Volume 174, 4 November 2015, Pages 520–539
Review
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Abstract
Ethnopharmacological relevance
Leonotis leonurus,
locally commonly known as “wilde dagga” (=wild cannabis), is
traditionally used as a decoction, both topically and orally, in the
treatment of a wide variety of conditions such as haemorrhoids, eczema,
skin rashes, boils, itching, muscular cramps, headache, epilepsy, chest
infections, constipation, spider and snake bites. The dried leaves and
flowers are also smoked to relieve epilepsy. The leaves and flowers are
reported to produce a mild euphoric effect when smoked and have been
said to have a similar, although less potent, psychoactive effect to
cannabis.
Aim of the review
To
amalgamate the botanical aspects, ethnopharmacology, phytochemistry,
biological activity, toxicity and commercial aspects of the scientific
literature available on L. leonurus.
Methods
An extensive review of the literature from 1900 to 2015 was carried out. Electronic databases including Scopus®, SciFinder®, Pubmed®, Google Scholar® and Google® were used as data sources. All abstracts, full-text articles and books written in English were considered.
Results
The phytochemistry of particularly the non-volatile constituents of L. leonurus
has been comprehensively investigated due to interest generated as a
result of the wide variety of biological effects reported for this
plant. More than 50 compounds have been isolated and characterised. L. leonurus
contains mainly terpenoids, particularly labdane diterpenes, the major
diterpene reported is marrubiin. Various other compounds have been
reported by some authors to have been isolated from the plant,
including, in the popular literature only, the mildly psychoactive
alkaloid, leonurine. Leonurine has however, never been reported by any
scientific analysis of the extracts of L. leonurus.
Conclusion
Despite the publication of various papers on L. leonurus,
there is still, however, the need for definitive research and
clarification of other compounds, including alkaloids and essential oils
from L. leonurus, as well as from other plant parts, such as
the roots which are extensively used in traditional medicine. The
traditional use by smoking also requires further investigation as to how
the chemistry and activity are affected by this form of administration.
Research has proven the psychoactive effects of the crude extract of L. leonurus,
but confirmation of the presence of psychoactive compounds, as well as
isolation and characterization, is still required. Deliberate
adulteration of L. leonurus with synthetic cannabinoids has
been reported recently, in an attempt to facilitate the marketing of
these illegal substances, highlighting the necessity for refinement of
appropriate quality control processes to ensure safety and quality. Much
work is therefore still required on the aspect of quality control to
ensure safety, quality and efficacy of the product supplied to patients,
as this plant is widely used in South Africa as a traditional medicine.
Commercially available plant sources provide a viable option for
phytochemical research, particularly with regard to the appropriate
validation of the plant material (taxonomy) in order to identify and
delimit closely related species such as L. leonurus and L. nepetifolia which are very similar in habit.
Graphical abstract
Keywords
- Leonotis leonurus;
- “Wilde dagga”;
- Ethnopharmacology;
- Labdane diterpenes;
- Marrubiin
