phytochemistry
Lecture 18
Flavonoids
Date : 14/4/2015
done by: Fatima aldiqs
-Most flavonoids are found as glycosides few as aglycons.
-In extraction in last step we will have free sugars and most polar glycosides (they can’t be
removed from water even using hot ethyl acetate).
-After that we must make separation before quantitative and qualitative analysis to avoid
interference.
- TLC technique: qualitative for identification (one of the most efficient supportive tools for
identification), using reference standard, spotting on the plate, match between reference and
our analyte , we match two things: RF value (retardation factor : distance travelled by analyte
relative to solvent) and color development (usually we spray the plate with spraying agent
interact with analytes spots and give color subs although flavonoids are already colored subs
and can visualize by naked eye this is the visualization step)
Visualization is: 1.direct, like chalcones , aurones and anthocyanidins Or you can increase the
intensity of color using ammonia vapor...b\c ammonia is a base and phenols or flavonoids are
acids >>ionization >> increase resonance in those aromatic compounds >> more intense color
To summarize visualization: 1.without any chemical treatment (day light or under UV)
2. with chemical treatment
-One of the most techniques used: separation...Spraying...Drying by air dryer (to dry solvent
and temperature will help in the chemical Rxn to produce a color)
Note: with or without treatment aurons are always more intense in color compared to
chalcones
-spraying with Al trichloride: make further conjugation and more stable structure – more rigid
>> give fluorescence rather than thermal energy “dissipiation”.
Quantitative”assay”: 1- calorimetric: add reagent to the subs to have colored complex this
complex is what we measure actually and by the molar ratio we know how much drug we have
>>.colored complex used to increase absorptivity .
2- spectrophotometry: without color treatment >> most subs have enough chromophore to be
detected.
3- HPLC: the most used b\c it separate and quantitate (have UV detector).
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phytochemistry
Phase used in HPLC are C8 and C18 “most commonly used”.
BP: use extraction in assay (use HPLC less than USP
USP: use HPLC much more
Biological properties
-The most important function of overall flavonoids that are free radical scavengers – anti
oxidant substances so the main target they work on is the vascular system(in case of any
pathological condition that may caused by free radical’s attack>>weaken the vessels>>highly
permeable>>edema ,hemorrhage ..)
-Tissue repair and building since they induce collagen synthesis -important structural proteins
especially in vascular tissue.
-Also they act as enzymes inhibitors, ant inflammatory...so they compact events following
tissue injury.
Enzymes inhibitors:
inhibition of these enzymes is associated with increase tonicity ,integrity ,strength ,reduce
bleeding
1. histidine decarboxylase, elastase >>these enzymes destroys membranes (and hyaluronidase
destroys membranes in neuronal tissues and myelin sheath), 2. Catechol-o-methyl transferase
destroy catecholamine which are sympathomimetic “vasoconstrictors” >>so inhibition of it will
increase tonicity, 3.cAMP phosphodiesterase which involved in platelets aggregation
>>inhibition of it will exert anti platelet effect)
4. Inhibit lypoxygenase >>anti-allergic, inhibit cyclooxygenase >>anti-inflammatory –like aspirin
but in different mechanism -flavonoids called vitamin P factors b\c they decrease hyper permeability associated with
weaken and fragile vessels – vitamin C like action ( related to antioxidant action) - ,also they
found in plant parts and plant species rich in Vit c like citrus species ‫( –الحمضيات‬lemon ,orange,
grape fruit …in the endocarp ,fruits ,core…)
Anti-oxidant scavenging function of flavonoids is highly associated with hydroxylation on ring B that’s
why Quercetin which has 2 hydroxyl functions at 3’ and 4’ ortho hydroxylation is one of the strongest
anti-oxidants
- in plant :
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phytochemistry
-help in pollination so plant survival and reproduction
-there rule as growth hormone regulators ,induce GH release by increasing indol acetic acid to
indol acetic acid oxidase ratio (IAA\IAA-oxidase) - in other words they inhibit indol acetic
acid oxidase>> induce plant growth
- have 2 protective rules in plant:
1. Found in epidermis so absorb damaging UV (especially UV-A)
2. they are Phytoalexin: is subs produced by plant in response to a pathological event
especially infections >> so they are antifungal and antiviral.
-
The overall function of flavonoids : vascular protective agents and venous tonics (
increase tonicity)
Vitamin c deficiency = scurvy disease: ‫ االسقربوط‬continuous oxidative damage status
>venous insufficiency>>highly permeable venous system especially lower
limbs>>edema, pain
Can be treated by vit c and flavonoids rich subs (rutin ,Hespiridin ,diosmin)
-Flavonoids usually doesn’t used alone they prepared in combination with other drug
subs b\c they in overall enhance the effect of drug and help improve the conditions of
the patient and relief symptoms especially that are associated with vascular disease so
they are not a direct treatment.
-They relieve symptoms of influenza
-uses of flavonoids containing drugs mentioned in slide 32
*Citroflavonoids :called b\c they found in citrus species rotaceae family
-One of the most important flavonoids in markets, include:
1. Flavanone glycosides (no double bond): naringin ,eriodyctin,hesperidin,neohesperidin
2. Flavone glycosides: rutin ,diosmin
These glycosides named according to the aglycon :
Ex: naringin from the aglycon naringenin ( trihydroxyflavanone )
Eriodyctin from the aglycon Eriodictyol (tetrahydroxy flavanone)
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phytochemistry
Hesperidin from aglycon hesperetin ( hesperetin Is eriodictyol but have methyl group
= 4’-methyleriodictyol )
Note: you gived the hesperetin structure –in slide34- , where the sugar (rutinose) will
condense? *On C7 since C3 have no OH
- diosmin from aglycon diosmetin substituted by rotinose on C7 (diosmetin derived from the
simplest flavone apigenin , = 4’-methylapigenin)
(hesperidin and diosmin are rutinosyl derevatives from there aglycons)
-Rutin from quercetin (sugar substituted on C3).
Good luck ^_^
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