SAPONINS
Mills, S. 1991, “The Essential Book of Herbal Medicine”, Penguin
Pengelly, A.1996, “The Constituents of Medicinal Plants: An Introduction to the Chemistry &
Therapeutics of Herbal Medicines”, Sunflower Herbals
Wohlmuth, H.1998, “Pharmacognosy and Medicinal Plant Pharmacology”, Southern Cross
University
 Saponins are water-soluble phytochemicals
which are characterised by having detergent
properties and produce a foam when dissolved in
water – they are soaps (sapo = soap in Italian).
 They are often referred to as triterpene glycosides
or steroidal alkaloids.
 These detergent properties have
been used in the past where saponin
rich plants have been used as soap
substitutes. Such plants are still being used
today, especially in the cleansing of sensitive
fabrics e.g. Saponaria officinalis (soapwort)
 Like
other detergent compounds, saponin
molecules possess a water-loving polar
(hydrophilic) and a water-hating non-polar
(hydrophobic) or fat-loving (lipophilic) end of
the molecule. The polar end makes the molecule
soluble in water while the non-polar end enables
it to dissolve grease and other non-polar
substances.
 The aglycone of a saponin is often referred to as
the sapogenin.
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TYPES
 On the basis of the chemical structure of the
sapogenin, saponins are divided into two groups 
steroidal saponins and triterpenoid saponins
 STEROIDAL SAPONINS
 The sapogenin of steroidal saponins is steroidal
in nature, with the glycone attached to carbon
number 3. These have a close structural
relationship
with
steroid
hormones,
cardioactive glycosides and vitamin D, and this
makes these saponins of commercial interest as
starting points for the synthesis of a number of
drugs.
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 The effect on
 the female reproductive system of fenugreek
containing the sapogenin, diosgenin
 inflammatory conditions of wild yam with
dioscin and sarsaparilla (sarspogenin and
smilogenin)
 the reproductive system of bethroot (trillium)
suggests that the steroidal nature of their
saponins may be interacting with steroidal
receptors in the body as the triterpenoids do, or
even may act as precursors to the steroidal
hormones.
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 The toxic effects of the nightshade family (e.g.
the problems with greening in potatoes), are
due to steroidal saponins with alkaloid
properties.
 Cholesterol is a common precursor to steroidal
saponins in plants
 Steroidal saponins are most common in
monocotyledons but are also found in some
dicotyledons. Some examples of families and
genera containing this type of saponin are:
Monocotyledons
Dicotyledons
Dioscoraceae
Dioscoria
Liliaceae
Trillium, Ruscus,
Yucca
Amaryllidaceae
Agave
Fabaceae
Trigonella
Scrophulariaceae
Digitalis
Apocynaceae
Strophanthus
Wild Yam (Dioscorea villosa):
 Some Dioscorea species contain steroidal
saponins, including dioscin, which yields the
sapogenin diosgenin. This aglycone was the raw
material used in early semi-synthetic
production of steroidal hormones and other
steroidal compounds of pharmaceutical
interest. Diosgenin is still used in hormone
production.
 Galenical preparations of Dioscorea are used as
spasmolytics and anti-inflammatories,
particularly in the GIT and the female
reproductive tract.
 It is also a visceral relaxant and
a mild peripheral vasodilator.
 Dioscorea is used in rheumatic
inflammatory conditions
(including rheumatoid arthritis),
colitis, cramps, dysmenorrhoea and ovarian and
uterine pain.
Sarsaparilla (Smilax officinalis):
 Contains 1 – 3% steroidal saponins, including
sarsaponin and smilasaponin, based on the two very
similar aglycones sarsasapogenin and smilagenin.
Saponins may bind bacterial endotoxins in the
intestines, preventing their absorption into the
bloodstream.
 The German Commission E states that taking
Sarsaparilla preparations lead to gastric irritations
and temporary impairment of the kidneys.
 Smilax does not contain testosterone
and there is no evidence of any
anabolic action.
Fenugreek (Trigonella foenum-graecum):
 Contains saponins which yield about 1.5%
diosgenin and other sapogenins when
hydrolysed.
 The content of steroidal saponins may be
reflected in actions such as anti-inflammatory,
galactagogue and hypoglycaemic.
 Saponin rich extracts have been
shown to be anti-diabetic and to
reduce blood cholesterol levels.
Butcher’s broom (Ruscus aculeatus):
 Contains about 10% of steroidal saponins, known
as ruscogenin and neo-ruscogenin. Ruscogenin is
the aglycone of ruscin.
 Ruscus tones the venous system and reduces
capillary fragility. Clinical trials have shown
ruscogenins to be vasoconstricting and antiinflammatory.
 Triterpenoid saponins:
 Most of these saponins contain at least one
carboxylic (-COOH) group.
 The
common saponin actions described
earlier are also evident in this group, that is,
anti inflammatory and reflex actions.
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 Triterpenoid saponins are mostly found in
dicotyledons:
Dicotyledons
Fabaceae
Glycyrrhiza
Asteraceae
Solidago
Apiaceae
Bupleurum
Primulaceae
Primula
Phytolaccaceae
Phytolacca
Polygalaceae
Polygala
Caryophyllaceae
Stellaria
Licorice (Glycyrrhiza glabra):
 Glycyrrhiza contains over a dozen different
triterpenoid saponins, the main one being
glycyrrhizic acid at 2 – 6%, which occurs in the
plant as a mixture of potassium and calcium
salts. This mixture is known as glycyyrhizin,
an intensely sweet compound, 50 times
sweeter than sucrose.
 The saponin of glycyrrhizic acid
is glycyrrhetinic acid.
(figure 6.53, page 95)
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 The saponins of licorice have anti-inflammatory,
demulcent, expectorant and antiviral (herpes
virus) properties and also affect hormone levels
and hormone like actions
 Mineral corticoid action (mimics aldosterone):
increases Na+ and Cl- while decreasing K+, thus
leading
to
fluid
retention
(and
contraindications of oedema and hypertension
 Mimics ACTH stimulating glucocorticoid
secretion from the adrenal cortex
 Inhibits the breakdown of
glucocorticoid hormones
(including cortisol), aldosterone
and progesterone
 Clinical studies have shown that glycyyrhizic
acid and glycyrrhetinic acid accelerate the
healing time of gastric ulcers, apparently due
to increased rate of mucous secretion.
 Licorice contains a variety of potentially
active constituents apart from saponins ,
including isoflavones and other flavonoids.
 Oat seedling roots observed by fluorescence
microscopy, showing the natural fluorescence of
the saponin, avenacin. The left-hand image
shows the tip of a main root axis; the right-hand
image shows a root lateral emerging from a root
axis.
Properties of saponins
 Haemolysis, therefore, saponins are not for
long term or high dose use. On injection, like
all detergents, they cause lysis of the blood
cells and are thus highly toxic. However,
o Because saponins are hydrolysed in the GIT
before any absorption takes place and the
free sapogenins do not display haemolytic
properties, there is little to no haemolytic
risk associated with oral ingestion (with
the possible exception of bleeding ulcer).
o The haemolytic potential varies amongst
saponins  those found in Panax ginseng
are practically devoid of haemolytic activity
while the saponins of Phytolacca spp. are
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potent haemolytic agents.

Upper GIT irritation, and therefore, act as a
reflex expectorant. This effect can be best
described as a slight irritation of the mucous
membrane. The action conveys two general
actions of saponins:
o Increased absorption, following increased
blood supply to the mucosa
o
Reflex expectorant action, mediated by the
embryonic neural link between the mucous
membranes of the GIT and the respiratory
tract.
Important
expectorant
herbs
containing saponins include Polygala senega,
Verbascum thapsus, Viola odorata
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o
This reflex stimulation of the stomach wall is a
result of the fact that most saponins, when
taken in bulk, have an emetic effect – their
detergent action promotes elimination on the
part of the stomach. When taken in sub-emetic
doses, the emetic action becomes a reflex
stimulating expectoration as with such wellknown alkaloidal emetics as lobelia (Lobelia
inflata)
or
ipecacuanha
(Cephaelis
ipecacuanha).
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 Other saponins have a less irritating effect on
the digestive system, actually settling it and
aiding the absorption of important minerals.
The saponins of spinach, asparagus, beetroot,
oats and many of the legumes are likely to
have a useful action.
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 Facilitation of solubility and absorption of
larger molecules
 Interruption of absorption of transport of
small molecules  gymnema disrupts the
absorption and uptake of sugar
 Anti-inflammatory effects, other than that
conveyed by the local effect in the GIT. Good
examples
of
anti-inflammatory
herbs
containing saponins are Stellaria media,
Aesculus hippocastanum, Solidago virgaurea,
Scrophularia nodosa
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 Cholesterol-lowering
effects
by
inhibiting
absorption and stimulating bile excretion e.g.
Trigonella foenum-graecum and Glycyrrhiza
glabra. However, they need to be consumed in
quite large amounts.
 There is also a group of saponins with prospects for
vascular disorders, including varicose veins,
thrombotic conditions, arteritis, phlebitis and
arteriosclerosis. These are indications for the
vascular remedy Aesculus hippocastanum, but
could also include Achillea millefolium and Tilia
spp.

Anti-microbial effects, especially fungal
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 Anti-viral – topical and gut only
 Hepatoprotective effects –
saikosaponins from Bupleurum spp (Apiaceae),
ginsenosides from Panax ginseng Araliaceae)
 Saponins are highly toxic to fish and other cold blooded
animals, and many cultures all over the world have
exploited saponin containing plants as fish poisons. In
this form they are harmless to humans.
A
number of common foods contain saponins
e.g. tomatoes, asparagus, beetroot, oats and some
legumes