDE
L-Asparagine (compare with Aspartic Acid) is one of the 20 common (22 now) naturally occurring, but non-essential, amino acids and the first to be discovered, and it was discovered in Asparagus in 1806. As an amino acid, it constitutes part of the backbone of some proteins. Reactions between asparagine and reducing sugars are responsible for the un-wanted creation of toxic acrylamides during the high temperature cooking of food, as occurs when baking, grilling or toasting starch-containing foodstuffs. Acrylamides are thus present in bread, chips, crisps, baked potatoes and other baked products probably including fried rice. Acrylamide does not occur naturally in asparagus. Acrylamide is a carcinogen and it is advisable that cooks try to minimise the amount that might be produced during the high-temperature cooking of some foods.
A BETAINE & NON-PRTOEINOGENIC AMINO ACID
Carnitine (not to be confused with
Carnosine) is both a Betaine, a Non-Proteinogenic Amino Acid (NPAA) and a quaternary ammonium compound. It appears that it was originally found as a growth hormone for mealworms, but the Author suspects that Asparagus is synthesising it for some other purpose than to encourage the growth of insects which may eat it. As a result of its growth factor involvement (at least in mealworms) Carnitine has been labelled as Vitamin BT although it is not a true vitamin. Carnitine is also found within animals where it is required by the mitochondria within cells, mainly in the liver.
The natural form consists only of the L-isomer, the D-isomer is biologically inactive. It is found at highish concentrations within meat such as beef (1000ppm), pork (270ppm) and chicken (40ppm) and is also present to a much lesser extent in milk (3ppm), asparagus, white bread, macaroni rice eggs and orange juice, the latter containing just trace amounts (2ppb), all by weight. It is marketed as a weight loss supplement despite the fact that there is no evidence of any effectiveness.
Pharmaceutically, L-Carnitine (or Propionyl-L-Carnitine) is primarily administered for those with heart-related conditions such as angina, but is of no use for heart-attack patients.
It is also prescribed by those on kidney dialysis because kidney disease usually results in a deficiency of L-Carnitine.
It is thought that it should be helpful in the treatment of Valproic Acid poisoning, the salts of which are used a pharmaceutically as an anti-convulsant and mood stabiliser, but this idea has not been tested in the field. It has been established as effective in the treatment of hyperthyroidism, some tissues of which are short of carnitine in those possessing the disease.