Digitalis lanata

Digitalis lanata, vernacularly often called woolly foxglove[3] or Grecian foxglove,[4] is a species of foxglove, a flowering plant in the plantain family Plantaginaceae. It gets its name due to the woolly indumentum of the leaves. D. lanata, like other foxglove species, is toxic in all parts of the plant. Symptoms of digitalis poisoning include nausea, vomiting, severe headache, dilated pupils, problems with eyesight, and convulsions at the worst level of toxicity. The plant is also harmful to other animals.[5]

Digitalis lanata
flowering in situ on the island of Thasos, Greece
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Lamiales
Family: Plantaginaceae
Genus: Digitalis
Species:
D. lanata
Binomial name
Digitalis lanata
Ehrh., 1792[1]
Synonyms[2]
  • Digitalis epiglottidea Brera ex Steud.
  • Digitalis eriostachya Besser ex Rchb.
  • Digitalis nova Winterl ex Lindl.
  • Digitalis orientalis Elmig.
  • Digitalis winterli Roth

A vernacular name in Greek is διγιτάλης η εριώδης, 'digitális i eriódis'.[6]

Description

Digitalis lanata is a biennial or perennial growing from a woody, horizontal rootstock.[7] There is a tidy rosette before the spike goes up, and it is neatly arranged around the purple-tinged stems. The plant commonly forms a single, upright, more or less uniformly leafy stem that is partly ascending at the base.[7] The plant send up these stems and flowers in usually in its second year.[4][5] The stems are 0.3 to 0.6 meters in height, or about 13 to 26 inches.[7]

The leaves are moderately green in colour, woolly, veined, and covered with white hairs on the underside. They have a very bitter taste. The lower cauline leaves are 6 to 12 cm (sometimes to 20 cm) long and 1.5 to 3.5 cm wide, the upper cauline leaves are 4 to 10 cm long and lanceolate shaped, usually with entire margins, and with a distinctive mid-rib.[7] The leaves along the stalks are alternate.[5] The lower stem leaves wither by early flowering.[7] Both flowers and stems are also woolly or hairy.

The inflorescence axis is densely covered with densely matted woolly hairs (tomentose), and the flowers are densely arranged into a raceme that is pyramidal in shape.[7] The flowers are tubular and bell shaped, pale yellow to whitish with brown or violet lines (ferruginous reticulated markings),[8] and the centre lobe of the lower lip is 8 to 13 mm long.[9]

The fruit is a conical capsule with a blunt end topped by a short beak. The seeds which develop within are quadrangular or prismatic in shape, and are about 0.6mm broad and 1.1 to 1.3mm long.[7]

Distribution

It is native to Anatolia and the Balkans, where it is found in Albania, Bulgaria, Croatia, Greece, Thrace (European Turkey), Hungary, Serbia, Kosovo and Romania,[6] eastwards to northern Moldova. It has been introduced to Ukrainian Galicia,[6][7] Austria, the Czech Republic, Estonia and Germany. Its presence in Slovakia is questionable.[6]

In the US it has naturalised in a number of northeastern states. Although it has yet only spread to a few counties per state, it is still considered potentially invasive or a noxious weed. The state of Minnesota considers it a noxious weed,[5][10] and it is an invasive species of grasslands and woodlands in Wisconsin,[11] and Kansas. As of 2001, it may not be imported into Kansas.[4] It has also naturalised in the US states of Connecticut, Indiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Nebraska, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Vermont and West Virginia. In Canada it has become naturalised in southern Ontario and Quebec.[2] Other areas where it might be naturalised are Vietnam and the western Himalayas.[2]

Taxonomy

Although it has in recent times been placed in the plantain family, Plantaginaceae, a family of flowering plants included in the order Lamiales,[2] it was generally placed in the Scrophulariaceae in the last few centuries, but has also been placed in the Veronicaceae.

The generic epithet Digitalis comes from the Latin word digitus, which means finger.[12] The word lanatus means 'woolly'.

Ecology

In Minnesota it is in leaf all year, in flower in June and July, and the seeds ripen in early-mid September.[5] The flowers are perfect (having both male and female organs). Bees pollinate the flowers. In the Ukraine and Moldova it flowers in July and August.[7]

The species is adapted to sunny and warm sites. It prefers part shade and humus-rich soil, but also grows in sandy,[13] stony loamy, and clay soils under dry or moist conditions.

During the first vegetation period, only the leaf rosette is developed, flowering follows during the second vegetation period. Therefore, especially during the first year, there is a high resistance against drought stress. The leaves remain somewhat turgid even under very low leaf water potential, due to osmotic adaptation by synthesis of non-ionic substances in the leaves. The drought induced diminishing of photosynthesis is reversible after a few hours following watering of the plants.[14] Drought stress also reduces the quantum yield of photosystem 2.[15] More than 70 bitter glycosides with cardiac activity, with five different aglyconees digitoxigenin, gitoxigenin, digoxigenin, diginatigenin and gitaloxigenin in the leaves act as a protection against herbivores.[16] Yield and concentration of these cardiac glycosides are enhanced by greenhouse cultivation through enhanced temperature and enhanced carbon dioxide concentration.[17]

Uses

Medical

Digitalis lanata contains a powerful cardiac glycoside that may be used by patients with heart conditions. Digoxin (digitalin) is a drug that is extracted from D. lanata.[18][19] It is used to treat some heart conditions such as atrial fibrillation and cardiac arrhythmias.[19] Its cardiotonic effects slows atrioventricular conduction so that the heartbeat slows down and slightly increases contraction power (positive inotropic effect).[20] Because of the improved circulation in congestive heart failure caused by fast atrial fibrillation, the kidneys can function better, which stimulates the flow of urine, which lowers the volume of the blood and lessens the load on the heart.

The medical uses of Digitalis glycosides in veterinary care has been controversial because of its relatively low therapeutic to toxicity profile, divergent physiological responses, variation in side effects, and the difficulty in demonstrating positive therapeutic responses.[20]

Cardiac glycosides from D. lanata and other natural sources have toxic effects, producing ventricular automaticity and vagal effects, resulting in AV nodal blocking. Acute toxicity produces nausea, vomiting, lethargy, confusion, and weakness.[21]

William Withering is credited as the first to clinically investigate the plant as a therapy for dropsy, writing a book in 1785 about the potential medical uses of D. purpurea extracts after his human trials.[22][23]

Digitalin was not discovered until the mid-19th century by two French scientists Homolle Ouevenne and Theodore Ouevenne. It was not until 1875 that Oscar Schmiedberg identified digoxin in the plant.[24] It was first isolated in the 1930s in Britain by Sydney Smith.[25] Today it is still extracted from the plant because industrial synthesis is too expensive and difficult.[23] However, it is becoming less frequently used[22] due to the narrow therapeutic margin[20] and high potential for severe side effects.[21] Digoxin is being replaced by newer drugs[22] including beta blockers, angiotensin-converting enzyme inhibitors, and the calcium channel blocking agents. As new pharmacotherapeutic agents arise, the use of digitalis preparations is expected to continue to decline.

Asylums used digitalis extracts throughout the 19th century as sedatives along with hyoscine and opiates.[26]

The commercial production of digoxin from D. lanata involves growing the plant from seed for two years, harvesting and drying it in a silo, then the leaves are crushed into a powder, and the compound is extracted and purified using chemical processes.[27]

Other

Digoxigenin (DIG) is a steroid found in the flowers and leaves of Digitalis species, and is extracted from D. lanata. Digoxigenin can be used as a molecular probe to detect mRNA in situ and label DNA, RNA, and oligonucleotides.[28] It can easily be attached to nucleotides such as uridine by chemical modifications. DIG molecules are often linked to nucleotides; DIG-labelled uridine can then be incorporated into RNA via in vitro transcription. Once hybridisation occurs, RNA with the incorporated DIG-U can be detected with anti-DIG antibodies conjugated to alkaline phosphatase. To reveal the hybridised transcripts, a chromogen can be used which reacts with the alkaline phosphatase to produce a coloured precipitate.

Pictures

References
  1. "Digitalis lanata". International Plant Names Index. The Royal Botanic Gardens, Kew, Harvard University Herbaria & Libraries and Australian National Botanic Gardens. Retrieved 30 November 2020.
  2. "Digitalis lanata Ehrh". Plants of the World Online. Royal Botanic Gardens, Kew. 2017. Retrieved 30 November 2020.
  3. Elizabeth A. Dauncey; Sonny Larsson (6 March 2018). Plants That Kill: A Natural History of the World's Most Poisonous Plants. Princeton University Press. pp. 199–. ISBN 978-0-691-17876-9.
  4. "Grecian Foxglove". Biological Control and Eradication Projects. Kansas Department of Agriculture. 2006. Archived from the original on 2010-08-24. Retrieved 2010-05-06.
  5. "Grecian foxglove (Digitalis lanata)". Terrestrial invasive species. Minnesota Department of Natural Resources. 2020. Retrieved 6 December 2020.
  6. Marhold, Karol (2011). Greuter, Werner; von Raab-Straube, E. (eds.). "Details for: Digitalis lanata". Euro+Med Plantbase. Botanic Garden and Botanical Museum Berlin-Dahlem. Retrieved 30 November 2020.
  7. Ivanina, L. I. (1997) [1955]. Schischkin, B. K.; Bobrov, E. G. (eds.). Flora of the U.S.S.R. 22. Translated by Bakaya, Kamal. Springfield, Va.: Israel Program for Scientific Translations. p. 461.
  8. John Sims (1821). Curtis's Botanical Magazine, Or, Flower-garden Displayed: In which the Most Ornamental Foreign Plants, Cultivated in the Open Ground, the Green-house, and the Stove, are Accurately Represented in Their Natural Colours ... pp. 271–.
  9. Ann Fowler Rhoads; Timothy A. Block (5 September 2007). The Plants of Pennsylvania: An Illustrated Manual. University of Pennsylvania Press. p. 787. ISBN 978-0-8122-4003-0.
  10. Minnesota. Legislature. Senate (2002). Journal of the Senate. p. 6503.
  11. Invasiveness Ranking System for Non-native Plants of Alaska. U.S. Department of Agriculture, Forest Service, Alaska Region. 2008. pp. 2–.
  12. Hollman, A (September 1985). "Plants and cardiac glycosides". Br. Heart Journal. 54 (3): 258–261. doi:10.1136/hrt.54.3.258. PMC 481893. PMID 4041297.
  13. Ken Druse (14 April 2015). The New Shade Garden: Creating a Lush Oasis in the Age of Climate Change. Abrams. pp. 344–. ISBN 978-1-61312-604-2.
  14. Stuhlfauth, T; Sultemeyer, D. F; Weinz, S; Fock, H. P (1988). "Fluorescence Quenching and Gas Exchange in a Water Stressed C3 Plant, Digitalis lanata". Plant Physiology. 86 (1): 246–250. doi:10.1104/pp.86.1.246. PMC 1054462. PMID 16665875.
  15. Fock, H.P.; Biehler, K.; Stuhlfauth, T. (1992). "Use and degradation of light energy in water-stressed Digitalis lanata". Photosynthetica. 27 (4): 571–7.
  16. Hildebert Wagner, Pharmazeutische Biologie, 2. Drogen und ihre Inhaltsstoffe, Gustav Fischer Verlag, Stuttgart 1980
  17. Stuhlfauth, T; Fock, H. P (1990). "Effect of Whole Season CO2 Enrichment on the Cultivation of a Medicinal Plant, Digitalis lanata". Journal of Agronomy and Crop Science. 164 (3): 168–173. doi:10.1111/j.1439-037X.1990.tb00803.x.
  18. Hollman, A (1996). "Digoxin comes from Digitalis lanata". BMJ. 312 (7035): 912. doi:10.1136/bmj.312.7035.912. PMC 2350584. PMID 8611904.
  19. Peter Harris; Sue Nagy; Nicholas Vardaxis (22 August 2018). Mosby's Dictionary of Medicine, Nursing and Health Professions - Revised 3rd Anz Edition. Elsevier Health Sciences. pp. 527–. ISBN 978-0-7295-8691-7.
  20. Deborah Silverstein; Kate Hopper (13 February 2008). Small Animal Critical Care Medicine - E-Book. Elsevier Health Sciences. pp. 98–. ISBN 978-1-4160-6926-3.
  21. Daniel M Lugassy (9 February 2014). Clinical Toxicology, An Issue of Emergency Medicine Clinics of North America, E-Book. Elsevier Health Sciences. pp. 88–. ISBN 978-0-323-26655-0.
  22. Weisse, Allen B. (January 2010). "A Fond Farewell to the Foxglove? The Decline in the Use of Digitalis". Journal of Cardiac Failure. 16 (1): 45–48. doi:10.1016/j.cardfail.2009.08.001. PMID 20123317.
  23. Kreis, Wolfgang (2017). "The Foxgloves (Digitalis) Revisited". Planta Medica. 83 (12–13): 962–976. doi:10.1055/s-0043-111240. PMID 28561136.
  24. G. Dragendorff (1884). Plant Analysis Qualitative & Quantitative. London: Bailliere, Tindall and Cox. p. 142.
  25. Sydney Smith III (1931). "Digitalis glucosides". Journal of the Chemical Society. 23 (3).
  26. Healy, David (2002). The Creation of Psychopharmacology. LONDON, ENGLAND: HARVARD UNIVERSITY PRESS. p. 43. ISBN 0-674-01599-1.
  27. http://www.buffalo.edu/news/releases/2020/04/013.html
  28. Bernard R. Glick (4 May 2018). Methods in Plant Molecular Biology and Biotechnology. CRC Press. pp. 183–. ISBN 978-1-351-09139-8.

Further reading
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