gylcosides presented by bahadur singh hod department of pharm. sciences govt. polytechnic college...
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GYLCOSIDES
Presented by BAHADUR SINGH
HODDepartment of Pharm. Sciences
Govt. Polytechnic college for GirlsPatiala
Glycoside Definition
A substance which on hydrolysis– yields a reducing sugar– + one or more non-sugar substances
(genin/aglycone)• Normally aromatic in nature• Known as the aromatic aglycone or genin
portion
Glycoside = Broad & general term
Embraces all the many various
combinations of sugars & aglycones
e.g. Cardiac glycosides, flavonoid
glycosides, phenolic glycosides etc
important to determine which isomer has the activityα or β glycosidal bond from an α or β pyranose sugar ring
natural glycosides tend to have β-linkageacid hydrolysis to cleave α or β glycosides
identify component part of moleculecheck stereochemistry with β-glucosidase
Classification:• Atom from the aglycone involved in the glycosidic linkage:
• Aglycone- O- Sugar O-glycosides• Aglycone- C- Sugar C-glycosides• Aglycone- S- Sugar S-glycosides• Aglycone- N- Sugar N-glycosides
• Number of sugars:• One sugar monosides e.g. Salicin.• Two sugar Biosides e.g. Diosmin.• Three sugars Triosides e.g. Digoxin.
• Nature of the glycoside:• Primary glycosides: Originally present in the plant e.g. Purpurea A• Secondary glycosides: Resulted from removal of one sugar from the
primary glycosides e.g. Digitoxin
Type of the glycosidic linkage:a- glycosidesb- glycosidesBotanical source:Digitalis glycosidesSenna glycosides.Therapeutic use:Analgesic glycosides.Purgative glycosides.Cardiac glycosides.Chemical nature of the aglycone:Flavone glycosides.Steroidal glycosides.Aldehydic glycosides.MOST COMMONLY USED
Stability of Glycosides:1- Effect of acid hydrolysis:• Acids split sugars from the aglycones.• The acetal linkage is more readily cleaved than the linkage
between the individual sugars of the sugar chain.• C-glycosides are resistant to acid hydrolysis.2- Effect of alkaline hydrolysis:
A- Strong alkalis:• Hydrolysis of ester groups.• Opening of lactone rings e.g. Cardiac glycosides.
B- Mild alkalis:• Hydrolysis of ester groups e.g. Lanatoside A to Purpurea A• Opening of lactone rings e.g. Cardiac glycosides
3- Enzymatic hydrolysis:
Split the sugars stepwise starting from the terminal sugars.All plants producing glycosides have enzyme that can hydrolyze these glycosides.Enzymes are specific for the type of glycosidic linkages:Emulsin can hydrolyze b- glycosidesInvertase can hydrolyze a- glycosidesMyrosin can hydrolyze s-glycosides.
Physical Characters:• Solids either amorphous or crystalline.• Non volatile.• Usually bitter in taste.• Soluble in water and polar organic solvents.• . Reduce Fehling’s solutions only after
hydrolysis
Extraction and Isolation• Because of the wide range of physical and chemical properties of
glycosides and other constituents associated with them, no common general method for their isolation is recommended.
• Water, methanol, water-ethanol and ethanol are the most common solvents for extraction of glycosides.
• Precautions before extraction– Deactivation of enzymes:
• Drying for 15-30 min at 100 degree C followed by slow drying at a low temperature.
• Dipping the fresh material into boiling water or boiling alcohol for 10-20 min.
• Boiling the fresh plant material with acetone.• Carrying out the extraction at very low temp.• Freeze-drying of the plant material before extraction (lyophilization).• Carrying the extraction in the presence of (NH4)2SO4.
Maintenance of neutral conditions:
Neutral pH should be assured before and during extraction because:Acidity may result in hydrolysis. This is overcome by addition of CaCO3. Mild alkalinity may sometimes produce racemization.
Defatting of fat-rich organs (e.g. seeds) before extraction:
High amounts of lipoids hinder glycoside extraction. Defatting is usually carried with petroleum ether
Classification• On the basis of aglycone structure
• [1] Alcoholic and Phenolic Glycosides• [2] Aldehydic Glycosides• [3] Cardio-Active Glycosides• [4] Anthracene (Anthraquinone) Glycosides• [5] Saponins • [6] Cyanophore • [7] Isothiocyante• [8] Flavonoids• [9] Coumarin and Furanocoumarin• [10] Glycosidal bitters and Miscellaneous
Alcoholic and Phenolic Glycosides1- Salicin
Source: Salix species (Willow bark).Nature: Primary achholic and Phenolic glycoside
(monoside).Uses: Analgesic- Antipyretic- Anti-inflammatory.
CH2OH
O-glc
Enzyme
CH2OH
OHSaligenin
(Salicyl alch.)
+Glucose
AcidO
CH2OH
HOH2C
+Glucose
Saliretin
OH
O-glc
OCH3
O-glc
OH
OH
+ GlucoseHydrolysis
Hydroquinone
ArbutinMethylarbutin
2- Arbutin & Methyl ArbutinSource: Uva Ursi (Bearberry leaves).Nature: Primary Phenolic glycoside (monoside).Uses: Diuretic- Bactericidal.
Aldehydic Glycosides1- Glucovanillin
Source: Vanilla pods.Uses: Flavouring agent- Spray reagent.
CHO
O-glc
OCH3
CHO
OH
OCH3
Enzymatic Hydrolysis
Vanillin
Green vanilla podsBitter in taste
Odourless
Brown vanilla podsSweet in tasteVanilla odour
+ Glucose
Glucovanillin
Cardio-Active Glycosides
• A small group of plant glycosides act directly on the heart muscle.
• These include (but are not limited to cardiac glycosides or cardenolides)
• Cardenolides are steroidal glycosides exert a slowing and strengthening effect on the failing cardiac muscle.
Basic Structure of Cardiac Glycoside
Steroids in nature exerts powerful action on the cardiac muscle, as a glycoside the sugar moeity is attached to the #3 position of the steroid nucleus2 types of steroid aglycone
Cardenolide (C23) – C17 β side chain -- , - unsaturated 5 – membered ring
Bufadienolide (C24) – homolog of cardenolide, C17 unsaturated 6 – membered lactone ring
- origin prototype – bufalin (Toad – Bufo sp)
To obtain optimum cardiac activity – aglycone must possess an , unsaturated lactone ring on C17 of the steroid nucleus and A/B and C/D on cis – configuration (same side substituent)
Sugar – confers the molecule's solubility property, its absorption and distribution in the body (O- hydroxyl group – rapid onset of action)
Digitalis purpurea – Purple Foxglove
• Definition: • Digitalis consists of the dried leaves of
Digitalis purpurea. • It is required to contain at least 0.3% of total
cardinolides calculated as digitoxin.
Pharmacological Action of Cardiac Glycosides
• Effectiveness depends on both the aglycones and the sugar attachments.
• Medicinal action depends on the aglycone
• But the sugars make the compound more soluble in increases the fixation of the glycoside to the heart muscle
Digitalis purpurea - Collection
• There is a general belief that the pharmacological activity of the leaves increase during the course of the day to reach a maximum in the early afternoon (when they should be harvested).
• This was supported by assays done in 1956 which showed a greater activity of the leaves at noon than 8am, irrespective of if the leaves where in the sun or shade.
• However, other work indicates that there is no glycosidal content variation of the leaves when measured at 3-hour intervals.
Active Constituents
• glycosides– purpurea glycoside A– purpurea glycoside B
• (2 main actives in the fresh leaf)
– Glucogitaloxin
• At C-3 of the genin: a linear chain of 3 digitoxose sugar moieties terminated by glucose
Digitalis purpurea• Allied Drugs
• D. thaspi• D. lutea• D. ferruginia
• Adulterants
• Verbascum thapsus (mullein leaves)• Symphytum officinalis (Comfrey)• Primula vulgaris (Primrose)• Inula helenium (elecampane)• Urtica dioica (stinging nettle)
Strophanthus kombe
• Part Used: Dried seeds (ripe)
• Habitat: East Africa.
• Greek strophos (a twisted cord or rope) anthos (a flower)
•
Bufadienolides
• Less commonly distributed in nature than cardenolides
• Occur in some Liliaceae and Ranunculaceae Species. Also occur in toad venoms.
• Therapeutically there is not much value as the therapeutic index is low and production of side effects high.
• Squill, however has a time-honoured place as an expectorant
• Widely used in the treatment of cough.
Urginea maritima – (Liliaceae)• Definition: Consists of the
dried sliced bulbs of Urginea maritime, from which the membranous outer scales have been removed. It is commercially known as white squill.
• Description: A perennial herb growing up to 1.5 m from a large white (or red) bulb. It has a single flowering stem, a rosette of large basal leaves, and a dense spike of white flowers.
Cardiac Glycoside
• General Tests-with FeCl3
-Foam Test
•Specific Tests-Keller-Killiani-Salkowski-Baljet-Barfoed-Seliwanoff
General Test: with FeCl3
.Positive ResultA brown ring obtained at the interface indicates the presence of glycosides.
. PrincipleThe brown ring obtained is due to the presence of glycone sugar.
with FeCl3
Specific Tests
Test for Deoxy Sugars
Deoxy sugars are sugars that have had a hydroxyl group replaced with a hydrogen. Keller's reagent describes its use to detect the principal components of digitalis: The reaction with this reagent is also known as the Keller-Kiliani reaction. Lack of the Keller-Kiliani reaction suggests the absence of 2-desoxysugar.
Specific Test: Keller-Killani Test A. Reagents
1.Glacial acetic acid2.Ferric chloride solution3.Concentrated sulphuric acid
B. Materials and Apparatus1.Dropping pipette2.Test tubes
C. Procedure1.Treat five ml of each extracts with 2ml of glacial acetic acid containing one drop of ferric chloride solution. 2.Underlay the mixture with 1 ml of concentrated sulphuric acid. 3.A brown ring of the interface indicates a deoxysugar characteristic of cardenolides. 4.A violet ring may appear below the brown ring, while in the acetic acid layer, a greenish ring may form just gradually throughout thin layer.
Specific Test: Keller-Killani Test
D. Positive Result Presence of brown ring on the interface and greenish ring gradually forms on the upper phase.
E. Principle InvolvedThe brown ring indicates the presence of 2-deoxysugar in the glycone portion of the cardiac glycoside.
Keller-Killiani
Test for Steroidal Nucleus
Steroids are known to perform a variety of functions in higher animals. Steroid nucleus is composed of three six member rings and one five member ring.
Specific Test: Salkowski
A. Reagents
1. Chloroform
2. Sulfuric acid
B. Materials and Apparatus
1. Dropper
2. Test tubes
C. Procedure
1. Add 1ml of the extract to 2ml of chloroform.
2. Carefully add H2SO4. A reddish brown color at the interface indicates
the presence of aglycone portion of cardiac glycoside.
Specific Test: Salkowski
D. Positive Result
Reddish-brown color at the interface
E. Principle Involved
In the Salkowski reaction based method, cholesterol is oxidized in the presence of an excess amount of phosphoric acid and ferric ions to give a reddish brown derivative.
The presence of the aglycone portion of the cardiac glycoside structure is detected. The aglycone part is the portion of the structure where there is the absence of sugar. The change of color into a reddish brown at the interface indicates the aglycone portion of the corchorin.
Salkowski
Test for Lactone Ring
Lactone is a cyclic ester that can be seen as the condensation product of an alcohol group -OH and a carboxylic acid group -COOH in the same molecule. It is identified by a closed ring consisting of two or more carbon atoms and a single oxygen atom, with a ketone group =O in one of the carbons adjacent to the latter. Two classes have been observed in nature - the cardenolides, which have an unsaturated butyrolactone ring and the bufadienolides, which have an a-pyrone ring.
Specific Test: Baljet Test
A. Reagents1. Picric Acid2. Ethanol3. Sodium Hydroxide
B. Materials and Apparatus1.Dropper2.Test tubes
C. Procedure1. To prepare Solution I for Baljet Test, place 1g of picric acid in 100mL of EtOH.2. To prepare Solution II for Baljet Test, add 10g NaOH in 100mL water.3. Combine the two solutions.4. Add 2-3 drops of the combined solution to 2-3mg of sample; a positive reaction is indicated by orange to deep red color.
Specific Test: Baljet Test
D. Positive ResultOrange to deep red coloration
E. Principle InvolvedReactions due to (-CH2-) group of the lactone ring. *cardenolide + Baljet's reagent (picric acid +NaOH) → orange or red.
Baljet
Test for Monosaccharides
Barfoed's Test is a chemical test used for detecting the presence of monosaccharides in a solution. Reducing monosaccharides are oxidized by the copper ion in solution to form a carboxylic acid and a reddish precipitate of copper (I) oxide within three minutes. Reducing disaccharides undergo the same reaction, but do so at a slower rate.
Specific Test: BarfoedA. Reagent
Barfoed’s reagent (mixture of acetic acid and copper (II) acetate
B. Materials1. pipette2. Parafilm3. Test tube4. Hot plate5. Beaker
C. Procedure1. In a test tube, add 1mL of Barfoed’s reagent to 5 ml of the extract.2. Seal the test tube with parafilm so as to prevent volatile substances
from evaporating.3. Place the solution in a boiling water bath.4. When the solution yielded a reaction, remove from the water bath.5. Observe a brick red precipitate indicating the presence of monosaccharides.
Specific Test: BarfoedD. Positive result
Brick red precipitate
E. Principle InvolvedCardiac glycosides contain a sugar portion called glycone and a non sugar portion called the aglycone. The sugar present in Corchorin is olitoribiose. If a reducing sugar is present, a brick red precipitate of Copper (II) oxide is form. The reaction will be negative in the presence of disaccharide sugar as they are weaker reducing agents. One can distinguish monosaccharide from disaccharide based on how fast the brick red precipitate is form. Monosaccharide reacts within 2-3 minutes, whereas disaccharide takes longer. The reaction involved is oxidation in acidic medium.
Specific Test Results
Test Positive Result Obtained Result Photo +/-
Keller-Killiani Presence of brown ring Presence of brown ring +
Salkowski Reddish-brown interface Reddish-brown interface +
Baljet Orange to deep red color Orange to deep red color
+
Barfoed Brick red precipitate Green solution -
Seliwanoff Cherry red solution Yellow -
Anthracene (Anthraquinone) Glycosides
• Anthracene glycosides are oxygenated derivatives of pharmacological importance that are used as laxatives or cathartics, and also as natural
dyes.
1
4
9
10
8
5
Anthraquinone
Reduction
Oxidation
OxanthroneAnthrone
O
O
O
OHH
O
HH
Oxidation
Anthranol
OH
tautomerization
Reduction
The activity decreases as oxidation level increase.
• Forms of Anthracene derivatives in Plants:– Aglycones:
OH OH
CH3HO
O
O
OH OH
CH2OH
O
O
OH OH
CH3
O
O
OH OH
COOH
O
O
RheinChrysophanolEmodin Aloe-emodin
OR OH
COOH
O
OROH
HOOC
O
HH
R= H Sennidin A
R= Glc Sennoside A
R= H Sennidin B
R= Glc Sennoside B
=
=
=
=
Hetero-Dianthrones: The two anthrone moieties are different. e.g. Sennidins C&D and their corresponding glycosides Sennosides C&D. They are all formed of one Rhein and one Aloe-emodin monomers. The C group
are (l)-form while the D group are meso compounds with zero optical rotation.OR OH
CH2OH
O
OROH
HOOC
O
HH
R= H Sennidin C
R= Glc Sennoside C
R= H Sennidin D
R= Glc Sennoside D
=
=
=
=
• Glycosides:– O-glycosides:
e.g. Cascarosides A & B. They are both O- and C-glycosides. Each one contain two sugar unites.
– C-glycosides: e.g. Barbaloin it is formed from the removal of one sugar from Cascarosides.
O OH
CH2OH
O
RR1
Glc
R= Glc, R1= H Cascaroside AR= H, R1= Glc Cascaroside B
OH OH
CH2OH
O
GlcH
Some Drugs containing Anthracene derivatives:
• Senna:• Leaves and pods contain Sennosides A-D.• The C-C bond protect the anthrone from oxidation.
Cascara bark:• Contain Cascarosides A- D.• Barbaloin present as a secondary glycoside in Cascara.• They are O- and C-glycosides.• The C-linked glucose at C-10 protect anthrones from
oxidation.
AloesThe major glycoside in Aloes is the C-glycoside Barbaloin.Barbaloin is primary glycoside in Aloes.The C-linked glucose at C-10 protect anthrones from oxidation.
Mechanism of Action:
• The glycosides are absorbed from the small intestine and re-excreted in the large intestine where they increase the motility so produce laxation.
• Aglycones produce griping effect so it is recommended to prescripe antispasmodic with them.
Chemical test:Borntrager’s and Modified Borntrager’s test:
• For Aglycones:• Extract plant material with organic solvent.• Shake with NH4OH OR KOH.
• For O-Glycosides:• Boil plant material with dil. HCl for 10 min, filter and shake with organic solvent
(Ether or Benzene).• Separate the organic solvent.• Shake with NH4OH OR KOH.
• For C-Glycosides:• Boil plant material with dil. HCl/FeCl3, filter and shake with organic solvent
(Ether or Benzene).• Separate the organic solvent.• Shake with NH4OH OR KOH.
• Positive result indicated by Rose Red colour in the aqueous alkaline layer.
SAPONINS
Saponin Glycosides
Group of organic compounds that form persistent froth when shaken with water.
Saponins cause haemolysis of red blood cells.
The word Soap means Soap like.
Properties:• Soluble in water, alcohol and mixture of them.• Form persistent froth with water.• Used as detergent and emulsifying agents.• Aglycones are called Sapogenin.• Cause haemolysis of RBC’s if reach the blood.• Form complex with cholesterol.• Only small part absorbed when taken orally.• Enhance the absorption of other drugs.
Classification:• According to the nature of the aglycone saponins are
classified into Steroidal and Triterpenoidal saponins.
Sug-OSug-O
Triterpenoidal SaponinsSteroidal Saponins
Steroidal Saponins
• They are C-27 with 5 methyl groups.• Less distributed in nature comparing to
Triterpenoidal saponins.• Used mainly as precursors for the partial
synthesis of sex hormones and corticosteroids.• Drugs containing Steroidal saponins such as:
– Discoria species Diosgenin– Sarsaparilla Roots Sarsapogenin
Steroidal Saponins• Also called tetracyclic
triterpenoids
• Found in many monocotyledons such as Wild yam (Dioscorea vilosa).
• Saponin – Diosgenin.
• Also found in dicotyledons fenugreek.
• Strophanthus and Digitalis contain both steroidal saponins (glycosides) and cardiac glycosides.
Significance of Steroidal Saponins• Generate much interest due
to their relationship with compounds such as sex hormones, cortisone, diuretic steroids, vitamin D and the cardiac glycosides.
• Some are used as starting materials for the synthesis of these compounds.
• Diosgenin is the main sapogenin used by industry .
Ginseng Saponins(Ginsenosides)
• Source: Roots of Panax ginseng
• Nature: They are C-30 compounds but they have typical Steroidal skeleton.
• Classification: a- Protopanaxdiolsb- Protopanaxtriols
OH
Sug-O
OH
Sug-O
O-Sug
Sug-OSug-O
Protopanaxdiols Protopanaxatrion
Uses:• It has an adaptogenic (antistress, anti-fatigue)
effect. • It improves both physical and mental
performance including learning, memory and physical capabilities.
• It improves the immune function and metabolism.
• Improve liver functions.• Stabilize blood glucose and blood pressure.
Triterpenoidal Saponins(Pentacyclic triterpenoid saponins)
• They are C-30 compounds.
• Much more distributed in nature.
• Have pentacyclic skeleton with 8 methyl groups.
Liquorice• Source: Glycyrrhiza glabra.• Constituents: Sweet triterpenoidal saponins “Glycyrrhizin”.
• Uses:– Flavoring agent in Pharmaceutical preparation.– Demulcent and expectorant.– Treatment of peptic ulcer.– Treatment of Rheumatoid arthritis and Inflammatory conditions as
it has cortisone like action.– Sweetener– Treatment of liver diseases and liver protection
COO-
OGlcGlc
O
Glycyrrhetic acid
Glycyrrhizinic acid
Glycyrrhizin
3- Senega
• Source: Senega roots.• Constituents: Triterpenoidal saponins “Senegin II”.
• Uses:– Stimulant expectorant in chronic bronchitis.
COOH
CH2OH
HO
RO
COOH
Cyanophore (Cyanogenic) Glycosides• Glycosides that yield hydrocyanic acid (HCN) on
hydrolysis• common glycosides are derivatives of
mandelonitrile (benzaldehyde - cyanohydrin)1. Amygdalin ------- mandelonitrile (aglycone)
• prunasin
2. Sambunigrin ------- S - mandelonitrile (aglycone)
• accompanied by enzymes (β-glucosidases) that catalyze reactions
amygdalin glucose + prunasin glucose +
mandelonitrile HCN + benzaldehyde
Cyanogenic Glycosides Cyanogenic glycosides (Cyanogentic or Cyanophore
Glycosides) are O-glycosides yielding HCN gas on hydrolysis .
They are condensation products of HCN to a carbonyl compounds (Cyanohydrin).
C
R
R
O C
R
R OH
CN
HCNC
R
R O-Sug
CNGlycosylation
Unstable Stable
1- AmygdalinSource: Bitter Almond.Structures: It is a Bioside of mandilonitril.
CH
CN
O glc glc
CH
CN
O glc
Amygdalin Prunasin
1-6 linkage
CH
CN
O H
Mandilonitril
CHOHCN +
Amygdalase Prunase
2- LinamarinSource: Linseed.Structures: It is the glycosidic derivative of the cyanohydrin of
acetone.
Uses:Linamarin has a molluscecidal activity.Amygdalin is used for the preparation of Benzaldehyde.Cyanogenic glycosides have role in cancer treatment.
C
H3C
CNH3C
O glc
Test for Cyanogenic Glycosides:
• Reduce plant material to small pieces and moisten with water.
• Incubate at temp. less than 45 0C for 30 60 mins with the neck of the flask stoppered and have suspended sodium picrate paper.
• The paper will turns brick red due to the release of HCN gas.
Wild Cherry USP XVIII (1970)Synonym: wild black cherry, Virginian prune
bark, rum or whisky barkOrigin: carefully dried stem bark of Prunus
serotina (Rosaceae)- also known as Prunus virginiana (wild black cherry tree)
Constituent: prunasin ---partial H+---- HCNp-coumaric acid, trimethyl gallic acid
Use: flavoring vehicle (cough remedies)sedative expectorant, antitussive, astringentused for colds, bronchitis, whooping cough
Adverse: fatal poisoning when ingested in large amounts
Black Mustard NF XI (1960) Synonym: brown or chinese mustard, Sinapis nigraOrigin: dried ripe seed of Brassica nigra or B. juncea (Brassicaceae)Constituent:
sinigrin ---H+---- allyl isothiocyanate + KHSO4 + glucose- sinigrin (potassium myronate)- allyl isothiocyanate (mustard oil - volatile)
Use: local irritant, emetic, externally: rubefacient, pulmonary congestion, rheumatic arthritiscommercial: condiment
Flavonoids (or bioflavonoids) (from the Latin word flavus meaning yellow, their colour in nature) are a class of plant secondary metabolites.Flavonoids were referred to as Vitamin P (probably due to the effect they had on the permeability of vascular capillaries) from the mid-1930s to early 50s, but the term has since fallen out of use.According to the IUPAC nomenclature, they can be classified into:flavones: derived from 2-phenylchromen-4-one (2-phenyl-1,4-benzopyrone) structure (examples:quercetin, rutin).isoflavonoids, derived from 3-phenylchromen-4-one (3-phenyl-1,4-benzopyrone) structureneoflavonoids, derived from 4-phenylcoumarine (4-phenyl-1,2-benzopyrone) structure
Core structures and nomenclature
• The nomenclature of flavonoids proper is straight-forward with the aromatic ring A condensed to the heterocyclic ring C and the aromatic ring B most often attached at the C2 position. The various substituents are listed first for the A and C ring and - as primed numbers - for the B ring (note that the numbering for the aromatic rings of the open-chained precursor chalcones is reversed).
O O
O O
OH
O
OH
O O
O O
OH
O
OH
+
Flavanone Dihydroflavonol Flavan-3-ol
Flavone Flavon-3-ol Anthocyanidin
O
OH
Chalcone
A
B
O
O
Isoflavone
O
Neoflavone
A
B
C
The three flavonoid classes above are all ketone-containing compounds, and as such, are flavonoids and flavonols. This class was the first to be termed "bioflavonoids." The terms flavonoid and bioflavonoid have also been more loosely used to describe non-ketone polyhydroxy polyphenol compounds which are more specifically termed flavanoids, flavan-3-ols (or catechins).
Functions of flavonoids in plantsFlavonoids are widely distributed in plants fulfilling many functions.Flavonoids are the most important plant pigments for flower coloration producing yellow or red/blue pigmentation in petals designed to attract pollinator animals.In higher plants, Flavonoids are involved in UV filtration, symbiotic nitrogen fixation and floral pigmentation.They may act as a chemical messenger or physiological regulator, they can also act as cell cycle inhibitors.Flavonoids secreted by the root of their host plant help Rhizobia in the infection stage of their symbiotic relationship with legumes like peas, beans, clover, and soy. Rhizobia living in soil are able to sense the flavonoids and this triggers the secretion of Nod factors, which in turn are recognized by the host plant and can lead to root hair deformation and several cellular responses such as ion fluxes and the formation of a root nodule.
Potential effects on human healthFlavonoids (specifically flavanoids such as the catechins) are "the most common group of polyphenolic compounds in the human diet and are found in plants Flavonols, the original bioflavonoids such as quercetin, are also found ubiquitously, but in lesser quantities.The widespread distribution of flavonoids, their variety and their relatively low toxicity compared to other active plant compounds (for instance alkaloids) mean that many animals, including humans, ingest significant quantities in their diet. Preliminary research indicates that flavonoids may modify allergens, viruses, and carcinogens, and so may be biological "response modifiers". In vitro studies show that flavonoids also have anti-allergic, anti-inflammatory, anti-microbial, anti-cancer, and anti-diarrheal activities.
Antioxidant activity in vitroFlavonoids (both flavonols and flavanols) are most commonly known for their antioxidant activity in vitro. At high experimental concentrations that would not exist in vivo, the antioxidant abilities of flavonoids in vitro may be stronger than those of vitamin C and E, depending on concentrations tested.Consumers and food manufacturers have become interested in flavonoids for their possible medicinal properties, especially their putative role in inhibiting cancer or cardiovascular disease. Although physiological evidence is not yet established, the beneficial effects of fruits, vegetables, tea, and red wine have sometimes been attributed to flavonoid compounds.
Potential anti-cancer activityFlavonoids might induce mechanisms that affect cancer cells and inhibit tumor invasion. In preliminary studies, Some cancer researchers proposed that smokers who ate foods containing certain flavonoids, such as the flavan-3-ols (catechins) found in strawberries and green and black teas, kaempferol from brussel sprouts and apples, and quercetin from beans, onions and apples, may have reduced risk of developing lung cancer.
Example flavonoidsQuercetinQuercetin, a flavonoid and more specifically a flavonol, is the aglycone form of other flavonoid glycosides, such as rutin and quercitrin, found in citrus fruit, buckwheat and onions. Quercetin forms the glycosides, quercitrin and rutin, together with rhamnose and rutinose, respectively. Although there is preliminary evidence that asthma, lung cancer and breast cancer are lower among people consuming higher dietary levels of quercetin, the U.S. Food and Drug Administration (FDA), EFSA and the American Cancer Society have concluded that no physiological role exists. The American Cancer Society states that dietary quercetin "is unlikely to cause any major problems or benefits.
EpicatechinEpicatechin may improve blood flow and has potential for cardiac health. Cocoa, the major ingredient of dark chocolate, contains relatively high amounts of epicatechin and has been found to have nearly twice the antioxidant content of red wine and up to three times that of green tea in vitro. In the test outlined above, it appears the potential antioxidant effects in vivo are minimal as the antioxidants are rapidly excreted from the body.Good sources of flavonoids include all citrus fruits, berries, ginkgo biloba, onions (particularly red onion, parsley, pulses, tea(especially white and green tea), red wine, seabuckthorn, and dark chocolate (with a cocoa content of seventy percent or greater).
The citrus bioflavonoids include hesperidin (a glycoside of the flavanone hesperetin), quercitrin, rutin (two glycosides of the flavonolquercetin), and the flavone tangeritin. In addition to possessing in vitro antioxidant activity and an ability to increase intracellular levels of vitamin C, rutin and hesperidin may have beneficial effects on capillary permeability and blood flow. They also exhibit anti-allergy and anti-inflammatory benefits of quercetin from in vitro studies. Quercetin can also inhibit reverse transcriptase, part of the replication process ofretroviruses. The therapeutic relevance of this inhibition has not been established. Hydroxyethylrutosides (HER) have potential for use in the treatment of abnormal capillary permeability, bruising, hemorrhoids, and varicose veins.
hesperedinOrigin: rind of unripe citrus fruits
synonym: hesperetin - 7 - rutinoside or hesperetin ,- 1 -rhamnoside - d - glucoside
- methyl eriodictyol
hesperedin --H+ --- hesperetin + rutinose
Use: necessary for the retention of Vit C, catalyzes Vit C and protein to maintain normal capillary resistance (reduce capillary fragility)
- for common colds
Coumarin chemical compound in the benzopyrone chemical class, found in manyplants, notably in high concentration in the tonka bean (Dipteryx odorata), vanilla grass (Anthoxanthum odoratum), sweet woodruff ( Galium odoratum), mullein (Verbascum spp.), sweet grass (Hierochloe odorata), cassia cinnamon (Cinnamomum aromaticum), melilot(Melilotus ssp.), Panicum Clandestinum or 'Deers Tongue'
GYCOSIDAL BITTERS:These are the substances taken before meal to improve the appetite. These glycosides do not belong to the same chemical class but most of the drugs contain monoterpene irridoids with pyran cyclopentane ring. These have the stimulant effect on gustatory nerves in the mouth and lead to increase the gastric juice secretions. The drugs which contain these are:Genatin, Picrorrhiza, Chirata, Quasia, Kalmegh
