View source for Digitalis

{{Redirect|Foxglove}}
{{italictitle}}
{{taxobox
|name = Foxglove
|image = Digitalis purpurea2.jpg
|image_caption = ''Digitalis purpurea'' (Common Foxglove)
|regnum = [[Plantae]]
|unranked_divisio = [[Angiosperms]]
|unranked_classis = [[Eudicots]]
|unranked_ordo = [[Asterids]]
|ordo = [[Lamiales]]
|familia = [[Plantaginaceae]]<ref name="olmstead">{{cite journal | author = Olmstead, R. G., dePamphilis, C. W., Wolfe, A. D., Young, N. D., Elisons, W. J. & Reeves P. A. | title = Disintegration of the Scrophulariaceae | journal= American Journal of Botany| volume= 88| pages = 348–361| year=2001 | url = http://www.amjbot.org/cgi/content/full/88/2/348  | doi = 10.2307/2657024 | pmid = 11222255 | issue = 2 | jstor = 2657024 | publisher = American Journal of Botany, Vol. 88, No. 2}}</ref>
|genus = '''''Digitalis'''''
|genus_authority = [[Carolus Linnaeus|L.]]
|subdivision_ranks = Species
|subdivision = About 20 species, including:<br/>
''[[Digitalis cariensis]]''<br/>
''[[Digitalis ciliata]]''<br/>
''[[Digitalis davisiana]]''<br/>
''[[Digitalis dubia]]''<br/>
''[[Digitalis ferruginea]]''<br/>
''[[Digitalis grandiflora]]''<br/>
''[[Digitalis laevigata]]''<br/>
''[[Digitalis lanata]]''<br/>
''[[Digitalis leucophaea]]''<br/>
''[[Digitalis lutea]]''<br/>
''[[Digitalis obscura]]''<br/>
''[[Digitalis parviflora]]''<br/>
''[[Digitalis purpurea]]''<br/>
''[[Digitalis thapsi]]''<br/>
''[[Digitalis trojana]]''<br/>
''[[Digitalis viridiflora]]''
|}}

'''''Digitalis''''' ({{pron-en|ˌdɪdʒɨˈteɪlɨs}}<ref>''[[OED]]:'' "Digitalis"</ref> or {{IPA|/ˌdɪdʒɨˈtælɨs/}}<ref>[http://dictionary.reference.com/browse/digitalis Digitalis] at Dictionary.com]</ref>) is a genus of about 20 species of [[herb]]aceous [[Perennial plant|perennials]], shrubs, and [[Biennial plant|biennials]] that are commonly called '''foxgloves'''. This genus was traditionally placed in the figwort family [[Scrophulariaceae]], but upon recent reviews of [[phylogenetic]] research, it has now been placed in the much enlarged family [[Plantaginaceae]].<ref name="olmstead"/> This genus is native to western and south western Europe,<ref name="Arkive"> cite web|url=http://www.arkive.org/foxglove/digitalis-purpurea/range-and-habitat.html|title=Foxglove (Digitalis purpurea)|last=Anon|work=Arkive: images of life on Earth|publisher=Wildscreen|accessdate=6 May 2010}}</ref> western and central Asia, and northwestern Africa. The scientific name means "finger-like" and refers to the ease with which a [[flower]] of ''Digitalis purpurea'' can be fitted over a human fingertip. The flowers are produced on a tall spike, are tubular, and vary in colour with species, from purple to pink, white, and yellow. The best-known species is the "Common Foxglove", ''[[Digitalis purpurea]]''. This is a [[biennial plant]] which is often grown as an [[ornamental plant]] due to its vivid [[flower]]s. These range in color from various purple [[tint]]s through various shades of light gray, and to purely white. The flowers can also possess various marks and spottings. 

The first year of growth of the Common Foxglove produces only the stem with its long, basal leaves. During the second year of the plant's life, a long leafy stem from 50 to 250 [[centimeter]]s tall grows atop the roots of healthy plants.

The [[larva]]e of the insect the "[[Foxglove pug]]" consume the flowers of the Common Foxglove for food. Other species of [[Lepidoptera]] eat the leaves of the Common Foxglove, including [[Lesser Yellow Underwing]].

The term '''digitalis''' is also used for [[drug]] preparations that contain [[cardiac glycoside]]s, particularly one called [[digoxin]], that are extracted from various plants of this genus.

==Etymology ==
There have been many suggestions for the derivation of the name "foxglove". According to the 19th century book, ''English Botany, Or, Coloured Figures of British Plants'':
<blockquote>
Dr. Prior, whose authority is great in the origin of popular names, says "It seems probably that the name was in the first place, ''foxes' glew'', or music, in reference to the favourite instrument of an earlier time, a ring of bells hung on an arched support, the ''tintinnabulum''"... we cannot quite agree with Dr. Prior for it seems quite probable that the shape of the flowers suggested the idea of a glove, and that associated with the name of the botanist ''Fuchs'', who first gave it a botanical name, may have been easily corrupted into ''foxglove''. It happens, moreover, the name ''foxglove'' is a very ancient one and exists in a list of plants as old as the time of Edward III. The "folks" of our ancestors were the fairies and nothing is more likely than that the pretty coloured bells of the plant would be designated "''folksgloves''," afterwards, "foxglove." In Wales it is declared to be a favourite lurking-place of the fairies, who are said to occasion a snapping sound when children, holding one end of the digitalis bell, suddenly strike the other on the hand to hear the clap of fairy thunder, with which the indignant fairy makes her escape from her injured retreat. In south of Scotland it is called "bloody fingers" more northward, "deadman's bells" whilst in Wales it is known as "fairy-folks-fingers" or "lambs-tongue-leaves."<ref>{{cite book|last=Lankester|first=Mrs.|others=Sowerby J, Smith C, Johnson J.E, Salter J.W.|title=English Botany, Or, Coloured Figures of British Plants (full text)|editor=Boswell J.T.|publisher=Edward hardwicke|location=London|date=1866|edition=III|volume=VI campanulacae to verbanacea|pages=128|url=http://books.google.com/?id=V0cAAAAAQAAJ&pg=PA128&dq=foxglove+finger+like&cd=3#v=onepage&q=foxglove%20finger%20like}}</ref>
</blockquote>

== Habitat ==
Digitalis thrives in acidic soils, in partial sunlight to deep shade, in a range of habitats including open woods, woodland clearings, moorland, and heath margins, sea-cliffs, rocky mountain slopes and hedgebanks.<ref name="Arkive" /><ref>{{cite web|url=http://aggie-horticulture.tamu.edu/wildseed/27/27.4.html|title=Foxglove: Digitalis purpurea (Scrophulariaceae)|last=Anon|work=Wildflowers in Bloom|publisher=Wildseed farms|accessdate=7 May 2010}}</ref> It is commonly found on sites where the ground has been disturbed, such as recently cleared woodland, or where the vegetation has been burnt.<ref>{{cite news|url=http://www.telegraph.co.uk/gardening/howtogrow/3300521/How-to-grow-Foxgloves.html|title=How to grow: Foxgloves|last=Klein|first=Carol|date=18 May 2002|work=The Telegraph|publisher=Telegraph Media Group Limited |accessdate=6 May 2010|location=London, UK}}</ref>

== Medicinal use ==
A group of medicines extracted from foxglove plants are called "Digitalin". The use of ''[[Digitalis purpurea]]'' extract containing [[cardiac glycoside]]s for the treatment of [[heart]] conditions was first described in the English speaking medical literature by [[William Withering]], in 1785,<ref>{{cite journal|author=Goldthorp WO|title=Medical Classics: An Account of the Foxglove and Some of its Medicinal Uses by William Withering, published 1785|journal=Brit Med J|year=2009|volume=338|pages=b2189}}</ref> which is considered the beginning of modern therapeutics (Silverman)<ref name=Silverman>. In contemporary [[medicine]], a purer form of digitalis (usually [[digoxin]]) is obtained from ''Digitalis lanata.''</ref><ref name=Hollman>Digoxin comes from Digitalis lanata. Hollman A. ''BMJ'' 1996;312:912. online version accessed 18 Oct 2006 
[http://bmj.bmjjournals.com/cgi/content/full/312/7035/912]</ref>  It is used to increase cardiac contractility (it is a positive [[inotrope]]) and as an [[antiarrhythmic agent]] to control the heart rate, particularly in the irregular (and often fast) [[atrial fibrillation]]. Digitalis is hence often prescribed for patients in atrial fibrillation, especially if they have been diagnosed with [[congestive heart failure]].

A group of pharmacologically active compounds are extracted mostly from the leaves of the second year's growth, and in pure form are referred to by common chemical names such as '''''[[digitoxin]]''''' or '''''[[digoxin]]''''', or by brand names such as ''Crystodigin'' and ''Lanoxin'', respectively. The two drugs differ in that Digoxin has an additional [[hydroxyl]] group at the C-3 position on the B-ring (adjacent to the pentane). Both molecules include a [[lactone]] and a triple-repeating [[sugar]] called a [[glycoside]].

Digitalis works by inhibiting [[sodium-potassium ATPase]]. This results in an increased intracellular concentration of sodium, which in turn increases intracellular [[calcium]] by passively decreasing the action of the [[sodium-calcium exchanger]] in the [[Endoplasmic reticulum#Sarcoplasmic reticulum|sarcoplasmic reticulum]]. The increased intracellular calcium gives a positive [[inotropic]] effect.
Digitalis also has a vagal effect on the [[parasympathetic nervous system]], and as such is used in reentrant [[cardiac arrhythmia]]s and to slow the ventricular rate during [[atrial fibrillation]]. The dependence on the vagal effect means that digitalis is not effective when a patient has a high [[sympathetic nervous system]] drive, which is the case with acutely ill persons, and also during exercise.

Digitalis toxicity (''Digitalis intoxication'') results from an overdose of digitalis and causes anorexia, nausea, vomiting and diarrhea, as well as sometimes resulting in [[xanthopsia]] (jaundiced or yellow vision) and the appearance of blurred outlines (halos). [[Bradycardia]] also occurs.  Because a frequent side effect of digitalis is reduction of appetite, some individuals have used the drug as a weight loss aid.

Digitalis is an example of a drug that is derived from a plant that was formerly used by [[folklorist]]s and [[herbalist]]s: herbalists have largely abandoned its use because of its narrow [[therapeutic index]] and the difficulty of determining the amount of active drug in herbal preparations. Once the usefulness of digitalis in regulating the human [[pulse]] was understood, it was employed for a variety of purposes, including the treatment of [[epilepsy]] and other seizure disorders, which are now considered to be inappropriate treatments.

== Toxicity ==
{{see main|Digoxin toxicity}}
[[Image:Digitalis purpurea Koehler drawing.jpg|thumb|right|''Digitalis purpurea'' drawings by [[Köhler's Medicinal Plants|Franz Köhler]]]]
Depending on the species, the digitalis plant may contain several deadly physiological and chemically related [[cardiac glycosides|cardiac]] and [[steroidal glycosides]]. Thus, the digitalis has earned several more sinister names: ''Dead Man’s Bells'', and ''Witches’ Gloves''. 

The entire plant is toxic (including the roots and seeds), although the leaves of the upper stem are particularly potent, with just a nibble being enough to potentially cause death. Early symptoms of ingestion include [[nausea]], [[vomiting]], [[diarrhea]], abdominal pain, wild hallucinations, [[delirium]], and severe headache. Depending on the severity of the toxicosis the victim may later suffer irregular and slow pulse, [[tremors]], various cerebral disturbances, especially of a visual nature (unusual colour visions with objects appearing yellowish to green, and blue halos around lights), [[convulsions]], and deadly disturbances of the heart.  For a case description, see the paper by Lacassie.<ref name=Lacassie>A non-fatal case of intoxication with foxglove, documented by means of liquid chromatography-electrospray-mass spectrometry. Lacassie E et al., ''J Forensic Sci.'' 2000 Sep;45(5):1154-8. Abstract accessed online 19 Sep 2006. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=11005196&query_hl=13&itool=pubmed_DocSum]</ref>

There have been instances of people confusing digitalis with the relatively harmless ''[[Symphytum]]'' (comfrey) plant (which is often brewed into a tea) with fatal consequences. Other fatal accidents involve children drinking the water in a vase containing digitalis plants. Drying does not reduce the toxicity of the plant. The plant is toxic to animals including all classes of livestock and poultry, as well as felids and canids.

Digitalis poisoning can cause [[heart block]] and either [[bradycardia]] (lowered heart rate) or  [[tachycardia]] (increased heart rate), depending on the dose and the condition of one's heart. It should however be noted, that electric cardioversion (to "shock" the heart) is generally not indicated in ventricular fibrillation in digitalis toxicity, as it can increase the dysrhythmia in digitalis toxicity{{Fact|reason=Who cardioverts a VFib? Do you mean defibrillation instead of cardioversion or VTach instead of VFib?|date=May 2009}}. Also, the classic drug of choice for VF (ventricular fibrillation) in emergency setting,<ref>{{cite web |url=http://www.erc.edu |title=European Resuscitation Council}}{{Verify source|date=December 2008}}</ref> [[amiodarone]], can worsen the dysrhythmia caused by digitalis, therefore, the second-choice drug [[Lidocaine]] is more commonly used.{{Fact|date=January 2008}}

== Digoxigenin ==

[[Digoxigenin]] (DIG) is a steroid found exclusively in the flowers and leaves of the plants ''[[Digitalis purpurea]]'' and ''[[Digitalis lanata]]''. It is used as a molecular probe to detect DNA or RNA. It can easily be attached to nucleotides by chemical modifications. DIG molecules are often linked to [[uridine]] [[nucleotides]]; DIG labeled [[uridine]] (DIG-U) can then be incorporated into [[RNA]] probes via [[in vitro transcription]]. Once [[Nucleic acid hybridization|hybridisation]] occurs ''in situ'', [[RNA]] probes with the incorporated DIG-U can be detected with anti-DIG [[antibodies]] that are conjugated to [[alkaline phosphatase]]. To reveal the hybridised transcripts, [[alkaline phosphatase]] can be reacted with a [[chromogen]] to produce a colour precipitate.
[[Image:Digitalis lutea 100705.jpg|thumb|right|''[[Digitalis lutea]]'']]

==See also==
* [[List of plants poisonous to equines]]

==Footnotes==
{{reflist}}

==References==
*Richard B. Silverman, The Organic Chemistry of Drug Design and Drug Action.
*''Flora of Turkey''. Edinburgh University Press.

==External links==
{{Commons|Digitalis|''Digitalis''}}
{{Wiktionarypar|digitalis}}
*[http://rbg-web2.rbge.org.uk/cgi-bin/nph-readbtree.pl/feout?FAMILY_XREF=&GENUS_XREF=Digitalis&SPECIES_XREF=&TAXON_NAME_XREF=&RANK=species Flora Europaea: ''Digitalis'' species list]
*[http://www.bris.ac.uk/Depts/Chemistry/MOTM/digitalis/digtalis.htm Molecule of the Month - Digitalis]
*[http://www.emedicine.com/PED/topic590.htm eMedicine link]
*[http://plants.usda.gov/java/profile?symbol=DILA3 Grecian Foxglove] USDA Noxious Weed List.
*[http://plants.usda.gov/java/profile?symbol=DIPU Purple Foxglove] USDA Noxious Weed List.

[[Category:Antiarrhythmic agents]]
[[Category:Medicinal plants]]
[[Category:Plantaginaceae]]
[[Category:Poisonous plants]]

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