Presentation on theme: "Biosynthesis of Plant-derived flavor compounds By Dudsadee Uttapap."— Presentation transcript:
Biosynthesis of Plant-derived flavor compounds By Dudsadee Uttapap
References 1. “Flavor Chemistry and Technology”, H.B. Heath, G. Reineccius, “Flavor Chemistry”, D.B. Min, 3.“Biosynthesis of plant-derived flavor compounds”, The Plant Journal (2008) 54, 712–732 4.“Plant Biochemistry” Biosynthesis of plant-derived flavor compounds
Flavor compounds Flavor molecules constitute a heterogeneous group of compounds, with straight-chain, branched-chain, aromatic and heteroaromatic backbones bearing diverse chemical groups such as hydroxyl, carbonyl, carboxyl, ester, lactone, amine, and thiol functions. More than 700 flavor chemicals have been identified and catalogued
Chemical synthesis VS Biosynthesis Most commercial flavorants are ‘nature identical’, which means that they are the chemical equivalent of natural flavors but are chemically synthesized, mostly from petroleum-derived precursors Bioproduction, including the extraction from natural sources, de novo microbial processes (fermentation), and bioconversion of natural precursors using micro-organisms or isolated enzymes
Biological functions of plant volatiles Compounds emitted by flowers most probably serve to attract and guide pollinators volatiles might also protect the carbohydrate-rich nectar by inhibiting microbial growth. vegetative plant tissue release volatiles following herbivore damage. Some of these substances attract arthropods that prey upon or parasitize the herbivores. Volatiles also act as direct repellents or toxicants for herbivores and pathogens. In fruits, volatile emission and accumulation facilitate seed dispersal by animals and insects. vegetative tissues often produce and release many of the volatiles after their cells are disrupted. These volatile flavor compounds may exhibit anti-microbial activity. “associated with defensive and attractive roles”
Aromatic compounds responsible for odor and flavor of fruits comprise; Alcohols Carbonyls Acids Esters Lactones Phenols R-OH R- CHO R-CO-R’ R-COOH R-COO-R’ R OCOR OCO
Estimated world consumption of selected aroma chemicals in flavor and fragrance compositions
N enters roots as NO3- or NH4+. The NH4+ is incorporated into amino acids in roots and leaves and the amino acids accumulate in proteins. The main if not sole function of some proteins is to provide a store of amino acids Amino acid synthesis
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 (1-deoxy-D-xylulose-5- phosphate, DXP) pathway for plastidic isoprenoids (carotenoids, phytol [side-chain of chlorophylls], plastoquinone, isoprene, monoterpenes and diterpenes).
Biosynthesis of flavors in vegetables and fruits develop when tissue damage occurs (Intact vegetable generally contains few volatiles) Vegetable flavors are formed during brief ripening period Fruit flavors
Minute quantities of lipids, CHO, protein (amino acids) are enzymatically converted to volatile flavors. BIOGENESIS OF FRUIT AROMA develops entirely during ripening period of plant
Biosynthesis of fruit volatiles Carbohyd rate Amino acid Cinnamic acid Terpe ne Fatty acid Acetyl- CoA Malonyl CoA Acetyl CoA Pyruva te Mevalonyl CoA Shikimic acid
Flavorants from carbohydrate metabolism Furanones and pyrones “fruit constituents” Only a limited number of natural volatiles originate directly from carbohydrates without prior degradation of the carbon skeleton.
Furanones and pyrones Carbohydrate-derived flavor molecules, including 4-hydroxy-2,5-dimethyl-3(2H)- furanone (furaneol), 2,5-dimethyl-4-methoxy-3(2H)-furanone (methoxyfuraneol), 4- hydroxy-5-methyl-3(2H)-furanone (norfuraneol), 2-ethyl-4-hydroxy-5-methyl-3(2H)- furanone (homofuraneol), 4-hydroxy-2-methylene-5-methyl-3(2H)- furanone (HMMF) and 3-hydroxy-2-methyl-4H-pyran-4-on (maltol).
Glycolysis Glucose ( 6 C) 2 Pyruvate ( 3 C) EthanolLactate TCA Cycle CO 2 +O 2 -O 2 Flavorants from carbohydrate metabolism
“the most interesting is terpene biosynthesis” Terpenoids are enzymatically synthesized from acetyl CoA and pyruvate provided by the carbohydrate pools in plastids and the cytoplasm. Terpenoids constitute one of the most diverse families of natural products, with over different structures of terpenoids Many of the terpenoids produced are non-volatile and are involved in important plant processes such as membrane structure (sterols), photosynthesis (chlorophyll side chains, carotenoids), redox chemistry (quinones) and growth regulation (gibberellins, abscisic acid, brassinosteroids) Flavorants from carbohydrate metabolism
Important plant-derived volatile terpenoids.
Biosynthesis of Terpenes “isoprene is derived from acetyl-CoA”
Classification of Terpenes
Apocarotenoid formation Carotenoid substrates are oxidatively cleaved to yield the apocarotenoid derivatives (right).
Some of the volatile organic compounds in wine come from the grape's skin, or exocarp, 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."
products; acids, alcohols, diketones, ketones, esters of these compounds. Lipids metabolic pathway for lipid biosynthesis plays a significant role in flavor formation. Alpha-, Beta-oxidation Oxidation via lipoxygenase
Lipoxygenase activity is believed to be the major source of volatiles in plants. Oxidation via Lipoxygenase Major products: volatile C6 and C9 aldehydes and alcohols Substrate: unsaturated fatty acid (linoleic and linolenic acids). Lipoxygenase enzymes (dioxygenase) catalyze reactions between O 2 and polyunsaturated fatty acids
- and -oxidation of fatty acids Palmitoyl-CoA (16:0) Myristoyl-CoA (14:0) + Acetyl-CoA the specific pathways in plants are not well understood
Formation of pear flavors via beta-oxidation
Amino Acid Metabolism Amino acid metabolism yields short chain aliphatic and aromatic alcohols, acids, carbonyls and esters They are the primary source of branched chain aliphatic flavor compounds their pathways have been barely analyzed in plants.
amino acid precursors (Tomato)
(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 aldehyde synthase Biosynthesis of amino acid-derived flavor compounds
Starting amino acids: Tyrosine and phenylalanine products: phenolic/spicy in character
Shikimic acid formation
Vegetable flavors flavor again arises from major metabolic processes - e.g. Lipids, CHO & amino acids. The role or importance of S compounds to vegetable flavor is quite significant. the precursors, enzymes and end flavors are quite different from fruits.
Carbohydrate Fatty acidAmino acid Formation of flavor in vegetables
Vegetable Flavor Categories Genus Allium Enzymes produce volatiles from derivatives of cysteine (sulfoxides) Genus Brassica Enzymes produce volatiles from glucosinolates
Alliaceous vegetables garlic (Allium sativum L.) onion (Allium cepa L.) chive (Allium schoenoprasum L.) leek (Allium porrum L.)
Characteristic flavors not exist in the bulb before processing are produced when the cellular tissues are ruptured by cutting or chewing flavor is produced very rapidly by the action of an enzyme on the odorless precursors which coexist in the cells
Onion and Garlic Flavor Enzymatic reaction of cysteine derivative
Glucosinolate precursors are important to the flavor of both the Brassica and Cruciferae family Cruciferae family includes radish, horseradish, mustard. GLUCOSINOLATES
thiocyanate, nitrile, or isothiocyanate & glucose Hydrolysis of the glucosinolate glucosinolate thioglucosidase
Natural carbon pools for the production of flavor compounds, and the pathways
“the most interesting is terpene biosynthesis” most of essential oils get flavor from terpenoids (10 carbon) Limonene - a monoterpene hydrocarbon - is the major terpene in many or most citrus products. Orange > 95% of the essential oil is limonene, lemon ~ 65% limonene, yet is of little flavor significance. Citral - oxygenated monoterpene - seldom comprises > 2% of the essential oil of lemon - largely carries the lemon flavor. Flavorants from carbohydrate metabolism