Glycosides: Classification, Identification, and Toxicity in Poisonous Plants
Dr.Kumari Anjana
Assistant Professor
Deptt. of Veterinary Pharmacology & Toxicology
Bihar Veterinary College, Bihar Animal Sciences
University, Patna
Classification, identification
and chemical constituents of
poisonous plants - II
2. Glycosides
•
Glycosides are ethers containing a
carbohydrate
moiety and a non-carbohydrate moiety (aglycone)
joined with an
ether bond.
•
They are usually bitter substances.
•
Often the aglycone is released by enzymatic
action when the plant tissue is damaged, as by
wilting, freezing, mastication, or trampling.
•
They are classified on the basis of the structure
and/or properties of the aglycone.
Different kind of glycosides
•
Cyanogenic Glycosides
•
Goitrogenic Glycosides
•
Coumarin Glycosides
•
Steriod and Triterpenoid Glycosides
Cardiac glycosides
Saponins
•
Nitropropanol Glycosides
•
Vicine
•
Calcinogenic Glycosides
•
Carboxyatractyloside
•
Isoflavones
Cyanogenic Glycosides
•
These yield hydrocyanic (prussic) acid when
hydrolyzed.
•
An example is amygdalin found in the kernels of
almonds, apricots, peaches, apples, and the leaves
of choke-cherries.
•
It is hydrolyzed by β-glycosidase to release
hydrogen cyanide, glucose, and benzaldehyde.
•
The hydrogen cyanide is a potent inhibitor of
cytochrome oxidase, a respiratory enzyme.
Goitrogenic Glycosides
•
Goitrogens decrease production for the thyroid hormones by
inhibiting their synthesis by the thyroid gland. As a result, the
thyroid enlarges to compensate for reduced thyroxine.
•
These compounds, called glucosinolates (formerly called
thioglucosides) are commonly found in
Brassica spp.
such as
cabbage,
kale, and rape.
•
They are hydrolyzed by glucosinolates to β-D-glucose, HSO
4
-
, and
derivatives of the aglycone. These include isothiocyanates, nitriles,
and thiocyanates. The glucosinolates are anions, usually found as
potassium salts.
•
The glucosinolase is released from plant tissue by crushing
(mastication) and is also produced by rumen microorganisms.
•
Isothiocyanates may form ring structures and as goitrin (5-vinyl-2-
oxazolidine-thione).
Coumarin Glycosides
•
Coumarin is found in
sweet clover
(Melilotus spp.) as melilotoside.
•
Coumarin is converted by mold growth to
dicoumarol, an
antagonist of vitamin K.
•
Sweet clover poisoning, caused by feeding
mouldy sweet clover hay, is therefore an
induced vitamin K deficiency.
Steriod and Triterpenoid Glycosides
Cardiac glycosides
•
The best known cardiac glycoside is digitoxin,
contained in foxgloves (Digitalis spp.) as the name
suggests, these glycosides contain a sterol group in
their structure.
•
Physiologically, they are potent stimulators of heart
rate and are used medicinally.
•
Milk weeds (Asclepias spp.)
contain cardiac glycosides
(cardenolides) and are extremely toxic to livestock.
•
As little as 100g of milkweed can kill a sheep.
Saponins
•
Saponins are glycosides which have
profuse foaming properties
,
producing a distinctive
honeycombed stable foam
when a aqueous
solution is shaken.
•
They are widely distributed in plants and, in animal nutrition, are
particularly important in temperate
legume forages.
•
They are bitter compounds, affecting palatability and feed intake.
•
They have
growth-depressing properties in poultry and swine
, and
have been implicated in
boat in ruminants
.
•
Saponins contain a polycyclic aglycone (steroid or triterperoid) and
a side chain of sugars attached by an ether bond to C
3.
Nitropropanol Glycosides
•
Many Astragalus species, such as
timber milk vetch
(
Astragalus miser
), owe their toxicity to this class of
glycoside.
•
They are metabolized to--
3-nitro-1-propanol (3NPOH) in ruminants,
and 3-nitropropionic acid in non-ruminants.
•
These compounds, especially 3NPOH, are acutely
toxic, producing
methemoglobinemia.
They also
produce chronic toxicity symptoms, involving
permanent nerve damage.
•
This class of glycosides is also found in crown vetch
(Coronilla spp.)
Vicine
•
Vicine is a glycoside in fava beans (
Vicia
faba
).
•
It cause
haemolytic anemia
(favism) in
people who have a genetic deficiency of
glucose-6-phosphate dehydrogenase
activity in their red blood cells.
•
Fava beans are being utilized, especially in
Canada, as a protein supplement for
livestock.
Calcinogenic Glycosides
•
Some plants, such as
Cestrum diurnum, Solanum,
Solanum malacoxylon, and Trisetum flavescens
, have
glycosides that contain the active metabolite of vitamin
D (1,25-dihydroxycholecalciferol).
•
The consumption of these plants by cattle and horses
results in
excessive levels of active vitamin D
in their
tissues, overriding the feedback control mechanisms
involved in calcium homeostasis.
•
This results in excessive calcium absorption and the
calcification of soft tissues such as arteries and kidney.
Carboxyatractyloside
•
A glycoside called carboxyatractyloside
has been identified as the toxicant in
cocklebur (
Xanthium strumarium
).
•
It produces hepatic lesions, convulsions,
and
severe hypoglycaemia.
Isoflavones
•
These compounds, which are called
phytoestrogens, contain a flavones nucleus
.
•
Examples of isoflavones are genistein, and
coumestrol.
•
Isoflavones are particularly important in
subterranean clover and have caused
extensive
reproductive problems in sheep in Australia.
3.
Proteins
•
Several important inhibitors in plants are
proteins.
•
Of interest is that in some cases the effect
of these is to inhibit the utilization of other
proteins by animals.
Protease (Trypsin) and Amylase Inibitors
•
Soybeans, most other legume seeds, and some grains
(e.g., rye and triticale) contain
trypsin inhibitors.
•
These are small protein molecules which combine with
and
inactivate the digestive enzyme trypsin
in the small
intestine.
•
They cause reduced growth and pancreatic hypertrophy.
•
Amylase inhibitors occur in beans and have been
commercialized as “
starch blockers”
to
reduce obesity
in humans.
Lactins (Hemagglutinins)
•
These are glycoproteins of 60,000-
100,000 MW that cause
agglutination
(clumping) of red blood cells
in vitro.
•
They are found in most types of beans,
including
soybeans.
•
They cause reduced growth, diarrhea,
and interfere with nutrient absorption.
Enzymes
•
An example of an enzyme toxin is
thiaminase,
found in
bracken fern
(Pteridium aquilinum) and
certain
fish such as carp.
•
The enzyme cleaves the
B vitamin thiamine
,
thereby inactivating it.
•
Consumption of bracken fern causes
thiamine
deficiency in some animals.
•
Use of carp and other types of thiaminese-
containing fish in mink diets has produced
thiamine deficiency (Chastek’s paralysis).
Plant Cytoplasmic proteins
•
Many leguminous forages such as
alfalfa
and numerous clovers may cause
boat in
ruminants.
•
This is primarily due to formation of a
stable foam in the rumen
, involving
cytoplasmic proteins in the plant cell
contents.
4. Amino Acids and Amino Acid
Derivatives
Amino Acids
•
There are over 300 amino acids in plants. Not surprisingly,
some of these are toxic. The best known is mimosine,
which is structurally similar to tyrosine.
•
Mimosine
occurs in the tropical forage
L. leucocephala
,
which produces protein-rich leaves that have considerable
potential as livestock feed.
•
Mimosine causes reduced growth and alopecia (loss of
hair) in non-ruminants and is metabolized in the rumen to a
goitrogenic compound, producing
goiter in ruminants.
•
Tryptophan
is a dietary essential amino acid.
•
It can also be regarded as a toxicant because under some
conditions it is metabolized in cattle to
3-methylindole, a
compound responsible for acute bovine pulmonary emphysema
.
•
Dihydroxyphenylalanine (dopa)
occurs in fava beans and has
pharmacological effects.
•
Selenoamino acids,
such as selenocystine,
methylselenocysteine, selenocystethionine, and
selenomethionine, which contain selenium in place of sulphur,
are implicated in selenium toxicity due to consumption of
selenium accumulator plants such as Astragalus spp.
•
There are several
lathyrogenic amino acids
, including
β-cyano-L-alkanine in Vicia spp.
and
β-amino propionitrile in Lathyrus spp.
•
Lathyrus seeds are consumed as food in India, causing a major
public health problem, as
permanent paralysis and skeletal
deformity may occur.
•
In livestock, consumption of
Lathyrus odoratus
seeds by cattle
and horses causes
paralysis, aortic aneurysm, and skeletal
deformity.
•
Lathyrism is the term used to describe the symptoms; both
neurolathyrism (paralysis) and osteolathyrism (skeletal
deformity) are observed.
•
Another toxic amino acid is
1-amino-D-proline.
It is produced
from linatine, found in linseed meal.
1-Amino-D-proline is an
antagonist of pyridoxine (vitamin B
6
).
•
Indospecine is a toxic amino acid found in
Indigofera spicata,
a potentially useful tropical
pasture legume.
•
It is an antagonist of arginine, resulting in
depressed incorporation of arginine into liver-
synthesized proteins.
•
The
brassica anemia factor,
S-methylcysteine
sulfoxide,
is an amino acid derivative. It leads to
red blood cell hemolysis and anemia. It is found in
forage brassicas such as
kale and turnips.
Polypeptides
•
Amanita mushrooms
are extremely poisonous and
owe their toxicity to
cyclic polypeptides.
•
An unusual livestock poisoning problem in Australia
is caused by the larvae of the sawfly, which contain
an octapeptide called lophyrotomin.
•
The sawfly larvae congregate in mounds beneath
the silver-leaf ironbark tree (eucalyptus
melanophloia) and are avidly consumed by cattle.
•
Affected animals show incoordination, trembling,
and liver damage.
Glycosides, ethers with a carbohydrate and non-carbohydrate moiety, are key toxicants in poisonous plants. Cyanogenic glycosides yield hydrocyanic acid, goitrogenic glycosides inhibit thyroid hormone production, while coumarin glycosides can lead to vitamin K deficiency. Steroid and triterpenoid glycosides, such as cardiac glycosides found in foxgloves, impact heart function. Each type has distinct chemical actions, making awareness crucial for veterinary professionals.
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Classification, identification and chemical constituents of poisonous plants - II Dr.Kumari Anjana Assistant Professor Deptt. of Veterinary Pharmacology & Toxicology Bihar Veterinary College, Bihar Animal Sciences University, Patna
2. Glycosides Glycosides are ethers containing a carbohydrate moiety and a non-carbohydrate moiety (aglycone) joined with an ether bond. They are usually bitter substances. Often the aglycone is released by enzymatic action when the plant tissue is damaged, as by wilting, freezing, mastication, or trampling. They are classified on the basis of the structure and/or properties of the aglycone.
Different kind of glycosides Cyanogenic Glycosides Goitrogenic Glycosides Coumarin Glycosides Steriod and Triterpenoid Glycosides Cardiac glycosides Saponins Nitropropanol Glycosides Vicine Calcinogenic Glycosides Carboxyatractyloside Isoflavones
Cyanogenic Glycosides These yield hydrocyanic (prussic) acid when hydrolyzed. An example is amygdalin found in the kernels of almonds, apricots, peaches, apples, and the leaves of choke-cherries. It is hydrolyzed by -glycosidase to release hydrogen cyanide, glucose, and benzaldehyde. The hydrogen cyanide is a potent inhibitor of cytochrome oxidase, a respiratory enzyme.
Goitrogenic Glycosides Goitrogens decrease production for the thyroid hormones by inhibiting their synthesis by the thyroid gland. As a result, the thyroid enlarges to compensate for reduced thyroxine. These thioglucosides) are commonly found in Brassica spp. such as cabbage, kale, and rape. compounds, called glucosinolates (formerly called They are hydrolyzed by glucosinolates to -D-glucose, HSO4-, and derivatives of the aglycone. These include isothiocyanates, nitriles, and thiocyanates. The glucosinolates are anions, usually found as potassium salts. The glucosinolase is released from plant tissue by crushing (mastication) and is also produced by rumen microorganisms. Isothiocyanates may form ring structures and as goitrin (5-vinyl-2- oxazolidine-thione).
Coumarin Glycosides Coumarin (Melilotus spp.) as melilotoside. is found in sweet clover Coumarin is converted by mold growth to dicoumarol, an antagonist of vitamin K. Sweet clover poisoning, caused by feeding mouldy sweet clover hay, is therefore an induced vitamin K deficiency.
Steriod and Triterpenoid Glycosides Cardiac glycosides The best known cardiac glycoside is digitoxin, contained in foxgloves (Digitalis spp.) as the name suggests, these glycosides contain a sterol group in their structure. Physiologically, they are potent stimulators of heart rate and are used medicinally. Milk weeds (Asclepias spp.) contain cardiac glycosides (cardenolides) and are extremely toxic to livestock. As little as 100g of milkweed can kill a sheep.
Saponins Saponins are glycosides which have profuse foaming properties, producing a distinctive honeycombed stable foam when a aqueous solution is shaken. They are widely distributed in plants and, in animal nutrition, are particularly important in temperate legume forages. They are bitter compounds, affecting palatability and feed intake. They have growth-depressing properties in poultry and swine, and have been implicated in boat in ruminants. Saponins contain a polycyclic aglycone (steroid or triterperoid) and a side chain of sugars attached by an ether bond to C3.
Nitropropanol Glycosides Many Astragalus species, such as timber milk vetch (Astragalus miser), owe their toxicity to this class of glycoside. They are metabolized to-- 3-nitro-1-propanol (3NPOH) in ruminants, and 3-nitropropionic acid in non-ruminants. These compounds, especially 3NPOH, are acutely toxic, producing methemoglobinemia. They also produce chronic toxicity permanent nerve damage. symptoms, involving This class of glycosides is also found in crown vetch (Coronilla spp.)
Vicine Vicine is a glycoside in fava beans (Vicia faba). It cause haemolytic anemia (favism) in people who have a genetic deficiency of glucose-6-phosphate dehydrogenase activity in their red blood cells. Fava beans are being utilized, especially in Canada, as a protein supplement for livestock.
Calcinogenic Glycosides Some plants, such as Cestrum diurnum, Solanum, Solanum malacoxylon, and Trisetum flavescens, have glycosides that contain the active metabolite of vitamin D (1,25-dihydroxycholecalciferol). The consumption of these plants by cattle and horses results in excessive levels of active vitamin D in their tissues, overriding the feedback control mechanisms involved in calcium homeostasis. This results in excessive calcium absorption and the calcification of soft tissues such as arteries and kidney.
Carboxyatractyloside A glycoside called carboxyatractyloside has been identified as the toxicant in cocklebur (Xanthium strumarium). It produces hepatic lesions, convulsions, and severe hypoglycaemia.
Isoflavones These phytoestrogens, contain a flavones nucleus. compounds, which are called Examples of isoflavones are genistein, and coumestrol. Isoflavones subterranean clover and have caused extensive reproductive problems in sheep in Australia. are particularly important in
3. Proteins Several important inhibitors in plants are proteins. Of interest is that in some cases the effect of these is to inhibit the utilization of other proteins by animals.
Protease (Trypsin) and Amylase Inibitors Soybeans, most other legume seeds, and some grains (e.g., rye and triticale) contain trypsin inhibitors. These are small protein molecules which combine with and inactivate the digestive enzyme trypsin in the small intestine. They cause reduced growth and pancreatic hypertrophy. Amylase inhibitors occur in beans and have been commercialized as starch blockers to reduce obesity in humans.
Lactins (Hemagglutinins) These are glycoproteins of 60,000- 100,000 MW that cause agglutination (clumping) of red blood cells in vitro. They are found in most types of beans, including soybeans. They cause reduced growth, diarrhea, and interfere with nutrient absorption.
Enzymes An example of an enzyme toxin is thiaminase, found in bracken fern (Pteridium aquilinum) and certain fish such as carp. The enzyme cleaves the B vitamin thiamine, thereby inactivating it. Consumption of bracken fern causes thiamine deficiency in some animals. Use of carp and other types of thiaminese- containing fish in mink diets has produced thiamine deficiency (Chastek s paralysis).
Plant Cytoplasmic proteins Many leguminous forages such as alfalfa and numerous clovers may cause boat in ruminants. This is primarily due to formation of a stable foam in the rumen, involving cytoplasmic proteins in the plant cell contents.
4. Amino Acids and Amino Acid Derivatives Amino Acids There are over 300 amino acids in plants. Not surprisingly, some of these are toxic. The best known is mimosine, which is structurally similar to tyrosine. Mimosine occurs in the tropical forage L. leucocephala, which produces protein-rich leaves that have considerable potential as livestock feed. Mimosine causes reduced growth and alopecia (loss of hair) in non-ruminants and is metabolized in the rumen to a goitrogenic compound, producing goiter in ruminants.
Tryptophan is a dietary essential amino acid. It can also be regarded as a toxicant because under some conditions it is metabolized in cattle to 3-methylindole, a compound responsible for acute bovine pulmonary emphysema. Dihydroxyphenylalanine (dopa) occurs in fava beans and has pharmacological effects. Selenoamino methylselenocysteine, selenomethionine, which contain selenium in place of sulphur, are implicated in selenium toxicity due to consumption of selenium accumulator plants such as Astragalus spp. acids, such selenocystethionine, as selenocystine, and
There are several lathyrogenic amino acids, including -cyano-L-alkanine in Vicia spp. and -amino propionitrile in Lathyrus spp. Lathyrus seeds are consumed as food in India, causing a major public health problem, as permanent paralysis and skeletal deformity may occur. In livestock, consumption of Lathyrus odoratus seeds by cattle and horses causes paralysis, aortic aneurysm, and skeletal deformity. Lathyrism is the term used to describe the symptoms; both neurolathyrism (paralysis) and deformity) are observed. osteolathyrism (skeletal Another toxic amino acid is 1-amino-D-proline. It is produced from linatine, found in linseed meal. 1-Amino-D-proline is an antagonist of pyridoxine (vitamin B6).
Indospecine is a toxic amino acid found in Indigofera spicata, a potentially useful tropical pasture legume. It is an antagonist of arginine, resulting in depressed incorporation of arginine into liver- synthesized proteins. The brassica anemia factor, S-methylcysteine sulfoxide, is an amino acid derivative. It leads to red blood cell hemolysis and anemia. It is found in forage brassicas such as kale and turnips.
Polypeptides Amanita mushrooms are extremely poisonous and owe their toxicity to cyclic polypeptides. An unusual livestock poisoning problem in Australia is caused by the larvae of the sawfly, which contain an octapeptide called lophyrotomin. The sawfly larvae congregate in mounds beneath the silver-leaf ironbark melanophloia) and are avidly consumed by cattle. tree (eucalyptus Affected animals show incoordination, trembling, and liver damage.
