Digitalis
Digitalis is a genus of about 20 species of herbaceous perennial plants, shrubs, and biennials, commonly called foxgloves.
Digitalis is native to Europe, Western Asia, and northwestern Africa. The flowers are tubular in shape, produced on a tall spike, and vary in colour with species, from purple to pink, white, and yellow. The name derives from the Latin word for "finger". The genus was traditionally placed in the figwort family, Scrophulariaceae, but phylogenetic research led taxonomists to move it to the Veronicaceae in 2001. More recent phylogenetic work has placed it in the much enlarged family Plantaginaceae.
The best-known species is the common foxglove, Digitalis purpurea. This biennial is often grown as an ornamental plant due to its vivid flowers, which range in colour from various purple tints through pink and pure white. The flowers can also possess various marks and spottings. Other garden-worthy species include D. ferruginea, D. grandiflora, D. lutea, and D. parviflora.
The term digitalis is also used for drug preparations that contain cardiac glycosides, particularly one called digoxin, extracted from various plants of this genus. Foxglove has medicinal uses but is also very toxic to humans and other mammals, such that consumption can cause serious illness or death.
Etymology
The generic epithet Digitalis is from the Latin digitus. Leonhart Fuchs first invented the name for this plant in his 1542 book De historia stirpium commentarii insignes, based upon the German vernacular name Fingerhut, which translates literally as 'finger hat', but actually means 'thimble'.The name is recorded in Old English as 'foxes glofe/glofa' or 'fox's glove'. Over time, folk myths obscured the literal origins of the name, insinuating that foxes wore the flowers on their paws to silence their movements as they stealthily hunted their prey. The woody hillsides where the foxes made their dens were often covered with the toxic flowers. Some of the more menacing names, such as "witch's glove", reference the toxicity of the plant.
Henry Fox Talbot proposed 'folks' glove', where 'folk' means fairy. Similarly, R. C. A. Prior suggested an etymology of 'foxes-glew', meaning 'fairy music'. However, neither of these suggestions account for the Old English form foxes glofa.
Taxonomy
It was published by Carl Linnaeus in 1753. The lectotype species Digitalis purpurea L. was designated in 1930.Species
The Flora Europaea originally recognised a number of species now seen as synonyms of Digitalis purpurea, or others: D. dubia, D. leucophaea, D. micrantha and D. trojana. As of 2017, Plants of the World Online recognises the following 27 species :- Digitalis atlantica Pomel
- Digitalis canariensis L.
- Digitalis cariensis Boiss. ex Jaub. & Spach
- Digitalis cedretorum Maire
- Digitalis chalcantha Albach, Bräuchler & Heubl
- Digitalis ciliata Trautv.
- Digitalis davisiana Heywood
- Digitalis ferruginea L.
- Digitalis fuscescens Waldst. & Kit.
- Digitalis grandiflora Mill.
- Digitalis ikarica Strid
- Digitalis isabelliana Linding.
- Digitalis laevigata Waldst. & Kit.
- Digitalis lamarckii Ivanina
- Digitalis lanata Ehrh.
- Digitalis lutea L.
- Digitalis mariana Boiss.
- Digitalis minor L.
- Digitalis nervosa Steud. & Hochst. ex Benth.
- Digitalis obscura L.
- Digitalis parviflora Jacq.
- Digitalis purpurea L.
- Digitalis sceptrum L.f.
- Digitalis subalpina Braun-Blanq.
- Digitalis thapsi L.
- Digitalis transiens Maire
- Digitalis viridiflora Lindl.
Hybrids
- Digitalis × coutinhoi Samp.
- Digitalis × fulva Lindl.
- Digitalis × macedonica Heywood
- Digitalis × media Roth
- Digitalis × pelia Zerbst & Bocquet
- Digitalis × purpurascens Roth
- Digitalis × sibirica Werner had been considered a valid species since it was first described by the English botanist and gardener John Lindley in 1821, but it was considered a hybrid of D. grandiflora and D. laevigata by the German botanist in 1960.
Systematics
In the last full monograph of the genus in 1965, Werner classified the 19 recognised species in five sections :
- In the section Digitalis, along with the type species D. purpurea, four other species were placed: D. thapsi, D. dubia, D. heywoodii and D. mariana.
- The monotypic section Frutescentes contained only D. obscura.
- The section Grandiflorae, which was also called section Macranthae by Vernon Hilton Heywood. It included, along with the type species D. grandiflora, also D. atlantica, D. ciliata and D. davisiana.
- Globiflorae included five species: D. laevigata, D. nervosa, D. ferruginea, D. cariensis and D. lanata.
- Tubiflorae included four species: D. subalpina, D. lutea, D. viridiflora and D. parviflora.
Peter Hadland Davis, an expert on the flora of Turkey, had used a different circumscription than Werner in his works, and recognised eight species in the country. A 2016 molecular phylogenetic study into the relationships of the Turkish species in the section Globiflorae aimed to reconcile this discrepancy, finding that the classification as proposed by Davis was largely correct: Globiflorae contained as distinct species D. cariensis, D. ferruginea, D. lamarckii, D. lanata and D. nervosa, and D. trojana was subsumed at the infraspecific rank as D. lanata subsp. trojana. This study listed 23 species: D. transiens, D. cedretorum, D. ikarica and D. fuscescens were not mentioned. D. parviflora and D. subalpina were not tested in this study, but the 2004 study found these two species situated within the section Globiflorae.
Ecology
e of the foxglove pug, a moth, consume the flowers of the common foxglove for food. Other species of Lepidoptera eat the leaves, including the lesser yellow underwing. The shape of the foxglove's flowers makes it especially attractive to long-tongued bees, such as the common carder bee. The bright flowers attract the bee, which lands on the lower lip of the bloom before climbing up the tube. This means that the bee is likely to drop any pollen it may have collected from other foxgloves, thereby facilitating propagation.Uses
Historical uses
included Foxglove in his 1652 herbal medicine guide, The English Physician. He cited its use for healing wounds, as a purgative, for "the King's Evil", for "the falling sickness", and for "a scabby head". There is no empirical evidence for these claims, and it is not used for these conditions in modern medicine, only for slowing excessive heart rate in certain circumstances and/or strengthening heart muscle contraction in heart failure.Medicinal uses
Digitalis is an example of a drug derived from a plant that was formerly used by herbalists; 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.A group of medicines extracted from foxglove plants are called digitalin. The use of D. purpurea extract containing cardiac glycosides for the treatment of heart conditions was first described in the English-speaking medical literature by William Withering, in 1785, which is considered the beginning of modern therapeutics. In contemporary medicine, digitalis is obtained from D. lanata. It is used to increase cardiac contractility and as an antiarrhythmic agent to control the heart rate, particularly in the irregular atrial fibrillation. Digitalis is hence often prescribed for patients in atrial fibrillation, especially if they have been diagnosed with congestive heart failure. Digoxin was approved for heart failure in 1998 under current regulations by the Food and Drug Administration on the basis of prospective, randomized study and clinical trials. It was also approved for the control of ventricular response rate for patients with atrial fibrillation. American College of Cardiology/American Heart Association guidelines recommend digoxin for symptomatic chronic heart failure for patients with reduced systolic function, preservation of systolic function, and/or rate control for atrial fibrillation with a rapid ventricular response. Heart Failure Society of America guidelines for heart failure provide similar recommendations. Despite its relatively recent approval by the Food and Drug Administration and the guideline recommendations, the therapeutic use of digoxin is declining in patients with heart failure—likely the result of several factors. The main factor is the more recent introduction of several drugs shown in randomised controlled studies to improve outcomes in heart failure. Safety concerns regarding a proposed link between digoxin therapy and increased mortality seen in observational studies may have contributed to the decline in therapeutic use of digoxin, however a systematic review of 75 studies including four million patient years of patient follow-up showed that in properly designed randomised controlled studies, mortality was no higher in patients given digoxin than in those given placebo.
Romani people use foxglove to treat eczema.