Leonotis leonurus (Lamiaceae) by Manton Hirst (PhD) & Michael Knott (B. Pharm, MSc)
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Leonotis leonurus (Lamiaceae)
by Manton Hirst (PhD) & Michael Knott (B. Pharm, MSc)

L. leonurus (L.) R. Br. has a variety of colourful common names: Cape hemp, wild dagga (hemp), lion's ear, minaret flower, koppiesdagga (Afrikaans), rooidagga, wildedagga, duiwelstabak (devil’s tobacco), umfincafincane (Xhosa), imunyane (Zulu) and lebake (Sotho).6  

The hairy Leonotis flowers resemble lion’s ears, hence the Latin name leonurus, which mean’s lion’s ear.8  Although the common name used to describe L. leonurus, wild dagga (hemp), suggests some similarity to Cannabis sativa, no relationship exists between the two, either botanically or chemically.18

Identification

Leonotis is an attractive, robust perennial shrub 2-5m tall, with a woody base and pale brown branches.8  Bright orange, tubular flowers are borne in characteristic rounded whorls on the spiky bracts of erect stems.19  The long, narrow and distinctly hairy leaves are opposite with serrate edges.8  

Growing in the summer rainfall area, it flowers profusely in autumn and is a hardy, drought resistant and frost tolerant plant. 

Distribution

It occurs throughout the Southern and Eastern Cape, most of Natal, South-Eastern Gauteng and Mpumalanga.  During autumn, its bright orange flowers are a welcome sight in gardens and on roadsides.       

Chemistry 

Leonotis contains a number of unique diterpenoids, known as furanic labdane type lactones; examples of which include premarrubiin and marrubiin.  However, premarrubiin accounts for only 0.00933 – 0.01567%.14 
   

Premarrubiin            Marrubiin   
        

Tannins, quinones, saponins, alkaloids and triterpene steroids were detected in preliminary screening.  Volatile oils (0.15 – 0.18%) are also present, which probably account for Marloth’s observation that the dried leaves have a peculiar scent and give off a ‘nauseous vapour’ when smoked.18

Pharmacology

Although the pharmacological mechanism of action remains unknown, similar compounds found in Marrubium vulgare are used in European phytomedicine for the treatment of wet coughs and bronchial disease.11  Premarrubiin and marrubiin increase perspiration, the secretion of saliva and gastric juices, and have mild analgesic effects.10  Anticonvulsant activity of an aqueous extract of dried leaf has been demonstrated in vivo in the mouse (dose: 200mg/kg IP).2  Extracts of shade-dried roots of Ethiopian plants were examined for anti-fertility activity in the rat, both in vitro (uterine stimulant activity) and in vivo (anti-implantation effects).  Weak uterine stimulant activity was shown for 95% ethanol extracts but not for aqueous or n-butanol extracts (conc. 2.0%).  Anti-implantation activity was shown by both n-butanol and ethanolic extracts but not by aqueous extracts (dose: 0.93g/kg intragastrically).3  Marrubenol and marrubiin have been implicated in a potent in vitro inhibition of KCl-induced contraction of rat aorta.4 
    
Medicinal Uses 

A number of traditional African medicinal uses of Leonotis have been reported in the literature.6  Amongst the Zulu, cold water infusions of pounded leaves are drawn into the nostrils to relieve feverish headaches.  Mixtures of Leonotis roots with roots or green fruit pulp of Strychnos spinosa Lam. and roots of other plants are prepared in hot water infusions and taken as emetics for snakebite. 

Traditional healers reportedly take a mouthful and bite the patient on the body vigorously enough to draw blood allowing the medicine to enter the circulation.  Infusions of leaves and stems are taken for dysentery or administered orally or as enemas for coughs and colds in humans and animals.  Pounded roots and leaves are added to drinking water to prevent sickness in poultry.  Infusions of leaves, sometimes mixed with leaves of Clutia hirsute E. Mey. Ex-Sond., are and used to treat gall sickness in cattle.  The Xhosa use root bark decoctions to treat snakebite.

Tinctures of the flowers are used for coughs and headaches, while leaves and flowers are used for tapeworm.  The Xhosa also use plant decoctions for the treatment of haemorrhoids, as is the case in the Cape and Mauritius.  In other parts of Africa and Mauritius infusions from flowers, leaves or stems are widely used as purgatives and tonics, as well as in the treatment of influenza, tuberculosis, jaundice, muscular cramps, skin diseases, sores, bee and scorpion stings and snakebite.  Leaves are reportedly smoked for partial paralysis and epilepsy, while decoctions are used to relieve cardiac asthma.  The Nama use decoctions of stems and seeds for headaches and bronchitis.  They also apply ointments, containing powdered leaves, above the eyes for pain. 

In southern Africa teas are reportedly used as diuretics for obesity and haemorrhoids.  Some South African whites regard Leonotis as a folk remedy for diabetes.  However, prolonged use of predominantly dried leaf material reputedly induces impotency, which is resolved by discontinued use. 

Psychotropic Activity

Some consider the shrub’s weak narcotic and sedative effects to be of little therapeutic value.  However, research has focused more on the leaves than the flowers.  Gunn smoked several successive pipefuls of the dried leaves and experienced only ‘unpleasantness’.  Mitchell quotes Marloth, who had taken a dose corresponding to 10g of the dried leaf without effect, as stating that an alcoholic extract of Leonotis leonurus has no toxic or narcotic effects.18  When the leaves are smoked, users frequently comment on the unpleasant taste and the harshness of the smoke on the throat and lungs, side-effects less reported when the flowers are smoked.9, 10  Apparently, the leaves of L. nepetifolia, as well as Leonotis flowers which sprout from a round prickly ball,are more potent and less harsh when smoked.  After a moderate dose of leaf material (3-4g), users report lightheadedness, giddiness, mild euphoria and reduced stress.  Similar effects are achieved with smaller doses of dried flowers.  Higher doses of leaf material (8g or more) may induce mild auditory and/or visual imagery and increased euphoria.9  The best effects are reputedly achieved, ironically so for a herbal product widely touted on the Internet as a hemp substitute, when the flowers are smoked mixed with Cannabis.10  
  
Contraindications 

Use is not recommended for pregnant or lactating women.

Cultivation, Care and Propagation

Growing easily from seeds and cuttings, it does well on the coast and inland.  Good soil, plenty of water, full sun and regular pruning are essential.  Flowers produce a lot of nectar attracting bees and sunbirds.13, 17

References

  1. Abdel-Aziz, A., Brain, K. and A.K. Bashir 1990. Screening of Sudanese plants for molluscicidal activity and identification of leaves of Tacca leontopetaloides (L.) O. Ktze (Taccaceae) as a potential new exploitable resource. Phytotherapy Research 4(2): 62-65.
  2. Bienvenu, E., Amabeoku, G.J., Eagles, P., Scott, G. and E.P. Springfield 2002. Anticonvulsant activity of aqueous extract of Leonotis leonurus (Lamiaceae). Phytomedicine 217(2): 217-223.
  3. Desta, B. 1994. Ethiopian traditional herbal drugs. Part III: anti-fertility activity of 70 medicinal plants. Journal of Ethnopharmacology 44(3): 199-209.
  4. El Bardar, S., Morel, N., Wibo, M., Fabre, N., Llabres, G., Lyoussi, B. and J. Quentin-Leclerq 2003. The Vasorelaxant Activity of Marrubenol and Marrubiin from Marrubium vulgare. Planta Med. 69:75-77.
  5. Ivarsson, M. (1985). Leonotis, in Flora of Southern Africa 28(4): 31-37. Botanical Research Institute, Pretoria.
  6. Hutchings, A. et al. 1996. Zulu Medicinal Plants: An Inventory. Pietermaritzburg: University of Natal Press, pp. 266-67.
  7. Laonigro, G., Lanzetta, R., Parrilli, M., Adolfini, M. and L. Mangoni 1979. The configuration of the diterpene spiroethers from Marrubium vulgare and from Leonotis leonurus. Gazetta Chimica Italia 109 (3/4): 145-150.
  8. Leonotis leonurus: Lion’s ear, Wild Dagga (http://www.spirit-craft.com/Leonotis Leonurus.asp).
  9. Leonotis leonurus (http://en.wikipedia.org/wiki/Leonotis leonurus).
  10. McGaw, L.J., Jager, A.K. and J.V van Staden 2000. Antribacterial, anthelmintic and anti-amoebic activity of South African medicinal plants. Journal of Ethnopharmacology 72(1/2): 247-263.
  11. Pienaar, K. 1994. Gardening with indigenous plants.  Cape Town: Struik.  
  12. Van Wyk, B. et al.  1997. Medicinal Plants of South Africa. [1st Edition] Pretoria: Briza Press.
  13. Van Wyk, B. and Gericke, N. 2000. People’s plants. [1st Edition] Pretoria: Briza Press.
  14. Venter, F. and J. 1996. Making the most of indigenous trees. [1st Edition] Pretoria: Briza Publications.
  15. Watt, J.M. & Breyer-Brandwijk, M.G. 1962. The Medicinal and Poisonous Plants of Southern and Eastern Africa. [2nd Edition] London: Livingstone.
Images by Michael Knott
12-Jun-2007
 
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