Pharmacognosy
Final year B.Pharm
University of Mumbai
Phenylpropanoids are a diverse group of natural products composed of thousands of different compounds, synthesized from the primary metabolites, phenylalanine or tyrosine amino acids, through a series of enzymatic reactions. ... 4-Coumaryl Co-A serves as the common precursor to flavonoid and phenolic acids biosynthesis.
3. Introduction
Secondary metabolites are extensively distributed in the plant kingdom. They play an
essential role in growth, development and reproduction of plants. Moreover, they are
known to impart protection to plants against their competitors via allelopathy.
Secondary metabolites also protect the plants by herbivores, insects, microorganisms,
exposure to UV radiation, drought, and heat stress
Phenolics are major group of secondary metabolites,which can be sorted into following
subgroups, i.e., the phenolic acids, flavonoids, coumarins, curcuminoids, stilbenes ,
quinones, lignans, tannins, phenolic terpenoids and phenolic alkaloids
Further, phenolic acids are categorized into two main groups:
(i). Hydroxybenzoic acids, comprising of a backbone of seven carbon atoms (C6-C1),
includes p-hydroxybenzoic acid, protocatechuic acid, gallic acid, vanillic acid and
syringic acid;
(ii).hydroxycinnamic acids (HCiA), containing nine carbon atoms (C6-C3)
phenylpropanoid backbone, includes p-coumaric acid (p-CoA), caffeic acid (CA), ferulic
acid (FA) and sinapic acid (SA)
4. Both plant-based, as well as synthetic phenylpropanoids (PPs) and their derivatives
have gained attention due to their low toxicity and wide array of bioactive
properties, involved in human disease management.
In this slide we are going to learn about flavonoids , their classification , chemical
tests, occurrence and their biopotential as exemplified orange peel , soyabean,
buckwheat and psoralea . Also
Moreover discussed about monomeric , dimeric and related polypropanoid
derivatives with example of lignans., Podophyllum
5. Phenylpropanoids
The phenylpropanoids are a diverse family of organic compounds that are synthesized
by plants from the amino acids phenylalanine and tyrosine.
Their name is derived from the six-carbon, aromatic phenyl group and the three-carbon
propene tail of coumaric acid, which is the central intermediate in phenylpropanoid
biosynthesis. From 4-coumaroyl-CoA emanates the biosynthesis of myriad natural
products including lignols (precursors to lignin and lignocellulose), flavonoids,
isoflavonoids, coumarins, aurones, stilbenes, catechin, and phenylpropanoids.The
coumaroyl component is produced from cinnamic acid.
Phenylpropanoids are found throughout the plant kingdom, where they serve as
essential components of a number of structural polymers, provide protection from
ultraviolet light, defend against herbivores and pathogens, and mediate plant-pollinator
interactions as floral pigments and scent compounds.
Concentrations of phenylpropanoids within plants are also altered by changes in
resource availability.
6. Phenylpropanoids and other phenolics are part of the chemical composition of
sporopollenin.
This substance found in pollen is not exactly known, due to its unusual chemical
stability and resistance to degradation by enzymes and strong chemical reagents.
Analyses have revealed a mixture of biopolymers, containing mainly long chain
fatty acids, phenylpropanoids, phenolics and traces of carotenoids.
Tracer experiments have shown that phenylalanine is a major precursor, but other
carbon sources also contribute. It is likely that sporopollenin derives from several
precursors that are chemically cross-linked to form a rigid structure
7. Sporopollenin
Phenylpropanoids and other phenolics are part of the chemical composition of
sporopollenin. It is related to cutin and suberin.
Sporopollenin is found in plants pollen grains in its outer layer called exine.
Sporopollenin is one of the most resistant organic material known. It can
withstand high temperatures and strong acids and alkali. No enzyme that
degrades sporopollenin is so far known.
This ill-defined substance found in pollen is unusually resistant to degradation.
Analyses have revealed a mixture of biopolymers, containing mainly hydroxylated
fatty acids, phenylpropanoids, phenolics and traces of carotenoids.
Tracer experiments have shown that phenylalanine is a major precursor, but other
carbon sources also contribute.
It is likely that sporopollenin is derived from several precursors that are chemically
cross-linked to form a rigid structure.
https://youtu.be/d4vcdNBzFT0
8. Phenylpropanoids : Biosynthesis
The phenylpropanoid metabolism is unique to plants.
Many intermediates and end products of the phenylpropanoid pathway play important
roles in plants as phytoalexins, antioxidants, antiherbivory compounds, UV protectants,
pigments, and aroma compounds. Phenylpropanoids polymerize to form lignins, which
are essential components of the cell wall stability.
Phenylpropanoid biosynthesis is one of the best-studied pathways in plants. The
enzymes of the phenylpropanoid pathway are organized in multi-enzyme complexes
and there is evidence for the coordinated expression of genes and enzymes. Genes
encoding enzymes of this pathway are developmentally and tissue-specifically regulated
and may be induced by environmental stresses such as nutrient deficiency, exposure to
cold, UV light, and pathogen attack.
9. Overview of the
phenylpropanoid
biosynthetic
pathway. The
phenylpropanoid
biosynthesis starts
from phenylalanine
and tyrosine
leading to various
classes of chemicals
including
hydroxycinnamic
acids, monolignols,
stilbenoids,
flavonoids, and
coumarins.
10. Phenylalanine and tyrosine are deaminated by phenylalanine ammonia lyase (PAL)
or tyrosine ammonia lyase (TAL) to cinnamic acids. The cinnamic acids (C6-C3) are
the precursors to the phenyl propanoids, coumarins, styrenes, benzoic acids,
phenols, and flavonoids. A multi-enzyme complex enables coordinated action of
PAL and cinnamate-4-hydroxylase (C4H) which control the flux of intermediates in
phenylpropanoid biosynthesis.
11. Coumarins and flavonoids
Hydroxylation of cinnamic acid in the 4-position by trans-cinnamate 4-
monooxygenase leads to p-coumaric acid, which can be further modified into
hydroxylated derivatives such as umbelliferone. Another use of p-coumaric acid via
its thioester with coenzyme A, i.e. 4-coumaroyl-CoA, is the production of chalcones.
This is achieved with the addition of 3 malonyl-CoA molecules and their cyclization
into a second phenyl group. Chalcones are the precursors of all flavonoids, a
diverse class of phytochemicals.
13. Flavonoids
The flavonoids are polyphenolic compounds possessing 15 carbon atoms; two
benzene rings joined by a linear three carbon chain having the carbon skeleton C6
- C3 - C6 and they are the plant pigments and they are having polar nature and is
soluble in methanol and water.
Flavonoids constitute one of the most characteristic classes of compounds in
higher plants. Many flavonoids are easily recognized as flower pigments in most
angiosperm families (flowering plants).
However, their occurrence is not restricted to flowers but include all parts of the
plant.
They are secondary metabolite and effective in CNS disorders
14. They are responsible for the color of flowers, fruits and sometimes leaves.
Widely distributed in different amounts, according to the plant species, organ, developmental
stage and growth conditions.
The Flavonoids have aroused considerable interest recently because of their potential beneficial
effects on human health as well as their role in plant metabolism.
They ensure tissue protection against the damaging effects of UV radiation.
They have been reported to have antiviral, antitumor, antiallergic, anti-platelet, anti-
inflammatory and antioxidant activities.
15. Dietary sources of flavonoids
Flavonoids (specifically flavanoids such as the catechins) are "the most common group
of polyphenolic compounds in the human diet and are found ubiquitously 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.
Foods with a high flavonoid content include parsley, onions , blueberries and other
berries , black tea ,green tea and oolong tea , bananas, all citrus fruits, Ginkgo biloba,
red wine, sea-buckthorns, buckwheat , and dark chocolate with a cocoa content of 70%
or greater.
16. Parsley is a source of flavones Blueberries are a source of dietary
anthocyanidins
A variety of flavonoids are found in citrus fruits, including
grapefruit
17. Structure of flavonoids
Their basic structure is a skeleton of
diphenylpropane, namely, two benzene rings (ring
A and B, see figure) linked by a three carbon chain
that forms a closed pyran ring (heterocyclic ring
containing oxygen , the C ring) with benzenic A
ring.
Therefore, their structure is also referred to as C6-C3-C6. In most cases, B ring
is attached to position 2 of C ring, but it can also bind in position 3 or 4; this,
together with the structural features of the ring B and the patterns of
glycosylation and hydroxylation of the three rings, makes the flavonoids one
of the larger and more diversified groups of phytochemicals
18. Chemical structure
Many authors apply the term flavonoids to flavon-, flavanon-, and flavonol-
derivatives.
They occur in free state and as glycosides, most are O-glycosides.
But a considerable number of flavonoid C-glycosides are known.
In all the classes of flavonoids mentioned so far, biosynthesis frequently places at
least 3 phenolic OH-groups in the 5-, 7-, and 4´-positions of the aglycone.
flavanone
19. Classification
They fall into many classes depending on the degree of oxidation of the central
pyran ring:
1- Flavanones (4-Oxo-flavane) such as naringenin.
2- Flavones (4-Oxo-flav-2-ene) such as apigenin.
3- Flavonols (3-Hydroxy-4-Oxo-flav-2-ene) such as quercetin.
4- Flavanols (3-Hydroxyflavane, Catechine) such as (+)-catechine.
5- Flavandiols (3,4-Hydroxyflavane) Leukoanthocyanidine).
6- Flavylium-salts (Anthocyanidine) such as cyanidine.
23. Chemical tests
Shinoda test : drug solution + Mg turning + conc. HCL drop wise , pink scarlet ,
crimson red or occasionally green to blue appears in few minutes.
Alkaline reagent test : drug solution + NaOH , intense yellow color is formed which
turns to colorless on addition of few drops of dil. Acid
Zinc HCL test : drug solution + zinc dust + Conc. HCL , red color after few minutes.
Ammonia test : Filter paper dipped in alcoholic solution, when exposed to ammonia
vapor yellow spot
Vanillin HCl test :Vanillin HCl added to alcoholic solution of drug pink color
flavonoids
https://youtu.be/CC3t67e2GsU
24. Flavonoids
Longevity
Anthocyanins, resveratrol ,
quercetin etc.
Weight management
Quercetin , isoflavone,
catechin etc.
Cardiovascular diseses
Quercetin , kaemferol and
Naringenin etc.
Diabetes
Quercetin,puerarin, hesperidin
etc.
Cancer prevention
Kaempferol ,
anthocyanidin,quercetin etc.
Signal molecules
Anthocyanins , quercetin,
anthocyanidins etc
Phytoalexins
Kampferol,luteolin,quercetin ,
etc
Detoxifying agent
Quercetin, kampferol ,catechol
etc
Stimulant for germination
Anthocyanins, apigenin,quercetin
etc
Pollinator attractions
Anthocyanins, hespiridin.,
quercetin etc.
Plant health benefits
Human health benefits
25. Orange peel (Hesperidin)
Synonyms - Orange cortex,
Bigarade orange, Seville orange,
china Orange, Bitter orange peel
The orange peel is the fresh or
dried outer part of the pericarp of
Citrus aurantium Linn,
belonging to family Rutaceae.
It is mainly cultivated in India,
China, Spain, Madeira, Sicily,
Malla, and Morocco.
26. Collection & Preparation
Orange Peel is cultivated in Mediterranean countries and England.
The peel should be removed with as little of white ‘ zest’ as possible.
Hand cut English dried peel is most esteemed.
The peel may be removed in four quarters or in spiral band.
It is also found in thin strips similar to those found in marmalade cut by machines.
They so called maltese is of this type which is known as ‘gelatin cut’.
27. Chemical constituents
Bitter orange peel contains of 1 to 2.5% volatile oil. The principle component of
volatile oil is 90% limonene and small quantities of aldehydes citral , citronellal,
bitter amorphous glycoside like aurantiamarin and it’s acid; hesperidin,
isohesperidin , vitamin C, and Pectin.
Limanene (90%)
Citral (4%)
Vitamin C
Pectin
Hesperidine ( Flavonoid )
Aurantimarin and Aurantimaric acid ( Both are glycoside and responsible for
bitter)
28. Chemical test
Shinoda Test :-
A small quantity of test residue is dissolved in 5 ml of ethanol (95% v/v) and
treated with few drop of conc. Hcl and 0.5 g of magnesium metal, pink or red colour is
developed.
Hespiridin
29. Uses
Orange peel, which is the primary waste fraction in the production of orange juice,
contains flavonoids associated with antioxidant activity
The glycosides hesperidin and naringin are mainly responsible for the purported
antioxidant activity of citrus peel extracts .
Coniferin and phlorin are additional phenols in orange peels that have been found
to aid in radical scavenging when administered in the form of orange peel
molasses .
prevention and management of capillary fragility so used in hypertension , CVS
disorders
30. Soyabean ( Isoflavones )
Source : dried seeds of Glycine max
Family : Leguminose
Constituents : Isoflavones
Isoflavones are a class of phytoestrogens — plant-derived
compounds with estrogenic activity. Soybeans and soy
products are the richest sources of isoflavones in the human
diet.
Use : Soy flavonoids (isoflavones) can also reduce blood
cholesterol and can help to prevent osteoporis .
Soy flavonoids are also used to ease menopausal symptoms.
CVS , Mental and Women’s health , cancer prevention
31.
32. Buckwheat ( Rutin )
Source – powder of dried food grains of Fagopyrum
esculentum
Family – Polygonaceae
Geographical source – food crop in United states,
Russia and Japan
Constituents – 12% protein , 2 % fat and mainly Rutin
Rutin is microcrystalline greenish yellow tasteless
powder, soluble in methanol-isopropyl alcohol-
pyridine-alkali hydroxides
Use: capillary bleeding along with increased capillary
fragility so used in retinal haemorrhage
33. Rutin isolation , identification and analysis
It is a bioflavonoid
Pure rutin is yellow or yellow green color, needle shaped crystal
Take 20 gm powder soxhlet with 250 ml 80% ethanol.
Filter it, mix it with 25 ml water &
extracted with pet. Ether & CHCl3
Take Aq. Layer keep in cold for 72 hrs.
Yellow ppts. Seperated .
washed with CHCl3: ethyl acetate: ethanol (50:25:25)
34. Ppts dissolved in hot methanol & filter it
The filtrate is evaporated to dryness
Get yellow powder (rutin)
Identification Test:
1) With FeCl3 ---- give dark green color
2) With lead acetate ---- orange yellow ppts
3) With ammonium molybdate & antimony trichloride ---- orange
yellow ppts
Rutin
35. Analysis
1) TLC & Paper Chromatography:
Precoated aluminium sheet with silica gel G
Mobile Phase: Ethyl acetate: butanone: formic Acid:water(50:30:10:10)
Ethyl acetate: formic Acid: Acetic Acid :water(100:10:11:27)
In Paper C.: Stationary phase: filter paper (W.-1)
Mobile Phase: acetic acid: water (15:85)
isopropyl alcohol: water (60:40)
2) Spectrophotometric:
Dissolved in methanol & detect in UV.
36. Coumarins
Coumarin is the parent organic compound of a class of naturally occurring
phytochemicals found in many plant species. This oxygen heterocycle is best known for
its fragrance, described as a vanilla like odor or the aroma of freshly mowed hay.
Identified in the 1820s, coumarin has been synthesized in the laboratory since 1868 and
used to make perfumes and flavorings. It is also used to prepare other chemicals in
particular anticoagulants and rodent poison.
Coumarin is found in a variety of plants such as Tonka bean, lavender, sweet clover
grass, and licorice, but also occurs in food plants such as strawberries, apricots, cherries,
and cinnamon. It is thought to work by serving as a pesticide for the plants that
produce it.
Chemically, coumarin can occur either free or combined with the sugar glucose to
produce a coumarin glycoside. Medically, coumarin glycosides have been shown to
have blood thinning, antifungicidal , and anti-tumor activities. Dicumarol, a coumarin
glycoside better known as warfarin, is the most commonly used oral anticoagulant
medication.
39. Chemical Test:
psoralen, dissolved in alcohol + NaOH UV light observation yellow
fluorescence
Psoralen, dissolved in small amount of alcohol, 3 times propylene glycol, 5 times
acetic acid, 40 times water UV light observation blue fluorescence
Uses:
Aphrodisiac, antibacterial, astringent, cytotoxic, diaphoretic, diuretic, stimulant,
stomachic , tonic, lower back pain, skin disease, bed wetting, leprosy, hair loss
Psoralen Psoralidin
40. e.g. Lignans - Podophylllum
Monomeric , dimeric phenylpropanoid
42. Lignan : Dimeric derivatives
Dimeric compounds formed essentially by the union of the two molecules of a
phenylpropene derivative.
Not synthesized by lignin biosynthetic pathway.
Unlike lignin, optically active and probably arise by stereospecific, reductive coupling
between the middle carbons of the side chain of monomer.
Some 300 lignans have been isolated and categorized into a number of groups
according to structural features.
Important pharmaceutical examples are the lignans of Podophyllum spp. which
appear to be formed from two molecule of coniferyl alcohol or the corresponding acid
with subsequent modification; apparently, a sinapic acid derivative, as might be
expected by the inspection of the podophyllotoxin molecule, is not involved.
43. Continued..
Lignans can be found in more than 60 families of vascular plants and have been isolated
from different plant parts, exudates and resins.
Biological activity of Lignans - are Antiviral ,Anticancer ,Cancer prevention, Anti-
inflammatory, antimicrobial ,antioxidant , immunosuppressive, Hepatoprotective,
Osteoporosis prevention.
Based on their carbon skeleton, cyclization pattern, and the way in which oxygen is
incorporated in the molecule skeleton, they can be divided into 8 subgroups:
Main subclasses of Lignans- 1.Furofuran, 2.Furan, 3.Dibenzylbutane,
4.Dibenzylbutyrolactol, 5.Dibenzylbutyrolactones, 6.Aryltetralin, 7.Arylnaphtalene,
8.Dibenzocyclooctadienes.
among these subgroups, the furan, dibenzylbutane and dibenzocyclooctadiene lignans
can be further classified in “lignans with C9 (9´)-oxygen” and “lignans without C9 (9´)-
oxygen”
44. Lignin
It is an important polymeric substance, (C6-C3)n, laid down in a matrix of cellulose
microfibrils to strength certain cell wall.
It is an essential component of most woody tissues and involves vessels, tracheids,
fibres and sclereids.
Lignins from different biological sources vary in composition, depending on the
particular monomeric units in which they are composed.
Variations in lignin constitutes also arise as a result of random condensations of the
appropriate alcohols with mesomeric free radicals formed from them by the action
of a laccase type (oxidase) enzyme.
As there is no template for this non-enzymatic condensation the lignin molecules
formed vary in structure and so it is not possible to isolate lignin as a compound of
defined composition.
45. Continued ..
In the wall, it appears to occur chemically combined with hemicellulose and built
up in greatest concentration in the middle lamellae and in the primary walls.
Lignified cell walls after treatment with Schultze’s macerating fluid (HNO3+
Potassium chlorate) will show cellulose reactions.
Acid Aniline sulphate bright yellow
Phloroglucinol + conc. HCl pink/red
Chlor-zinc-iodine yellow
46. Lignin vs Lignan - What's the difference?
As nouns the difference between lignin and lignan is that lignin is (organic
compound) a complex non-carbohydrate aromatic polymer present in all wood
while lignan is (organic chemistry) any of a class of phenylpropanoid
(propylbenzene) type of molecules found in essentially all plants, generally dimeric
or higher order, and produced by secondary metabolic pathways branching off of
aromatic amino acid biosynthesis, in some cases having associated antioxidant or
estrogenic (phytoestrogenic) activities; having in common with lignin the
phenylpropanoid monomers, where lignin is a random oxidative polymerization of
the same.
47. Podophyllum : Lignan
Synonyms: May apple, Wild
mandrake
Source: dried roots and rhizomes of
American: Podophyllum peltatum
& Indian: Podophyllum
hexandrum (P.emodi)
Family: Podophyllaceae
(Berberidaceae)
GS: America (US-Virginia, Kentucky,
North carolina, Tennessee, Indiana
)& Canada
Indian: Tibet, China, Afghanistan,
Himalayas
48.
49. The rhizomes and roots are obtained from wild grown plants growing at an
altitude of 3000 to 4000 m.
Underground rhizomes remain dormant in winter and produce aerial shoots in
April to May.
Shoots flower during summer and die in November
Rhizomes and roots are dug up in spring or autumn, washed, cleaned and dried in
the sun
The drug collected in the month of may has higher resin content than the collected
in November.
Actually the roots contain more resin than rhizomes and hence roots are preferred.
50. Constituents :
P. peltatum
2-8% resinous material as podophyllin, Lignan derivatives: podophyllotoxin, alpha
& beta peltatin, (Lignan: in form of glycoside), Desmethyl podophyllotoxin,
desoxypodophyllotoxin, podophyllotoxone,
Flavonoid: quercetin, kaempferol, essential oil, Starch
P. hexandrum
7-15% Resin as Podophyllin
40% podophyllotoxin
53. Chemical Test
Alcoholic ext. + strong copper acetate- brown ppt with Indian podophyllum &
green color without ppt with American podophyllum
USES:
Cyto-toxic, venereal disease, Warts,
Podophyllotoxin is semisynthetically converted to etoposide potent anticancer
agent for lung & testicular.
Its GIT irritant, drastic purgative in moderate uses
54. Podophyllum Species
American Podophyllum
Vascular bundles are not so
elongated radially.
The CaOx crystals are fewer and
smaller (30-60-100 Micro meter)
Less resin 2-8 %
Contains alpha & beta peltatin
Podophyllotoxin is less
Indian Podophyllum
Vascular bundles are more elongated
radially.
The CaOx crystals are fewer and
smaller (20-30-60 Micro meter)
More resin up to 7-15%
No constituents
Podophyllotoxin is more