Botany session 9

© Copyright PCNM 2011
Botany and Pharmacognosy
Session 9

Review
Last week we covered
• Phytochemistry, Part II

This Session
During this session we will
cover:
Ethnopharmacology, Part I

Ethnopharmacology
• The World Health Organisation estimates that 65-80% of the world’s
population use traditional medicine as their primary form of health
care.
• In recent years the use of herbal medicine in developed countries
has been increasing.(British Medical Association. Complementary
medicine. New approaches to good practice. Oxford: Oxford
University Press, 1993: 9-36)
• Herbal medicine, in which plants, either dried or in extract form, are
used as therapeutic substances, is one of a number of practices
encompassed by the term “complementary and alternative
medicine” (CAM).

Ethnopharmacology
• Ethnopharmacology is the study of people’s/communities use
(both current and traditional) of plants, fungi, animals,
microorganisms and minerals as medicine.
• When early indigenous people were confronted with illness and
disease they sourced their medicine from the plant and animal
kingdoms. The knowledge that they gathered of these medicinal
substances and toxins was passed on to the next generation and
later on recorded in herbal materia medicas. Many of today’s
medicines date back to use by indigenous people and cultures e.g.
atropine, ephedrine and digoxin.
• The preservation of local knowledge, the promotion of indigenous
medical systems and the conservation of biodiversity have become
a concern for ethnopharmacologists in recent years (Journal of
Ethnopharmacology).

Ethnopharmacology
• Pharmacognosy is the study of
medicines of natural origin. The term
comes from two Greek words:
‘pharmakon’, meaning drug or
medicine, and ‘gnosis’, meaning
knowledge. The American Society of
Pharmacognosy defines
pharmacognosy as “the study of the
physical, chemical, biochemical and
biological properties of drugs, drug
substances or potential drugs or drug
substances of natural origin as well as
the search for new drugs from natural
sources”.

Ethnopharmacology
• Pharmacology is the study of the interaction of biologically active
agents with living systems¹.
• The study of pharmacology is further divided into two main areas:
• Pharmacodynamics looks at the effects of an agent at active sites
in the body i.e. What the drug does to the body².
• Pharmacokinetics is the study of the absorption, distribution,
metabolism and elimination of pharmacologically active agents in
the body i.e. What the body does to the drug².

Ethnopharmacology
• Between 10,000 and 5,000 BC
there is written evidence of the
use of aromatic plants as
medicine in China, India,
Mesopotamia, North and South
America, Egypt and Britain
• The Egyptians used aromatic
plant substances such as resins
as medicine. Isis the Egyptian
goddess of the moon, magic and
sorcery, has the plant resin myrrh
dedicated to her
• Myrrh was used for its anti-
inflammatory actions with a
specific use for inflammation of
the mucous membranes.
• Myrrh comes from the tree
Commiphora molmol native to
Yemen and Somalia
• Frankincense, the resin from
Boswellia is also found in these
regions. It has a long history of
use to treat digestive illnesses,
and for healthy skin, and to treat
arthritis. Boswellia is used now to
relieve arthritis

Ethnopharmacology
• The Tibetan herbal contains
hundreds of plants that are
traditional medicines still used
today .
• LONG PEPPER Piper longum -
Long pepper has demonstrated
hyper-cholesterolaemic and
coronary vasodilating actions. The
berries are the parts used. They
are warming with sweet overtones
and enhance the bioavailability of
other herbs if taken at the same
time
• SAFFRON Crocus sativa -
Saffron has antidepressant effects
and is able to increase oxygen
diffusion in plasma, and reduce
cholesterol and triglyceride levels.

Ethnopharmacology
• RHODIOLA; Rhodiola rosea,
rose root. This large shrub/small
tree comes from the magnolia
family. Its common name comes
from the rose-like perfume when
the roots are cut
• It is a very effective adaptogen to
protect against stress, whether
physical or mental
• It helps the Tibetans cope with the
cold weather and harsh physical
stresses of their environment
Rhodiola rosea,
above, and the
dried root, right

Ethnopharmacology
• Rhodiola rosea is also the name
of a succulent-like plant which
grows at high altitudes
• It is a member of the Crassula
family, and its common name is
golden root.
• Mixtures of the different
rhodiolas are commonly used as
adaptogens

Medicinal foods from the Bolivian-Andes.
• Several species collected are
cultivated food plants, in particular they
are grown for their fruits
• Opuntia ficus-indica (prickly pear)
• Prunus persica (peach)
• Passiflora mollissima (banana
passionfruit)
• Lupinus mutabilis (lupin) is a native
crop of the Central Andes
cultivated as a pulse.
• Ruta graveolens (rue) is also
cultivated and its leaves used as a
condiment in spite of its bad odour
• Some of the food plants are also used
to feed animals;
• Medicago sativa (lucerne), prickly
pear and some wild cacti.
Clockwise from above: prickly pear,
lupin, banana passion fruit, rue
Ethnopharmacology

Branches leaves and spines of
Berberis commutata, the Peruvian
berry, are used medicinally, whilst the
fruit are eaten and used for food
colouring
Prosopis; the fruits are eaten
and made into a beverage,
the whole of the plant is used
medicinally
Ethnopharmacology

• Melilotus (yellow sweet clover) and Erodium (stork’s bill geranium)
are food medicines. Their leaves are eaten raw as a salad, dressed
with oil, to treat kidney disorders
The leaves of Medicago sativa (lucerne) are eaten raw in a salad to
treat gastritis.
• In these cases it is not possible to separate the food use of the plant
from its medicinal action.
Ethnopharmacology
Left: Yellow sweet
clover
Right: Stork’s bill
geranium

• Aromatic plants used as condiments make up an
interesting group
• They are not necessarily being used for their
medicinal value but their presence in the often
rich and heavy meals are more than just culinary,
because they increase the digestibility of these
meals
• They are also used as carminatives to relieve
pain and swelling of the abdomen, to relieve liver
problems, to stop vomiting and to relieve hepatic
colic
• There are five commonly used aromatic plants
from the Lamiaceae family: Hedeoma
mandoniana, Mintostachys andina, Salvia henkei,
Salvia orbignaei and Satureja boliviana
Ethnopharmacology
Satureia boliviana

• The same species of plants are found in different areas of South
America
• Different areas report different usages of the same plants, and of
plants not used in Apillapampa
• Nearly all these plants are weeds that have been introduced into
Bolivia, mainly from Italy and Catalonia (Spain), and grow in the
agricultural fields
• Examples: The use of Chenopodium ambrosioides as a condiment
in South America and its use as the base for a home made liquor in
its native Catalonia. In Italy and Patagonia the leaves and aerial
parts of Stellaria media are used in soups
• These plants significantly increase the medicinal inventory for
South America as well as providing extra nutrients
• Wild food/medicinal species account for 58% of plants used.
Ethnopharmacology

• Many Australian bush medicine
plants have been shown to contain
biologically active compounds
• Bush medicines were more
commonly applied topically than
given orally
• Alstonia constricta, bitter bark, is
used to prepare tonics. It contains
reserpine, a tranquilliser and
antihypertensive
• Some plants used on sores and
wounds contain proteolytic
enzymes that aid healing
• The emu bush, Eremophila
longifolia, and Hakea macrocarpa
were used to heal sores and
wounds
Hakea macrocarpa
Left: Alstonia constricta;
Above: Eremophila longifolia
Ethnopharmacology

• Spilanthes, a native daisy used to treat
toothache contains spilanthol, a local
anaesthetic
• Spilanthes is one Australian native
plant that is used worldwide in
commercial preparations
• Over half the world’s supply of the
drugs hyoscine and scopolamine
come from the Duboisia tree. These
are used to treat seasickness. The
Aborigines use it as an emu and fish
poison but also chew it to relieve
exhaustion and help them cope with
the harsh desert conditions. It is
known as pituri
Spilanthes
Duboisia
Ethnopharmacology

The Campoo inhabitants in Spain use the following plants for health purposes:
• Watercress (Rorippa nasturtium-aquaticum) – used as a blood purifier
• Rice, apples and service tree fruits – used for their astringent and
antidiarrhoeal action
• Carrots enhance vision, walnuts are thought to improve memory; parsley is
believed to increase bone density
Ethnopharmacology

• Celery is eaten to eliminate intestinal
parasites in children
• Beer is consumed by breast-feeding
mothers to improve milk secretion
Some cultivated food plants are also used as
home remedies:
• Onions are heated and used topically on
boils
• Garlic is rubbed onto the anus to help expel
worms
• Fig tree latex is used topically to treat warts
Ethnopharmacology

Some food plants and wild species are prepared as beverage which are
drunk for medicinal purposes only:
• Cinnamon infusion is considered an effective laxative
• Maize stigma decoction (plant is boiled to extract desired constituents) is
drunk as a diuretic
• Elderberry flower decoction is used to treat colds and headaches
• Elderberry inner bark decoction is used to treat rheumatism, gout and as a
vulnerary to heal wounds and burns
Ethnopharmacology

• Many of our ancestral practices have been abandoned and it is
very easy to focus on manufactured products. Even in poor
communities there is greater emphasis on industrially
manufactured drugs
• Knowledge of edible plants with medicinal functions has been
largely lost
• Pharmaceutical industry actively researches plants for any
medicinal qualities but with an eye to isolating individual
constituents for drug manufacture rather than to promote the use
of a food plant
• Ethnopharmacologists study how a natural product is used by a
culture/s as medicine. Through their research the traditional
knowledge of phytotherapy is preserved.
Ethnopharmacology

Checkpoint!

Phytopharmacology
• Herbal pharmacology is founded on the knowledge of
phytochemistry. As a result each phytochemical group will be
discussed in terms of pharmacodynamics and pharmacokinetics.
Key herbs will be discussed individually covering their unique
interactions as well as ethnopharmacology.

Phytopharmacology
• The main constituent groups
• Simple Phenols and Glycosides
• Glucosinolates
• Mucilages
• Essential Oils
• Flavonoids
• Tannins and Oligomeric Procyanidins
• Resins
• Bitters
• Saponins
• Anthraquinones
• Phytooestrogens
• Alkaloids

Simple Phenols
Pharmacodynamics
• From a pharmacological perspective, the
best known simple phenol is salicylic acid. It
is found in willow (Salix species) and poplar
barks (Populus species) and salicylic acid is
subsequently formed on ingestion.
• Salicylic acid has recognized antipyretic and
anti-inflammatory properties which underlie
the use of willow bark for arthritis.
• Aspirin is a synthetic derivative of salicylic
acid which in addition has pronounced
antiplatelet properties due to the presence of
the acetyl group. Salicylic acid lacks this
property and consequently willow bark in not
a suitable natural substitute for aspirin in
cardiovascular patients.
Betula pubescens
Salix alba

Simple Phenols
• Simple phenols are also powerful antiseptics. Arbutin is a phenolic
glycoside found in bearberry which confers bacteriostatic properties
on urine.
• Gastrodin is a simple glycoside from the sedative Chinese herb
Gastrodia elata, which is used to facilitate learning and memory.
• Several studies have shown that extracts of many members of the
mint family (Lamiaceae) have considerable antioxidant activity due
to the presence of phenolic acids such as rosmarinic acid. The
highest antioxidant activity was found in Prunella vulgaris, which
had a rosmarinic acid content of about 5%.

Simple Phenols
• Caffeic acid as well as its
derivatives such as rosmarinic
acid and chlorogenic acids were
found to exert antithyroid activity
after oxidation. The activity may
form the basis of the clinical use of
Lycopus species for
hyperthyroidism. Similar oxidation
products of caffeic acid inhibits
protein biosynthesis in vitro and
these compounds probably
account for the antiviral activity of
topical preparations of Melissa
officinalis (lemon balm).
Lycopus europaeus
(Bugleweed)

Simple Phenols and Glycosides
Pharmacokinetics
• The pharmacokinetics of salicin has been the most extensively
researched phenol in terms of pharmacokinetics.
• Salicin derivatives are first converted into salicin in the stomach or
small intestines. The salicin may then be absorbed in the small
intestine but in humans it is mainly carried to the distal ileum or
colon where gut flora convert this glycoside into its aglycone, known
as salicyl alcohol. Before being absorbed into the bloodstream 4% of
salicyl alcohol is excreted through the bowels.
• The salicyl alcohol is absorbed and oxidised in the blood, tissue and
liver giving rise to salicylic acid, the main active form.
• As a result of hepatic biotransformation 65% of salicylic acid is
conjugated and excreted.

• The bioavailable sodium
salicylate (aspirin) and salicin
are very similar. Salicin has the
longer half-life and the rapid
absorption of salicin as salicylic
acid implies that its conversion is
also rapid. Suggesting the distal
ileum and caecum as the site of
conversion rather than the large
intestine (transit time is about 1
hour).

• Aspirin was developed in the 19th century when scientists began to
investigate the antipyretic and anti-inflammatory effects of willow
bark. They isolated salicylic acid, not salicin, from the bark. Although
adopted into mainstream medicine salicylic acid was a strong irritant
to the stomach. This led to the development of aspirin in an attempt
to minimize gastric irritation. Although is was more active than
salicylic acid as an analgesic and antiplatelet, aspirin was still a
gastric irritant.
• Had they used salicin instead the early scientists might have
realized that nature had already designed a derivative of salicylic
acid which converted into a high yield of a bio available salicylic acid
and was also kind to the stomach.

• A number of plant glycosides are modified by the action of gastric
acid or the alkaline conditions of the duodenum.
• Harpagophytum procumbens (devil’s claw) has oral
antiinflammatory activity. However when it is incubated with
gastric acid, harpagogenin is generated from harpagoside and
loses its antiinflammatory activity in oral dose models.
• Although hapagoside is not the final bioavailable form the
research suggests gastric acid is detrimental to the
antiinflammatory activity of devil’s claw. As a result preparations
of this herb should be enterically coated or at least taken
between meals to optimize the bioavailability of the anti-
inflammatory components.

Glucosinolates
Pharmacodynamics
• In traditional herbal medicine strong skin
irritants and inflammatory substances were
empirically used as anti inflammatory agents
on tissues and organs remote from the site
where the irritant was applied.
• The mode of action of glucosinolates as skin
irritants is characterised by an ability to
influence deeper regions of the body by
reflex effects mediated by the nervous
system.
• An example of glucosinolate irritation is the
application of nettle on arthritic joints. This
produces a stinging sensation and
subsequent reduction in pain and
inflammation.

Glucosinolates
• Glucosinolates can be used in the form of ointments, compresses,
liniments or plasters.
• The mustard compress is still used in Europe today for bronchial
infections and detoxification in chronic disease. However mustard oil
is highly corrosive and if applied to the skin for too long will cause
blistering and may even permanently scar the skin.

Glucosinolates
• Recent research on glucosinolates
has focused on their various
transformation products and the
potential prevention of cancer. The
anticarcinogenicity of these
compounds, specifically in relation
to brassica vegetables has been
recently reviewed. Alterations in
phase I and phase II detoxification
enzymes are suggested as
possible mechanisms by which
these plant constituents might
inhibit chemical carcinogenesis.

Mucilages
Pharmacodynamics
• Primarily used as topical emollients
and as demulcents, mucilages are
used in the management of
inflammatory conditions of the
digestive system. The anti-
inflammatory effect is probably
more than just mechanical,
although the protective benefits of
a layer of mucilage on the digestive
mucosa are obvious.
• Mucilages are applied topically for
an anti-inflammatory effect but also
for a drawing and healing effect on
wounds and infected skin lesions.

Mucilages
• The reflex demulcency action of mucilages is not a recognised
pharmacological model however experimental support for this action
does exist.
• An extract of marshmallow root (Althaea officinalis) and the isolated
mucilage demonstrated significant antitussive activity in an animal
test. Doses were administered orally and cough from both
laryngopharyngeal and tracheobronchial stimulation was depressed.
The mucilage was as potent as some non-narcotic antitussive drugs.
The reverse phenomenon has also been observed with acid reflux
into the distal oesophagus can trigger a cough.

Mucilages
• As mucilages are too large to be absorbed into the blood stream the
mechanism of action is mediated by the vagus nerve whereby the
soothing effect of the upper digestive tract causes reflex effects on
the tracheobronchial musculature.
Marshmallow

Mucilages
• Mucilages also function as bulk laxatives and are a class of soluble
fibre.
• Psyllium husks have been well studied in their effective use for
lowering blood cholesterol, however it must be taken with food to be
effective. As the psyllium binds to the cholesterol in food preventing
it from being absorbed into the blood stream and dragging it out
through the stool.
• Psyllium and other soluble fibres help retain glucose in the gut and
therefore reduce blood insulin levels after eating. There is a clear
dose-related response in regards to glucose retention in the gut.
• Soluble fibres and mucilages also act as prebiotics enhancing the
population of beneficial organisms in the gut flora.

Essential Oils
Pharmacodynamics
• Essential oils can be administered either by
inhalation, applied to the skin or orifices, added to
baths or ingested. There is no doubt that ingested
oils or those applied to the skin or added to baths
are absorbed into the bloodstream in significant
quantities. The inhalation of essential oils was
previously considered a placebo but evidence in
now accumulating to support a pharmacological
action.
• Considering the great chemical diversity of
essential oils they exhibit a wide variety of
pharmacological activities. The most common
action amongst essential oils is their antimicrobial
and spasmolytic actions.

Essential Oils
• Of 53 essential oils tested against four organisms, only a few oils
exhibited remarkable activity, particularly thyme and origanum which
contain phenols. Pseudomonas aeruginosa was the least
susceptible organism and Candida albicans the most susceptible.
All 66 isolates of Staphylococcus aureus tested were susceptible to
tea tree oil (Melaleuca alternifolia) at 0.5% concentration, including
antibiotic resistant strains (16).
Melaleuca
alternifolia

Essential Oils
• The antimicrobial activity of essential oils has been found to be due
to a cytotoxic activity most probably exerted by membrane
associated reactions.
• Concentrations of tea tree oil which inhibit or decrease growth of
Escherichia coli have shown to also inhibit glucose-dependent
respiration and stimulate the leakage of intracellular potassium.
• Of five components tested for antibacterial activity , cinnamic
aldehyde was the most active, followed by citral, geraniol, eugenol
and menthol. In another study linalool was the most active
antibacterial agent and citral and geraniol were the most effective
antifungal agents.
• Essential oils with high monoterpene hydrocarbon levels were very
active against bacteria although not against fungi, with exception of
dill.

Essential Oils
• Information about the topical use of
essential oils is important but can
they also achieve an antimicrobial
effect within the body e.g. Juniper
for urinary tract infections.
Essential oil components are
excreted into the urine in
metabolized forms, mainly as
glucuronide conjugates and
sulphates. As a result the
antimicrobial activity may not be
reflected in the urine, further
studies are required.
Juniper

Essential Oils
• The spasmolytic activity of essential oils has been observed many
times on isolated smooth muscle preparations and forms much of
the basis of their use in functional gastrointestinal disorders.
• The effects of essential oils from 22 plants and some of their
constituents on tracheal and ileal smooth muscle was investigated.
All of the oils had relaxant effects on tracheal smooth muscle, the
most potent being angelica root, clove and elcampane root. Sixteen
oils inhibited the phasic contractions of the ileal muscle preparation,
the most potent being elecampane root, clove, thyme and lemon
balm (17).

Essential Oils
• Carminative relax sphincters and
assist in the expulsion of
intestinal gas. Their activity is
related to spasmolytic activity.
Certain essential oils or essential
oil containing herbs have been
traditionally used as carminatives
over many years.
Peppermint

Essential Oils
• Thyme inhibited agents which
stimulate smooth muscle and also
demonstrate a spasmolytic effect
on various isolated smooth
muscles. The relaxing effect of
bradykinin was also potentiated.

Essential Oils
• The effects of peppermint oil on the gastrointestinal smooth muscles
resemble those of calcium antagonist drugs. Peppermint oil
markedly attenuated contractile responses of the smooth muscle of
the colon to acetylcholine, histamine, serotonin and substance P. It
also reduced contractions evoked by potassium depolarization and
inhibited potential dependent calcium currents in rabbit jejunum
smooth muscle cells in a dose-dependent manner (18).

Essential Oils
• The sedative activity of essential oils such as lavender is commonly
recognized and support by studies. Examples include lavender,
lemon balm and clove
• Stimulant activity has been attributed to some essentials oils.
Examples rosemary.

Flavonoids
Pharmacodynamics
• Most studies conducted on flavonoids have
used in vitro models, often isolated enzyme
systems. The findings of these studies need to
be interpreted with caution since it is uncertain
that oral doses of flavonoid glycosides or even
their aglycones can reach sufficient
concentrations in living organisms to reproduce
these effects.
• The original pharmacological interest in
flavonoids arose during vitamin C research in
the 1930s. Studies by Hungarian workers
indicated that a number of vegetables and
fruits (notably citrus) contained substances
capable of correcting certain abnormalities
associated with scurvy.

Flavonoids
• Research did confirm the
therapeutic value of flavonoids
for fragile capillaries.
• Decreased capillary fragility
means improved connective
tissue tone and a reduced
tendency for capillary contents
to leak into surrounding tissue.
This implies that flavonoids will
prevent oedema associated
with inflammation and stasis.
Such effects from flavonoids
are the only benefits which are
reasonably well established
from clinical trials.

Flavonoids
• The in vitro antioxidant properties of flavonoids have been the focus
of much research in recent years. The ability of flavonoids to
complex prooxidant metallic ions such as iron probably augments
their antioxidant effects in specific circumstances. Of particular
interest is the ability of flavonoids to inhibit macrophage-mediated
oxidation of low density lipoprotein .
• The antioxidant properties of flavonoids could also contribute to
observed antiinflammatory and antiplatelet effects and are related
not only to their structural characteristics but also to their ability to
interact with and penetrate the lipid bilayers of the cell membrane.

Flavonoids
• The following enzyme activities are inhibited to varying degrees by
flavonoids in vitro: cyclooxygenase, lipoxygenase, lens aldose
reductase, xanthine oxidase, cyclic GMP, phosphodiesterase, cyclic
AMP phosphodiesterase, angiotensin-converting enzyme,
aromatase and thyroid peroxidase.
• More research is needed to determine which of these activities can
realistically translate into clinical effects. Since enzyme-inhibiting
activity depends on the structure of the flavonoid some compounds
are more likely to be clinically effective than others.

Flavonoids
• Flavonoids exhibit preventative activity
against chemical carcinogens and tumour
promotion in animal models.
• Anxiolytic properties have been
demonstrated for flavonoids chrysin and
apigenin which selectively bind with high
affinity to the central benzodiazepine
receptor.
• The relationship between dietary
flavonoid intake and cardiovascular
disease demonstrated flavonoid intake
was significantly inversely associated with
mortality and incidence of stroke(4).
Hawthorn berries

Flavonoids
Pharmacokinetics
• Flavonoid glycosides are a common component of many plants and
are a significant class of archetypal plant constituents with
pharmacological activity. Flavonoids often have poor bioavailability
because they are largely decomposed by bowel flora.
• Studies have shown that flavonoid-O-glycosides are converted into
the aglycone by bowel flora. But the decomposition can extend
further than this, as the aglycone undergo further breakdown by a
process known as C-ring fission to give two different phenolic
products.

Flavonoids
• Studies have shown:
• Oral doses of flavonoid aglycones are less bioavailable (as the
flavonoid) than their glycosides because they are more
susceptible to ring fusion.
• Levels of a flavonoid aglycone in the bloodstream will vary
according to:
• Whether it is administered as an aglycone or glycoside
• If given as a glycoside the form of the glycosidic prodrug
• The nature of the individual bowel flora which is partly
dependent on the individual diet
• Generally only about 20% or less of the administered glycoside
will be absorbed as the intact aglycone.
• Flavonoid C-glycosides may exhibit similar mechanisms.

Flavonoids
• The issue of bioavailability of the
flavonoid aglycone quercetin
illustrates the issues. The rational
for including quercetin in many
nutritional products is generally
based on in vitro research or in vivo
models following dosage by
injection. However studies have
concluded that the bioavailability of
quercetin is poor.
• This is due to its propensity to
rapidly undergo C-ring fission.

Flavonoids
• The Zutphen Elderly Study and the Netherlands Cohort Study
studied the association between mortality from coronary heart
disease and flavonoid intake. The study measured plasma quercetin
concentrations. Following intake of the equivalent of 215g raw
yellow onions a mean peak plasma concentration of 196ng/ml was
reached after 2.9 hours. The elimination half life was slow at about
17 hours, suggesting possible enterohepatic recirculation. This
concentration probably only represents a small proportion , less than
5% of the administered dose(4).

Summary
Today we have covered:
• Ethnopharmacology, Part I

Next Session
We will cover:
• Ethnopharmacology, Part II

Preparation
Brief Notes
• Don’t forget to log on to the LMS and download and print off your
brief notes and handouts for the next session.

Botany session 9

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