Plant Glycosides Flashcards
glycosides contain a sugar molecule and a non-sugar molecule called an
aglycone
there are 4 ways in which the sugar and aglycone are linked those include:
- C glycosides
- Carbon/carbon bond
- resist acid and base hydrolysis
- O glycosides
- linked by oxygen, stable in acid solution
- acid or enz hydrolysis
- N glycosides
- linked by amino group
- S glycosides
- linked through S atom, usually thiol group
what is the most prominant type of glycosides in nature are
O-glycosides
the sugars found in glycosides are generally
- 4-5 carbon sugars
- in alpha or beta form (most beta)
- primarily glucose, can also include rhamnose or galactose
the role of the sugar in glycosides is primarily to
- aid in absorption
- protect the aglycone moiety from premature metabolism
the number of sugars in the molecule impact these three things
- polarity, solubility and chromatographic characteristics
glycosides are commonly extracted with
- dilute alcohol solutions
- freed from contaminants by lead acetate precipitation
- and individual components isolated by preparative chromatography
there are 5 groups of glycosides based upon the aglycone group present, these four groups are
- cyanogenetic glycosides
- Isothiocyante glycosides
- Antrhacene glycosides
- Phenol glycosides
- steroid glycosides
phenol glycosides are further subclassed to include these four groups
- simple phenols
- phenolic acids
- flavanoids
- coumarins
steriod glycosides include these 4 subcategories
- cardenolides
- bufadienolides
- steroid saponins
- triterpene saponins
cyanoglycosides have this effect in humans
poisonous
what are examples of plants that contain cyanide
- the seeds of apricots, peaches, cherries and almonds
- cassava
what are the glycosides from almonds, cherry bark and linseed that are considered poisonous
- amygdalin
- prunasin
- linamarin
what are cyanogentic glycosides commonly used for
flavouring agents with expectorant properties
Anthracene glycosides are commonly used as (2 things) and include the following sources (5)
- laxatives or purgatives
- cascara, senna, frangula bark, rhubarb, aloe
anthracenes are 3 fused rings of
benzene
two common glycosides from senna and cascara are
sennosides
cascarosides
anthracene glycosides are in the
- leaves, fruits, barks, rhizomes or juice of plants
what is the mecahnism of action of anthrcene glycosides
- more active as anthrone glycoside than free anthriquinone
- prevents metabolism of the molecule until it reaches the colon where it gradually releases the anthrone stimulating the intestine to act, in the case of sennosides, defecate
what is the most active anthracene
sennosides
what assay is used to assess anthracene glycosides
- qualitative colour test called Borntragers test
- pink red colour obtained when anthraquinone form reacts with alkali
- intensity of colour directly proportional to concentration of anthraquinone
what are two analytical challenges in trying to assay senna
- separation of sennoside from inactive anthraquinone is difficult, giving higher values
- conversion of the dianthrone to quinone
how is the assay for senna performed
- extract into ether
- react with magnesium acetate
- measure in spectrophotometer against standard or calibration curve
phenolic glycosides include (5)
- simple phenols
- tannins
- flavanoids
- coumarins
- lignans
simple phenols have wide pharmacological activity including (5 properties)
- antibacterial
- anti-inflammatory
- antipyretic
- antiemetic
- antivrial and antirheumatic
thymol is isolated from ________plant and has this pharmacological effect
rosemarinic acid is isolated from ________plant and has this pharmacological effect
- thyme & antibacterial
- lemon balm, rosemary and comfrey & antiviral and anti-inflammatory
what is the mechanism of action of rosemarinic acid
- inhibits classical and alternative pathways of complement activation and
- scavenges toxic oxygen from activated polymorphonuclear leucocytes
- antiviral activity - inhibits binding of virus to host cell
this group of phenolic glycosides are polymers of simple phenols
tannis
tannins can cross link with protein in animal skin to form leather, how is the action of significance for its clinical use
- it provides a barrier to infections for wounds or burns allowing the healing process to occur
what are two categories of tannins
- hydrolysable and condensed aka proanthrocyanidins
what are some concerns over tannins in herbal teas. Are these concerns valid, why?
- may interfere with drug absorption or minerals/vitamins
- carcinogenic effects
- not valid because regular tea has more tannins than herbal tea
flavanoids are the smallest or largest group of naturally occurring phenols
largest
most flavanoids exist as C,O,N, or S glycosides
O and C
this group of glycosides is found universally in plants
flavanoids
flavanoids have these properties (4)
- antiallergic - Quercetin
- antispasmotic - Chamomile
- cardiotonic - hawthorn
- cerebrovasular - Gingko
what is the mechanism of action of the flavanoid quercetin
- inhibition of lipoxygenage, inhibits release of leukotrienes from mast cells
this group of phenolic glycosides are Benz - alpha-pyrones
coumarins
coumarins have these physiological effects
- inhibt grouwth of bacteria, yeast fungi
- anticoagulant effect
Lignans are complex dimeric molecules containing
two phenylpropanoid units linked by a C-c bond
what is the best known lignan
podophyllotoxins
podophyllotoxins possess this physiological effect
name two podophyllotoxins
- cytotoxic
- etoside and teniposide are used in chemotherapy
what are three classes of steroid glycosides
- Cardiac Glycosides
- Steroid Saponins
- Triterpene Saponins
steroid glycosides are produces via which pathway
mevalonic
cardiac glycosides have this effect
increase pumping action of heart
what is the source of the most important cardiac glycoside
- digitalis (foxglove) e.g. digoxin
- also adonis, oleander, and lily of the valley
cardiac glycosides contain two aglycones that are cardioactive
- cardiotonic and cardiotoxic glycosides
cardiac glycosides can be subcategorized as
- cardenolides and
- bufadienolides
cardiac glycosides contain this number of carbons
C23 or C24
this is the primary aglycone in cardiac glycosides
cardenolides
cardenolides contain this type of lactone ring and Bufadienolides contain this type of lactone ring
- C5
- C6
sugar moieties found in cardiac glycosides are (4 - two of which are primarily found)
- digitose*
- cymerose*
- glucose
- rhamnose
Digitalis glycosides contain this number of glycosides
5
vary with number of OH groups
purpea glycosides are also known as
deslanosides
what is the activity of glycosides due to
the presence of a lactone ring
what is the key element in the attachment of the glycoside to the receptor
carbonyl functional unit of the lactone ring
effectiveness of glycoside is depenent upon
sugars which make the glycoside more soluble and assist in binding to cardiac muscle
Digitoxin is most widely used because
it is more rapidly absorbed from G.I.T than purpurea glycosides
Bufadienolide glycosides are less widely used becaus of
toxicity
what plant contains bufadienolides
squill
Chemical assays for cardiac glycosides are based on
chromogenic ID tests
which reagent is used in TLC separation of digitalis glycosides
Kaiser’s reagent
this reagent is most commonly used
baljet test detects lactone ring
Saponin glycosides are water soluble and have these common characteristics making them easily identifiable
- cause frothing by reducing surface tension
- hemolyze RBCs by forming a complex with cholesterol from the RBC wall
- paralyze fish gills
what are the two types of sapogenins (aglycones) in saponin glycosides
- steroidal
- triterpenoidal
steroidal saponins are isolated from ______while triterpene saponins are isolated from________
- monocots such as agave
- dicots such as yams
which is the most widely used sapogenin
Diosgenin from mexican yam
what are steroidal glycosides commonly used for
precursors for steroidal hormones such as cortisone, estrogens, progesterones etc
two main types of triterpenoid saponins include
- tetracyclic triterpenese (trimethylsteroids) C27
- pentacylic triterpenes (C30)
pentacyclic triterpenoidal saponin glycosides include these four series of sapogenins. which is the most significante
- ursane
- hopane
- lupane and
- oleanane series*
Oleanane sapogenins are isolated from
senega, primrose, horse chesnut and quillaia ivy
triterpenoidal saponins have these physiological effects
- antimitotic
- anti-cancer
- anti inflammatory
- analgesic
- antipyretic
- anti ulcerogenic
- sedative
- cardiac
- antithrombotic
- molluscicidal
- spermicidal
aescin from horse chestnut is used for treatment of_________because of its _______effect
- hemorrhoids
- antagonist effect on edema of blood vessels
an important triterpenoid is______because of its _________properties it can be used to treat this parasitic disease
- ginsing
- molluscidal
- schistosomiasis
ginsing is sourced from leaves of__________and is widely used because of its_________effects
- panax ginseng
- protective effects on the body against fatigue and stress, slowing down the degenerative effects of ageing
liquorice root contains the glycoside__________which is used to treat___________
- glycrrhizin
- ulcers and inflammation
what are some common side effects of glycrrhizin
- hypertension
- adreno and mineral corticoid activity