PowerPoint Presentation• A pleasant-smelling colourless crystalline compound, m.p. 70°C.
• It is released by many cut plants, especially grasses, with a fresh delightful
smell usually called ‘new mown hay’.
• Coumarin is also present in some herbs such as lavender
• It occurs naturally in tonka (or tonquin) beans, and is synthesized from
salicylaldehyde.
• Coumarin is also found naturally in many edible plants such as
strawberries, black currants, apricots, and cherrie 1
• It forms coumarinic acid on hydrolysis with sodium hydroxide.
• Coumarin is used in making perfumes, to scent tobacco, and as an
anticoagulant in medicine; *warfarin is derived from it.
• It has appetite-suppressing properties, which can discourage animals
from eating plants that contain it. Though the compound has a pleasant
sweet odor, it has a bitter taste, and animals tend to avoid it
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It contains a benzene ring and an -pyrone fused together.
coumarin – the smell
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• Most can be recognized by the aromatic
ring joined to a three-carbon atom side chain.
• Two simple examples are coumarin, responsible
for the smell of mown grass and hay, and umbelliferone, which
occurs in many plants and is used in suntan oils as it absorbs UV
light strongly.
Clayden - Organic chemistry by Clayden, J. et al 4
• Coumarin has an odor that is often described as “new-mown hay”
or “woody” and is used in men’s toiletries.
• Along with vanillin it is a component of natural vanilla.
• A combination of these two compounds, prepared synthetically in
the laboratory, is used in artificial vanilla, and the flavoring in
cream soda consists of coumarin and vanillin.
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Coumarin and its derivatives are all known as phenylpropanoids.
Some naturally occurring coumarin derivatives are:
umbelliferone (7-hydroxycoumarin),
aesculetin (6,7-dihydroxycoumarin),
herniarin (7-methoxycoumarin),
4-Phenylcoumarin is the backbone of the neoflavones, a type of
neoflavonoids.
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brodifacoum, bromodiolone, difenacoum and auraptene.
Coumarin is transformed into the natural anticoagulant dicoumarol by a number
of species of fungi.
This occurs as the result of the production of 4-hydroxycoumarin, then further
(in the presence of naturally occurring formaldehyde) into the actual
anticoagulant dicoumarol, a fermentation product and mycotoxin.
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Uses Medicine
Warfarin – a coumarin – with brand name, Coumadin, is used as an
anticoagulant to impede formation of blood clots, and a treatment for deep
vein thrombosis and pulmonary embolism.
Rodenticide precursor
Coumarin is used in the pharmaceutical industry as a precursor reagent in the
synthesis of a number of synthetic anticoagulant pharmaceuticals similar to
dicoumarol. 8
Laser dyes
Coumarin dyes are extensively used as gain media in blue-green tunable
organic dye lasers.
Perfumes and aromatizers
It is still used as a legal flavorant in soaps, rubber products, and the
tobacco industry, particularly for sweet pipe tobacco and certain alcoholic
drinks.
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CHROMANS
The compound in which benzene ring is 0-fused to a 4H-pyran
ring is known as 4H-Chromene. Its dihydro-derivative is
chroman, an oil, with a p.b. 215 C(488k), which is volatile in
steam and has a peppermint like odour.
O
4H-Chromene
Chroman
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O
O
hydroxyflavone (flavanol) are more important than the parent
compound.
Chromone
Flavone
• Chromene is isomeric with coumarin (benzo-α-pyrone).
• A series of derivatives containing further hydroxy groups occur as yellow
pigments in flowers, wood and roots.
• Quercetin, 3, 5, 7, 3, 4-pentahydroxy flavone, is the most important
plant pigment of this sort. It occurs in the bark of the American oak,
Quercus velutina as an L-rhamnoside, bonded at the 3-position.
• It also occurs either in the free state or bonded as a glycoside in many
plants, for example in the flowers of wallflowers, roses, and also in tea
and hops. 13
benzo-γ-pyrone framework.
• Chromones and their structural analogs are of great interest because of
their usefulness as biologically active agents.
• They have been shown to be tyrosine and protein kinase inhibitors, as
well anticancer, neuro protective, anti-AIDS,
antimicrobial, antifungal, antioxidant activity, and antiproliferative agents.
• Chromones may also have application in cystic fibrosis treatment.
Chromones derivatives could also be useful for other applications in
medicinal chemistry such as preparation of fluorescence probes due to the
phytochemical properties of chromenes.
Flavones are a class of flavonoids based on the backbone
of 2-Phenylchromen-4-one (2-phenyl-1-benzopyron-4-
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• They occur mainly in cereals and herbs, they are a class of plant
secondary metabolites.
• Chemically they have the general structure of a 15-carbon skeleton,
which consists of two phenyl rings (A and B) and an heterocyclic
ring(C).
• The Carbon structure can be abbreviated as C6-C3-C6.
• They can be classified into 3 classes according to IUPAC nomenclature
as follows:
benzopyrone) structure.
benzopyrone) structure
• The three flavonoid classes above are all ketone containing
compounds and as such are anthoxanthins (flavones and flavonols).
• The terms flavonoid and bioflavonoid have been more loosely used to
describe non-ketone polyhydroxy polyphenol compounds which are
specifically termed flavonoids.
• The three cycles or heterocycles in the flavonoid backbone are
generally called ring A, B and C. 18
Functions of Flavonoids in Plants
They are the most important plant pigments for:
a) Flower colouration, producing yellow/blue pigmentation in petals for
pollination.
b) In higher plants , they are involved in filtration , symbiotic nitrogen
fixation and floral pigmentation.
c) They may also act as chemical messengers , physiological regulators, and
cell cycle inhibitors.
Name Formula Structure
Tangeretin 4', 5, 6, 7, 8-pentamethoxyflavone
Chrysin 5,7-dihydroxylflavone
Wogonin 5,7-dihydroxy-8-methoxyflavone
Biological activities of Flavonoids
Flavonoids have been reported to have a wide range of biological and
pharmacological activities in vitro studies e.g
Anti-allergic
Anti-inflammatory
Anti-oxidant
Anti-microbial