Biosynthesis of Plant Derived Flavour

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Biosynthesis ofPlant-derived flavor

compounds

By Dudsadee Uttapap


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References

. Flavor Chemistry and Technology, H.B. Heath, G. Reineccius, .

. Flavor Chemistry, D.B. Min, http://class.fst.ohio-state.edu/fst /default.htm

3. Biosynthesis of plant-derived flavor compounds, The Plant

Journal (2008) 54, 712732

4. Plant Biochemistry http://www.uky.edu/~dhild/biochem/lecture.html

Biosynthesis ofplant-derived flavor compounds


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Flavor compounds

Flavor molecules constitute a heterogeneousgroup of compounds, with straight-chain,

branched-chain, aromatic and heteroaromaticbackbones

bearing diverse chemical groups such as

hydroxyl, carbonyl, carboxyl, ester, lactone,amine, and thiol functions. More than 700 flavorchemicals have been identified and catalogued


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Chemical synthesis VS Biosynthesis

Most commercial flavorants are nature identical, whichmeans that they are the chemical equivalent of natural

flavors but are chemically synthesized, mostly frompetroleum-derived precursors

Bioproduction, including the extraction from natural sources,de novo microbial processes (fermentation), and bioconversionof natural precursors using micro-organisms or isolatedenzymes


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Biologicalfunctionsofplantvolatiles

Compoundsemittedbyflowersmostprobablyservetoattractandguidepollinators

volatiles might also protect the carbohydrate-rich nectar by inhibiting

microbialgrowth.vegetative plant tissue release volatiles following herbivore damage.Some of these substances attract arthropods that prey upon orparasitize the herbivores.

Volatiles also act as direct repellents or toxicants for herbivores andpathogens.

In fruits, volatile emission and accumulation facilitate seed dispersal byanimals and insects.

vegetative tissues often produce and release many of thevolatiles after their cells are disrupted. These volatile flavorcompounds may exhibit anti-microbial activity.

associatedwithdefensiveandattractiveroles


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Aromatic compounds responsible for odorand flavor of fruits comprise;

Alcohols

Carbonyls

Acids

Esters

Lactones

Phenols

R-OH

R-CHOR-CO-R

R-COOH

R-COO-R

R

O CO


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Estimated world

consumption of

selected aroma

chemicals in flavorand fragrancecompositions

CHO

OH

OCH3


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Calvin cycle


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N enters roots as NO- or NH+. The NH+ is incorporated into amino

acids in roots and leaves and the amino acids accumulate in proteins. Themain if not sole function of some proteins is to provide a store of amino

Amino acid synthesis


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Amino acid synthesis


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Glycolysis


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isoprenoid biosynthesis proceeds either via the"classical" or most well studied, mevalonate pathway

(cytosolic) (for the synthesis of sterols, sesquiterpenes,triterpenoids)

or via the non-mevalonate (-deoxy-D-xylulose--

phosphate, DXP) pathway for plastidic isoprenoids

(carotenoids, phytol [side-chain of chlorophyl ls], plastoquinone,isoprene, monoterpenes and diterpenes).


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Biosynthesis of flavors in vegetables and fruits

develop when tissue damage occurs

(Intact vegetable generally contains fewvolatiles)

Vegetable flavors

are formed during brief ripening period

Fruit flavors


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Minute quantities of lipids, CHO, protein (aminoacids) are enzymatically converted to volatile

flavors.

BIOGENESIS OF FRUIT AROMA

develops entirely during ripening period of plant


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FRUIT FLAVOR COMPOUNDS

Apple n-hexanal, ethyl butyrate, 1-propyl propionate,1-butyl acetate, trans-2-hexenal, ethyl 2-

methylbutyrate, 2-methylbutyl acetate, 1-

hexanol, hexen-1-ol, trans-2-hexen-1-ol, hexyl

acetate, Esters; alcohols; aldehydes; ketone;

acids; including hexanal; ethyl 2-methyl butyrate

Banana alcohols; esters, includingamylacetate,isoamyl

acetate, butylbutyrate, amylbutyrate

Peach Ethylacetate, dimethyldisulfide, cis--hexenylacetate, methyloctanoate, ethyloctanoate, -

pentylalphapyrone, gammadecalactone


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Lipids Polysaccharide Proteins/Enzymes Lignins

Aliphatic Terpenes Methyl-Branched Aromatic

Acids

Alcohols

Esters

Carbonyls

lactones

Sesquiterpenes

Hydrocarbons

Alcohols

Carbonyls

monoterpenes

Alcohols

Acids

Esters

carbonyls

Alcohols

Acids

Esters

carbonyls

Biosynthesis of fruit volatiles

Carbohydrate

Amino acid

Cinnamic acid

Terpene

Fatty acid

Acetyl-CoA

Malonyl CoAAcetyl CoAPyruvate

Mevalonyl CoA

Shikimic acid


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Flavorants from carbohydrate metabolism

Furanones and pyrones

fruit constituents

Only a limited number of natural volatiles

originate directly from carbohydrates withoutprior degradation of the carbon skeleton.


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Furanones and pyrones

Carbohydrate-derived flavor molecules, including-hydroxy-,-dimethyl-(H)-

furanone (furaneol), ,-dimethyl--methoxy-(H)-furanone (methoxyfuraneol), -

hydroxy--methyl-(H)-furanone (norfuraneol), -ethyl--hydroxy--methyl-(H)-

furanone (homofuraneol), -hydroxy--methylene--methyl-(H)- furanone (HMMF)and -hydroxy--methyl-H-pyran--on (maltol).


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Glycolysis

Glucose (C)

Pyruvate (C)

Ethanol LactateTCA Cycle

CO

+O

-O

-O



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Pyruvic acid CH3COCOOH

Acetic acid CH3COOH

Acetyl CoA CH3COSCoA

+ CO2

Malonyl CoA HOOCCH2COSCoA

Malonic Acid HOOCCH2COOH


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the most interesting is terpene biosynthesis

Terpenoids are enzymatically synthesized from acetyl CoA andpyruvate provided by the carbohydrate pools in plastids and thecytoplasm.

Terpenoids constitute one of the most diverse families of

natural products, with over 40 000 different structures of

terpenoids

Many of the terpenoids produced are non-volatile and areinvolved in important plant processes such as membranestructure (sterols), photosynthesis (chlorophyll side chains,carotenoids), redox chemistry (quinones) and growth regulation(gibberellins, abscisic acid, brassinosteroids)



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Important plant-derived volatile terpenoids .


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Biosynthesis of Terpenes

isoprene is derived from acetyl-CoA
http://images.google.co.th/imgres?imgurl=marchem.ep.sci.hokudai.ac.jp/damboo/isoprene.jpg&imgrefurl=http://marchem.ep.sci.hokudai.ac.jp/damboo/damboo.html&h=191&w=215&prev=/images%3Fq%3Disoprene%26svnum%3D10%26hl%3Dth%26lr%3D%26ie%3DUTF-8%26oe%3DUTF-8%26sa%3DG


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Classification of Terpenes


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Apocarotenoid formation

Carotenoid substrates are oxidatively cleaved to yield the apocarotenoid derivatives(right).


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Some of the volatile organic compounds in wine come from the grape's skin, orexocarp, while others come from the grape's flesh, or mesocarp. Organic acids give

wine its tartness, and sugars give it sweetness. Terpenes provide floral or fruity

flavors. Norisoprenoids impart a honeylike character. Thiols are the sulfur-based

compounds behind complex wine aromas such as guava, passionfruit or grapefruit

but when thiols go wrong, they can make a wine taste "funky."

Lipids


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products; acids, alcohols, diketones, ketones, esters of these compounds.

Lipids

metabolic pathway for lipid biosynthesis playsa significant role in flavor formation.

Alpha-, Beta-oxidation

Oxidation via lipoxygenase


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Lipoxygenase activity is believed to be themajor source of volatiles in plants.

Oxidation via Lipoxygenase

Major products: volatile C and C aldehydes and alcohols

Substrate: unsaturated fatty acid (linoleic and linolenic acids)

Lipoxygenase enzymes (dioxygenase) catalyze reactions

between O2 and polyunsaturated fatty acids


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Linolenic acid-derived flavor molecules.

AAT, alcohol acyl CoA transferase; ADH, alcohol dehydrogenase; AER, alkenaloxidoreductase; AOC, allene oxide cyclase; AOS, allene oxide synthase; HPL,

hydroperoxide lyase; JMT, jasmonate methyltransferase; LOX, lipoxygenase; OPR, -

oxo-phytodienoic acid reductase; Z,E-EI, Z,E-enal isomerase.


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Fatty acid precursors (Tomato)


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- and -oxidation of fatty acids

Palmitoyl-CoA (:)

Myristoyl-CoA (:)

+ Acetyl-CoA

the specific pathways in plants are not well understood

F f fl b d


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Formation of pear flavors via beta-oxidation


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Lactones


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Amino Acid Metabolism

Amino acid metabolism yields short chain aliphatic andaromatic alcohols, acids, carbonyls and esters

They are the primary source of branched chainaliphatic flavor compounds

their pathways have been barely analyzed in plants.


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amino acid precursors

(Tomato)

Biosynthesis of amino acid-derived


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(a) Catabolism of branched-chain amino acids leading to methyl branched flavor compounds, and

(b) postulated biosynthesis of sotolon. Formation of aldehyde (a) from amino acids requires the

removal of both carboxyl and amino groups. The sequence of these removals is not fully known

and could be the opposite to that shown or aldehyde could be formed in one step by aldehydesynthase

flavor compounds

S i i id i d h l l i d


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Starting amino acids: Tyrosine and phenylalanine products:phenolic/spicy in character

Shikimic acid formation


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Shikimic acid formation


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Vegetable Flavors


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Vegetable flavors

flavor again arises from major metabolic processes -e.g. Lipids, CHO & amino acids.

The role or importance of S compoundstovegetable flavor is quite significant.

the precursors, enzymes and end flavors are quitedifferent from fruits.

C b h d t


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Nonvolatile Precursors

Linoleic, Linolenic acid Thioglucosinolates Cysteine-sulfoxides Methyl-methionine

Precursor-splitting Enzymes

Lypoxygenase Thioglucosidases C-S-lyases None (Heating)

Carbonyls

Alcohols

Oxo-acids

Isothiocyanates

Nitriles

S C O

Thiocyanates

Polysulides

Alkyl-

thosulfinates

CH3-S-CH

3

Carbohydrate

Fatty acid Amino acid

Formation of flavor in vegetables


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Vegetable Flavor Categories

Genus Allium Enzymes produce volatiles from derivativesof cysteine (sulfoxides)

Genus Brassica Enzymes produce volatiles from glucosinolates

Alliaceous vegetables


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Alliaceous vegetables

garlic (Allium sativumL.)

onion (Allium cepaL.)

chive (Allium schoenoprasumL.)

leek (Allium porrumL.)


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Characteristic flavors

not exist in the bulb before processing

are produced when the cellular tissues areruptured by cutting or chewing

flavor is produced very rapidly by the actionof an enzyme on the odorless precursors whichcoexist in the cells


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O nion a nd G ar lic Flavor Enzymatic reaction of cysteine derivative


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GLUCOSINOLATES


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Glucosinolate precursors are important to theflavor of both the Brassica and Cruciferae family

Cruciferae family includes radish, horseradish,mustard.

GLUCOSINOLATES
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thiocyanate, nitrile, or isothiocyanate

& glucose

Hydrolysis of the glucosinolate

glucosinolate

thioglucosidase


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N l b l f h d i


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Natural carbon pools for the productionof flavor compounds, and the pathways


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Mevalonic acid Acetate Mevalonic acid

Isoprene

Shikimic acid Pyruvate + Erythrose phosphate



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the most interesting is terpene biosynthesis

most of essential oils get flavor from terpenoids ( carbon)

Limonene - a monoterpene hydrocarbon - is the major terpene inmany or most citrus products. Orange > % of the essential oil islimonene,

lemon ~ % limonene, yet is of little flavor significance.

Citral - oxygenated monoterpene - seldom comprises > % ofthe essential oil of lemon - largely carries the lemon flavor.



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Methane Undecane Henicosane Hentriacontane

Ethane Dodecane Docosane Dotriacontane

Propane Tridecane Tricosane Tritriacontane

Butane Tetradecane Tetracosane Tetracontane

Pentane Pentadecane Pentacosane Pentacontane

Hexane Hexadecane Hexacosane Hexacontane

Heptane Heptadecane Heptacosane Heptacontane

Octane Octadecane Octacosane Octacontane

Nonane Nonadecane Nonacosane Nonacontane

Decane Icosane Triacontane Hectane
http://www.acdlabs.com/iupac/nomenclature/79/r79_35.htm


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Isoamyl acetate, a strong fruity odor described assimilar to banana or pear

-Methyl-butyl acetate has a strong apple scent

Biosynthesis of Plant Derived Flavour

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