A brief details on flavonoids

This PPT include the description of flavonoids which is useful for pharmacognosy students. It include flavonoids description, classification and identification test.

1. FLAVONOIDS
PREPARED BY:
MS. DIPTEE GUPTA
ASSISTANT PROFESSOR
KRISHNA INSTITUTE OF PHARMACY & SCIENCES,
KANPUR

2. INTRODUCTION
•Phytochemical compounds present in many plants, fruits,
vegetables, and leaves.
•They are typically yellow pigments found in the majority of
plant species.
•Approximately 4000 flavonoids have been isolated and
identified.
•These are products of secondary metabolites of plants, which
mainly consist of a benzopyrone ring having phenolic or
polyphenolic groups at different positions.

3. GENERAL STRUCTURE OF FLAVONOID
•Thechemicalstructureofflavonoidsisaskeletonofdiphenylpropane,
i.e.,
•Twobenzenerings(ringsAandB)linkedbyathree-carbonchainthat
formsaclosedpyranring(heterocyclicringcontainingoxygen,theC
ring)withthebenzenicAring.
•Therefore,theywererepresentedasaseriesofC6-C3-C6compounds.

4. PHYSICAL PROPERTIES OF FLAVONOIDS
•Crystallinesubstanceswithdefinitemeltingpoint.
•Somearecolourlesscrystalsuchascatechins,flavanes,isoflavanes,flavanones,
flavanonoleswhereasflavones,flavonols,chalconesareyellowcoloured
crystals.
•Anthocyanidinsareredinacidicmediaandblueinalkalinemedia.
•Flavonoidglycosidesaregenerallysolubleinwaterandalcoholbutinsolublein
organicsolvents.Aglyconepartsofflavonoidsaresolubleindiethylether,
acetone,alcoholsetc.
•Opticallyactive.
•UndertheUVlightflavonoidsshowsfluorescenceofdifferentcolours(yellow,
orange,brown,red).

5. CLASSIFICATION OF FLAVONOIDS
•Flavonoids can be broadly classified into multiple classes on the basis of
various parameters such as;
✓Degree of unsaturation,
✓On the carbon of the C ring on which B ring is attached,
✓Oxidation of the C ring
✓glycosylation pattern.
The most widely accepted classification system is based on the location of B-
ring. On this basis flavonoids are divided into three groups as following:
•1.Bio-flavonoids (true flavonoids)
•2.Iso-flavonoids (phytoestrogens)
•3.Neo-flavonoids (white-flavonoids)

6. 1. BIO-FLAVONOIDS
•These are flavonoids in which the B-ring is attached to position 2 of the C-
ring and further subdivided on the structural properties of the C-ring.
S.No.SubclassesofBio-
Flavonoids
Properties Examplewithbiologicalsource
1. Flavones Ithasadoublebondbetweenpositions2and
3andaketoneinposition4oftheCring.
Mostlyfoundinfoodssuchascelery,lettuce
andcapsicumpeppers
Apigenin(Apiumpetroselinum)
Luteolin(TomentosaSalvia)
2. Flavonols Ithasahydroxylgroupinposition3oftheC
ring,whichmayalsobeglycosylated.
Quercetin(Quercusalba)
Kaempferol(Pinussylvestris)
Myricetin(Rosadamascene)
Fisetin(Fragariaananassa)
3. Flavonones
(Dihydroflavones)
IthastheCringsaturatedandthedouble
bondbetweenpositions2and3issaturated.
Foundinalmostallcitrusfruitsandare
responsiblefortheirbittertaste.
Hesperidin(Citrussinensis)
Naringenin(Citrusparadise)

7. 2. ISO-FLAVONOIDS (PHYTOESTROGENS)
•TheseareflavonoidsinwhichBringisattachedtoposition3onthec-
ring.
•Thestructureofiso-flavonoidsissimilarto17-βestradiolaswellasbinds
tooestrogenreceptors.Duetothisproperty,theyarealsoknownas
phytoestrogens.
•Thesehavehighpotentialagainstvariousdiseasessuchasosteoporosisand
cardiovasculardisease.
Exampleofiso-flavonoidsasfollows:
Genistein,daidzein,glycitein,(glycinemax)orsoyabean,Formononetin
(astragalusmembranaceus)

8. NEO-FLAVONOIDS
•TheseareflavonoidsinwhichB-ringisattachedtoposition4ofthec-ring.
•Itpossessespharmacologicalactionsuchasanti-allergic,anti-inflammatory,
anti-osteoporotic,antimicrobialandanti-oxidant.
•Exampleofneo-flavonoidsasfollows:
•Calophyllolide(Calophylluminophyllum)
•Dalbergin(Dalbergiasissoo)
•Nivetin(Echinopsniveus)

9. IDENTIFICATION TEST
1.Shinodatest:
Alcoholicsolutionofflavoneorflavonoltreatedwithmetallicmagnesium(or
zinc)andHClgivesanorange,redorvioletcolour.Thistestisalsoknownas
cyanidinreaction.
2.Leadsubacetatetest:
Tosmallquantityofresidue,addleadsubacetatesolution.Yellowcoloured
precipitateisformed.Additionofincreasingamountofsodiumhydroxideto
theresidueshowsyellowcolouration,whichdecolourationafteradditionof
acid.

10. CONTI….
3. Wilson’s reaction:
Flavonoids form complexes with boric acid which is not destroyed by addition
of citric acid alcoholic solution (or oxalic acid).
4. Antimony pentachloride test:
Alcoholic solution of sample reacts with antimony pentachloride. The solution
produces red or violet colour.

11. FUNCTIONS OF FLAVONOIDS
•Theyareresponsibleforcolorandaromaofflowers.
•Theyattractinsectsforpollinationandhelpinseeddispersion
•Theyprotectplantsfromdifferentbioticandabioticstressesandactasunique
UVfilters.
•Theyactaspowerfulantioxidantslikequercetin,xanthohumol,isoxanthohumol
etc.
•Theyactasplantgrowthregulator.
•Theyalsofunctionasfungicidestoprotecttheplantfromfungalinfection.

12. Thank You