secondary metabolites
TRANSCRIPT
Secondary Metabolites
By Prabhu Thirusangu,Molecular Biomedicine Laboratory,Sahyadri Science CollegeKuvempu University
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• Primary metabolites: Molecules that are essential for growth and development of an organism.
Examples: 1.Carbohydrates 2.Proteins 3.Lipids
4.Nucleic acids 5.Hormones
• Secondary metabolites: molecules that are not essential for growth and development of an or-ganism.
Metabolites
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Secondary metabolites are derived from primary metabolites
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Why secondary metabolites?
• are biosynthetically derived from primary metabolites. They
are more limited in distribution being found usually in spe-
cific families. • Chemical warfare to protect plants from
the attacks by predators, pathogens, or competitors
• Attract pollinators or seed dispersal agents• Important for abiotic stresses • Medicine • Industrial additives
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• Possibly over 250,000 secondary metabolites in plants
• Classified based on common biosynthetic pathways where a chemical is derived.
• Four major classes: Alkaloids, glycosides, phenolics, terpenoids
Secondary metabolites
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Alkaloids
• Most are derived from a few common amino acids (i.e., tyrosine, tryptophan, or-nithine or argenine, and lysine)
• Compounds have a ring structure and a ni-trogen residue.
• Indole alkaloids is the largest group in this family, derived from tryptophan
• Widely used as medicine
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Terpenoids
• Terpenes are generally polymers of 5-carbon unit called isoprene
• Give scent, flavors, colors, medicine...
• Three plant hormones are derived from the terpenoid pathway.
ALKALOIDS
WHAT ARE ALKALOIDS?
• These are commonly applied to basic nitrogenous com-
pounds of plant origin that are physiologically active.
• Organic nitrogenous compounds with a limited distribu-
tion in native nature.
Characteristics:
• They are bitter in taste.
• Derived from amino acids.The amino acids that are most often serve
as alkaloidal precursors are: phenylalanine, tyrosine, tryptophan,
histidine, anthranilic acid, lysine and ornithine.
• Alkaloids form double salts with compounds of mercury, gold, plat-
inum and other heavy metals. These salts are obtained as precipitate
which are microcrystals.
• Insoluble or sparingly soluble in water, but the
salts formed on reaction with acids are usually
freely soluble.
• Most are crystalline solids although a few are
amorphous.
• Free alkaloids are usually soluble in polar solvents
like ether, chloroform
• Some alkaloids are liquid because of lacking of
oxygen in their molecules. (e.g coniine, nicotine,
spartenine)
Sources and Occurrence of Alkaloids
• Alkaloids can occur in plant kingdoms; among the an-
giosperms,
• Leguminosae,
• Papaveraceae,
• Ranunculaceae,
• Rubiaceae,
• Solanaceae,
• Berberidaceae are outstanding alkaloid-yielding plants.
Uses of Alkaloids in Plants:
• Poisonous agents which protect plants against insects and
herbivores
• End products of detoxification reactions representing a meta-
bolic locking-up of compounds otherwise harmful to the plants.
• For regulatory growth factors
• Reserve substance capable of supplying nitrogen or other ele-
ments necessary to the plant’s economy
Naming for alkaloids
• From the generic name or the genus of the
plant yielding them (e.g vinblastine and vin-
cristine. atropine)
• The specific name or species of the plant
yielding alkaloids ( e.g belladonnine)
• From their physiologic activity (e.g emetine,
morphine)
• From the discoverer (e.g pelletierine)
~ All names of alkaloids should end in “-ine”.
~ A prefix or suffix is added to the name of a principal
alkaloid from the same source. (quinine, quinidine,
hydroquinine)
Pharmacologic action of Alkaloids:
• Analgesic (morphine, codeine)• Narcotics (strychnine, brucine which are central stimu-
lant)• Anti malarial ( quinine)• Anti pyretic • Anti cancer (vincristine) • Mydriatics (atropine)• Anti inflammatory • Miotics (physostigmine, pilocarpine) • Ephedrine (rises in blood pressure, bronchodilator) • Reserpine (produce fall in excessive hypertension)
TYPES OF ALKALOIDS
True or hetero cyclic alkaloids
• Pyridine- Piperidine alkaloids• pyrrole & pyrrolidine alkaloids• Tropane alkaloids• Quinoline alkaloids• Isoquinoline alkaloids• Indole alkaloids• Imidazole alkaloids• Norlupinane alkaloids• Steroid alkaloids• Purine alkaloids
CHEMICAL CLASSIFICATION OF ALKALOIDS
TRUE ALKALOIDS
PYRROLE & PYRROLIDINE
DERIVATIVES e.g. Hygrine, Cocca
species
• Pyrrolizidine Derivatives
e.g. senecionine, seneciphylline
Piperidine & pyridine deriva-tivesAreca
ArecolineHydrobromide
Lobeline Nicotine
N
H
TROPANE DERIVATIVES
e.g. Atropine hyoscine
cocaineHyoscyamineScopolamine
Coca
QUINOLINE
DERIVATIVES
e.g. Quinine, quinidine,
cinchonine
CINCHONA BARK
Quinine
• Dia-stereo-isomer of quinidine
• It occurs as white, odourless, bulky crystals or as
a crystalline powder.
• It darkens when exposed to light and effloresces
in dry air.
• It is freely soluble in alcohol, ether and chloro-
form but slightly soluble in water.
Uses
• Antimalarial
• For treating of chloroquinine resistant falciparum
malaria combination with pyrimethamine and sulfa-
doxine or tetracycline or clindamycin.
• It has a skeletal muscle relaxant effect.
• It is widely used for the prevention and treatment of
nocturnal recumbency leg cramps.
ISOQUINOLINE DERIVATIVES
e.g. Morphine,
codeine,
berberine,
emetine
APORPHINE
(REDUCED
ISOQUINOLINE-NAPTHALENE)
DERIVATIVES
e.g. boldine
INDOLE DERIVATIVES
e.g. ergometrine,
ergotamine,
reserpine,
vincristine,
vinblastine
IMIDAZOLE DERIVATIVES
e.g. Pilocarpine,
isopilocarpine
NOR LUPINANE DERIVATIVES
e.g. Cytisine,
lupanine N
PURINE DERIVATIVES
e.g. Theophylline, caffeine,
theobromine
STEROIDAL DERIVATIVES
e.g. protoveratrine, solanidine
PSEUDO ALKALOIDS
DITERPENES e.g. Aconitine, aconine, hypoaconitine
PROTO OR NON HETERO CYCLIC ALKALOIDS
ALKYLAMINES
e.g. Ephedrine,pseudoephedrine, colchicine
• C17H19NO3
• a component of blackpepper (Piper ni-grum)
• has been used in various traditional medicine preparations
• an insecticide. has various effects on human drug metabolizing enzymes, and is mar-keted under the brand name, Bioper-ine,
PIPERINE
Quinine,1. molecular formula C20H24N2O2
2. is a white crystalline quinoline alkaloid.3. Quinine is extremely bitter, and also possesses
antipyretic, analgesic and anti-inflammatory properties.
4. has strong anti malarial properties,5. quinine in therapeutic doses can cause various
side-effects, e.g. nausea, vomiting and cinchon-ism, and in some patients pulmonary oedema.
6. It may also cause paralysis if accidentally in-jected into a nerve.
7. Non-medicinal uses of quinine include its uses as a flavouring agent in tonic water and bitter lemon.
VINCRISTINE
A CANCER KILLER
Vinca alkaloids The Vinca alkaloids are a subset of drugs that are de-
rived from the periwinkle plant, Catharanthus roseus.
N
N
OH
C2H5
H3COOC
N
N
R
OAc
OH COOCH3
H
H
MeO
Vinblastine R=-CH3
Vincristine R=-CHO
Serpentine
• Molecular Formula: C21H22N2O3
• Isolated from Rauwolfia serpentina • To treat High blood pressure • to treat insect stings and the bites of venomous reptiles
Terpenoids
Isoprene: Farnesol: Chlorophyll: β-Carotene
TERPENESThe chemist Leopold Ruzicka ( born 1887) showed that many compounds found in nature were formed from multiples of five carbons arranged in the same pattern as an isoprene molecule (obtained by pyrolysis of natural rubber).
He called these compounds “terpenes”.
C C
C
C C
.
isoprene
natural rubber
D
isoprene unit
head
tail
C C
C C
C
The Biological Isoprene Unit
• The isoprene units in terpenes do not come from isoprene.
• They come from isopentenyl pyrophosphate.• Isopentenyl pyrophosphate (5 carbons) comes
from acetate (2 carbons) via mevalonate
(6 carbons).
Terpenes
• Terpenes are natural products that are structurally related to isoprene.
H2C C
CH3
CH CH2or
Isoprene(2-methyl-1,3-butadiene)
The Biological Isoprene Unit
CH3COH
O
3 HOCCH2CCH2CH2OH
CH3
OH
O
Mevalonic acid
H2C CCH2CH2OPOPOH
CH3 O O
Isopentenyl pyrophosphate
Isopentenyl Pyrophosphate
H2C CCH2CH2OPOPOH
CH3 O O
Isopentenyl pyrophosphate
or
OPP
Isopentenyl and Dimethylallyl Pyrophosphate
Isopentenyl pyrophosphate is interconvertible with2-methylallyl pyrophosphate.
OPP
OPP
• Dimethylallyl pyrophosphate has a leaving group (pyrophosphate) at an allylic carbon; it is reactive toward nucleophilic substitution at this position.
Isopentenyl pyrophosphate Dimethylallyl pyrophosphate
Carbon-Carbon Bond Formation
• The key process involves the double bond of isopentenyl pyrophosphate acting as a nucleophile toward the allylic carbon of dimethylallyl py-rophosphate.
+OPP
OPP
After C—C Bond Formation...
+
OPP
• The carbocation can lose a proton to give a double bond.
After C—C Bond Formation...
+
OPP
OPP
• The carbocation can lose a pro-ton to give a double bond.
H–+
After C—C Bond Formation... OPP
• This compound is called geranyl pyrophosphate. It can undergo hydrolysis of its pyrophosphate to give geraniol (rose oil).
OPP OH
Geraniol
H2O
After C—C Bond Formation...
From 10 Carbons to 15 +
OPP
OPP
Geranyl pyrophosphate
+OPP
From 10 Carbons to 15
+OPP
H–+
OPP
From 10 Carbons to 15 OPP
• This compound is called farnesyl pyrophosphate.• Hydrolysis of the pyrophosphate ester gives the
alcohol farnesol.
Cyclization
• Rings form by intramolecular carbon-carbon bond formation.
OPP
OPP
+
E double bond
Z double bond
CLASSIFICATION OF TERPENES
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TYPE OF NUMBER OF ISOPRENE TERPENE CARBON ATOMS UNITS
hemiterpeneterpenesesquiterpenediterpene
triterpene
tetraterpene
C5
C10
C15
C20
C30
C40
one two three four
six
eight
hemi = half di = two Sesqui = one and a half tri = three
tetra = four
NOTE:
• Hemiterpenes consist of a single isoprene unit. Isoprene itself is considered the only hemiterpene, but oxygen-containing derivatives such as prenol and isovaleric acid are hemiterpenoids.
• Monoterpenes consist of two isoprene units and have the molecular formula C10H16. Examples of monoterpenes are: geraniol,limonene and terpineol.
• Sesquiterpenes consist of three isoprene units and have the molecular formula C15H24. Examples of sesquiterpenes are: humulene,farnesenes, farnesol.
• Diterpenes are composed of four isoprene units and have the molecular for-mula C20H32. They derive from geranylgeranyl pyrophosphate. Examples of diterpenes are cafestol, kahweol, cembrene and taxadiene (precursor of taxol).
CLASSIFICATION OF TERPENES
• Sesterterpenes, terpenes having 25 carbons and five isoprene units, are rare relative to the other sizes, example: geranylfarnesol.
• Triterpenes consist of six isoprene units and have the molecular for-mula C30H48. The linear triterpene squalene, the major constituent of shark liver oil, is derived from the reductive coupling of two mole-cules of farnesyl pyrophosphate. Squalene is then processed biosynthetically to generate either lanosterol or cycloartenol , the structural precursors to all the steroids.
• Sesquarterpenes are composed of seven isoprene units and have the molecular formula C35H56. Sesquarterpenes are typically microbial in their origin. Examples of sesquarterpenes are ferrugicadiol and tetraprenylcurcumene.
CLASSIFICATION OF TERPENES
• Tetraterpenes contain eight isoprene units and have the molecular formula C40H64. Biologically important tetraterpenes include the acyclic lycopene, the monocyclic gamma-carotene, and the bicyclic alpha- and beta-carotenes.
• Polyterpenes consist of long chains of many isoprene units,eg, Natu-ral
rubber .
• Norisoprenoids,eg: C13-norisoprenoids 3-oxo-α-ionol present in
Muscat of Alexandria leaves and 7,8-dihydroiononederivatives, such as megastigmane-3,9-diol and 3-oxo-7,8-dihydro-α-ionol found in
Shiraz leaves (both grapes in the species Vitis vinifera)
CLASSIFICATION OF TERPENES
TERPENES
1. The number of C atoms is a multiple of 5, C5
C10 C15 C20 C25 C30 C35 C40
2. Each group of 5 C is an isoprene subunit
3. They can be saturated or unsaturated
4. Many contain O atoms as well.
5. What they all have in common is 1 & 2 above.
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JOINING ISOPRENE UNITS
The terms head-to-tail andtail-to-tail are often used todescribe how the isoprene
units are joined.
C C
C
C C
.
an extrabond
Head-to-Tail
Head-to-Tail
Tail-to-Tail
a-Phellandrene
(eucalyptus)Menthol
(peppermint)Citral
(lemon grass)
O
H
OH
Representative Monoterpenes
Representative Monoterpenes a-Phellandrene
(eucalyptus)Menthol
(peppermint)Citral
(lemon grass)
O
H
OH
a-Phellandrene
(eucalyptus)Menthol
(peppermint)Citral
(lemon grass)
Representative Monoterpenes
Representative Sesquiterpenes
a-Selinene(celery)
H
a-Selinene(celery)
H
Representative Sesquiterpenes
Vitamin A
OH
Representative Diterpenes
Vitamin A
OH
Representative Diterpenes
Vitamin A
Representative Diterpenes
Squalene(shark liver oil)
tail-to-tail linkage of isoprene units
Representative Triterpenes
Farnesol
Used as
1. Perfumes2. Pesticides3. Pheromones4. Anti- tumour agent5. Antibacterial drug
Structure of chlorophyll
Chlorophyll a & b• Chl a has a methyl
group
• Chl b has a car-bonyl group
Porphyrin ring delocalized e-
Phytol tail
Structure of chlorophyll a and b
β-carotene-TETRATERPENE
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β-carotenecarrots
tail-to-tailhead-to-tail
head-to-tail
β-carotene – a linear terpene
8 isoprene units
40 carbon atoms
CH2
CH2
CH2C
CC
CH3CH3
CHCH
CCH
CHCH
CCH
CHCH
CHC
CHCH
CHC
CHCH
CC
CH2
CH2CH2
CCH3
CH3 CH3CH3 CH3
CH3CH3
CH3
-carotene
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• Taxol is a terpenoid • "the best anti-cancer agent” by National
Cancer Institute • Has remarkable activity against advanced
ovarian and breast cancer, and has been approved for clinical use.
Taxol
Taxus brevifolia Nutt.
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• Camptothecin is an indole alkaloid, derived from tryptophan.
• Has anticancer and antiviral activity • Two CPT analogues have been used in can-
cer chemotherapy, topotecan and irinote-can.
Phenolics
• Derived from aromatic amino acids, such as phenylalanine, tyrosin, and trytophan.
• All contain structures derived from phenol• Some examples:
Coumarins: antimicrobial agents, feeding deterrents, and germination inhibitors.
Lignin: abundant in secondary cell wall, rigid and resistant to extraction or many
degradation reagents Anthocyanins
FlavonesFlavnols
Phenols are present in every plant they attract pollinators to the plant and even
impact how these plants act with one an-other.
.
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Glycosides
• Compounds that contain a carbonhydrate and a noncarbohydrate
• Glycosides are present in vacuoles in inactive form
• Glucosinolates: found primarily in the mustard family to give the pungent taste
There are four type of linkages present between glycone and aglycone:
C-linkage/glycosidic bond, O-linkage/glycosidic bondN-linkage/glycosidic bondS-linkage/glycosidic bond
• .
Cyanogenic glycosidesAll of these plants have these glycosides stored in the vacuole, but, if the plant is attacked, they are released and become activated by enzymes in the cytoplasm. These remove the sugar part of the molecule and release toxic hydrogen cyanide.An example of these is amygdalin from bitter almondsCyanogenic glycosides can also be found in the fruit seeds (and wilting leaves) of many members of the rose family (including cherries, apples, plums, bitter almonds, peaches, apricots,raspberries, and crabapples
SourcesPlant resins[
A liquid compounds found inside plants or exuded by plants, But not saps, latex, or mucilage,The resin produced by most plants is a viscous liquid, composed mainly of volatile fluid terpenes resins do not serve a nutritive function. The toxic resinous compounds may confound a wide range of herbivores, insects, and pathogens; while the volatile phenolic compounds may attract benefactors such as parasitoids or predators of the herbivores that attack the plants
Latex latex as found in nature is a milky fluid found in 10% of all flowering plants (angiosperms). It is a complex emulsion consisting of proteins, alkaloids, starches, sugars, oils, tannins, resins, and gums that coagulate on exposure to air. It is usually exuded after tissue injury. In most plants, latex is white, but some have yellow, orange, or scarlet latex. It serves mainly as defense against herbivorous insects.
Natural rubber is the most important product obtained from latexThis latex is used to make many other products as well, including mattresses, gloves, swim caps, catheters and balloonsIn chewing gum, and glues
SourcesPlant sterol;The richest naturally occurring sources of phytosterols are vegetable oils and products made from them. They can be present in the free form and as esters of fatty acid/cinnamic acid or as glycosides, Phytosterols, which encompass plant sterols and stanols, are steroid compounds similar to cholesterol which occur in plants and vary only in carbon side chains and/or presence or absence of a double bond. Stanols are saturated sterols, having no double bonds in the sterol ring structure.
SourcesSapogeninssapogenins are the aglycones, or non-saccharide, portions of the family of nat-ural products known as saponins. Sa-pogenins containsteroid or other triterpene frameworks as their key organic feature. For example, steroidal sapogenins like tiggenin, neogitogenin, and tokorogenin have been isolated from the tubers of Chlorophytum arundi-nacelum. Some steroidal sapogenins can serve as a practical starting point for the semisynthesis of particular steroid hormones.
Essential OilAn essential oil is a con-centrated hydrophobic liquid containing volatile aroma compounds from plants. Essential oils are also known as volatile oils, ethereal oils, aetherolea, They are used in perfumes, cosmetics, soaps and other products, for flavoring food and drink, and for adding scents to incense and household cleaning products
Oil Tonnes
Sweet orange 12,000
Mentha arvensis 4,800
Peppermint 3,200
Cedarwood 2,600
Lemon 2,300
Eucalyptus globulus 2,070
Litsea cubeba 2,000
Clove 2,000
Spearmint 1,300
PhenylpropanoidsThe phenylpropanoids are a diverse family of organic compounds that are synthesized by plants from the amino acid phenylalanine
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.
Plant-derived Insecticides
Outline: Plant-Derived Insecticides
Important insecticides from plants -rotenoids - New World and Asia -pyrethrins - Near Eastern cen-ter
-tobacco - New World Ryania speciosa, Flacourtiaceae
Antifeedants -neem, Azadirichta indica, Meli-aceae
Introduction
• Many insecticidal compounds are known from plants. Most plants make defensive compounds called allomones. Only a few are important commercially.
• Plant-derived insecticides have largely been replaced by synthetic materials, but there are some advantages to the naturally occurring materials. For ex-ample, these substances are biodegradable.
• Selectivity is needed. Compounds that are toxic to insects, but not toxic to mammals, are preferable, of course.
Rotenoids
• A series of compounds found in mem-bers of the genera Derris, Lonchocar-pus, Tephrosia are known as rotenones.
• Commercially, rotenoids are isolated mostly from the roots of Derris elliptica in Indonesia and from Lonchocarpus
• These compounds are isolated by grind-ing the plant and extracting with sol-vents such as hexane or petroleum ether or chloroform.
• The compounds are oil soluble or lipids. They make up 1-20% of the dry weight of the roots.
Derris elliptica, Fabaceae
Pacific Island Ecosystems at Risk (PIER)Photo by Agnes Rinehart
Rabo molle, Lon-chocarpus muehlen-bergianus, Fabaceae
Libro del Arbol, Celulosa Argentina, Vol. 2, 1975
False indigo bush, Amorpha fruticosa, Fabaceae
Pyrethrins
• Another major series of compounds, the pyrethrins, come from species of the genus Chrysanthemum (some people put these species in Pyrethrum) (Aster-aceae or Compositae).
• These were used as far back as the 1st century B.C. by the Chinese. Insecticidal plants mostly are grown in countries with inexpensive labor and high eleva-tions such as Kenya and New Guinea.
Pyrethrum, Chrysanthemum cinerariifolium, Asteraceae
Courtesy Dr. Saifu Dossaji
Harvesting pyrethrum flowers in Kenya
Courtesy Dr. Saifu Dossaji
• Ryania speciosa (Flacourtiaceae) is also used occasionally and an insec-ticide.
• A mixture of diterpene, alkaloids is isolated and used for specialty in-secticide uses.
• Because the extract is expensive, it is not commonly used.
Other plant-derived insecti-cides
Ryania speciosa, flower and fruit, Flacour-tiaceae
Tobacco, Nicotiana tabacum, Solanaceae
• Tobacco (which contains nicotine) is another major source of insec-ticides. Tobacco wastes are often extracted and used as a source of nicotine. Nicotine especially effective against aphids.
Tobacco, Nicotiana tabacum, Solanaceae,
Calabar bean
• Calabar bean (Physostigma venenosa, Fabaceae) is (or has been) a trial-by-ordeal drug in the Calabar coast of Nigeria. The ac-tive component is physostigmine, an acetyl choline esterase inhibitor.
• The structure of several commercial carbamate insecticides is patterned after the structure of the plant alkaloid.
Calabar bean, Physostigma venenosum, Fabaceae
R. Bentley and H. Trimen, Medicinal Plants, London, Churchill, 1880
Antifeedants
• Antifeedants are compounds that prevent insect feeding. Although many are toxic, the insects usually don’t consume enough to be poisoned.
• Only one of these, neem, Azadirachta indica, Meliaceae, is commercially available. The active compound, azadirachtin, is a structurally modified triterpene.
Neem, Azadirachta in-dica, Meliaceae
Courtesy Dr. Ramesh PandeyWilliam M. Ciesla, Forest Health Management International, United
States
108
Natural ColorsAnd
Flavors
Better & Safer Alter-natives
109
Natural Colors saffron Anthrocyanin Carotenoids Carotene Chlorophyll Curcumin Iron oxides Riboflavin Titanium dioxides
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Carotenoids Yellow & Red colors.
Sources- Sweet potatoes, spinach and tomatoes. Antioxidant - Cancer research.
111
Carotene
Yellow to Orange colors.
Sources: Carrots, yellow or orange fruits.
Rich in Vitamin A.
Lycopenesaffron
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Chlorophyll
Green coloring agent.
Occurs naturally in all plants
113
Curcumin• Extracted from turmeric.• Coloring and medicinal uses• Wound healing• Antiulcer• Anti inflammatory• Antimicrobial & antiviral • Hepatoprotective• Antioxidant• No toxicity.
114
Riboflavin (Vitamin B2)
Yellow to Orange colors.
Sources- Leafy vegetables, Eggs, Milk & Wheat.
Safe & Beneficial for health.
115
Sweet Orange Oil
• Sweet orange fruit peel
Stress reducing agent
Aroma therapy: Peace of mind
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Flavor
Cocoa seedsVennilaStrawberryCinnamonCardamomClovesPepperareca