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Coumarine shikimate-derived

In the more complex structures, such as the furano-and pyranocoumarins, phenylcoumarins, and coumarin ethers, there are numerous instances in which other derivations, primarily from acetate, are known or presumed to be involved. In the present context the elaboration of these non-shikimate-derived residues is of secondary... [Pg.287]

Shikimates, which include phenylalanine, tyrosine, tryptophan, and their derivatives, are represented by many aromatic natural products, including hydroquinones found inbrownalgae such as Sargassum (Segawaand Shirahama 1987). Flavonoids are a structural class of shikimates found in plants, including isoflavonoids or neo-flavonoids, as is the y-pyrone (coumarin) core structure (Knaggs 2003). [Pg.12]

Phenylalanine Ammonia-Lyase. The building units of lignin are formed from carbohydrate via the shikimic acid pathway to give aromatic amino acids. Once the aromatic amino acids are formed, a key enzyme for the control of lignin precursor synthesis is phenylalanine ammonia-lyase (PAL) (1). This enzyme catalyzes the production of cinnamic acid from phenylalanine. It is very active in those tissues of the plant that become lignified and it is also a central enzyme for the production of other phenylpropanoid-derived compounds such as flavonoids and coumarins, which can occur in many parts of the plant and in many different organs (35). Radioactive phenylalanine and cinnamic acid are directly incorporated into lignin in vascular tissue (36). [Pg.10]

Coumarins and isocoumarins appear to be of varied origins. Simple coumarins, such as umbelliferone, are formed by the shikimic acid pathway in which hydroxylation of p-hydroxycinnamic acid occurs. Other coumarins, for example alternariol (690), are derived from a polyketide unit, as are a number of chromanones, chromones, pyranones and isocoumarins (B-78MI22400). The biosynthesis of 5-hydroxy-2-methylchromone has been shown to involve the chromanone (60JCS654). However, isocoumarins are also derived from the mixed acetate-shikimate route, through initial cyclization of the polyketide and subsequent lactonization. [Pg.876]

Phenylpropanoids have an aromatic ring with a three-carbon substituent. Caffeic acid (308) and eugenol (309) are known examples of this class of compounds. Phenylpropanoids are formed via the shikimic acid biosynthetic pathway via phenylalanine or tyrosine with cinnamic acid as an important intermediate. Phenylpropanoids are a diverse group of secondary plant compounds and include the flavonoids (plant-derived dyes), lignin, coumarins, and many small phenolic molecules. They are known to act as feeding deterrents, contributing bitter or astringent properties to plants such as lemons and tea. [Pg.490]

It has been noted that the chemical diversity of plant phenolics is as vast as the plant diversity itself. Most plant phenolics are derived directly from the shikimic acid (simple benzoic acids), shikimate (phenylpropanoid) pathway, or a combination of shikimate and acetate (phenylpropanoid-acetate) pathways. Products of each of these pathways undergo additional structural elaborations that result in a vast array of plant phenolics such as simple benzoic acid and ciimamic acid derivatives, monolig-nols, lignans and lignin, phenylpropenes, coumarins, stilbenes, flavonoids, anthocyanidins, and isollavonoids. [Pg.486]

Benzoic and cinnamic acid derivatives and flavonoids are the two most distributed phenolics within plants. Polyphenolic units are biosynthesized via shikimate pathway, resulting in cinnamic acids C -C phenylpropanoid building block that also contributes to other plant phenolics backbones such as those from flavonoids (Q-Ca-Ce), anthocyanidins (C6-C3-C6), and coumarins (C6-C3). Stilbeneoids (C6-C2-C6) and benzoic acid derivatives (Cfi-Ci) such as gallic and ellagic acids are also synthesized through this metabolic pathway (Fig. 1). [Pg.275]

Members of this group biogenetically originate from cinnamic acid derivatives via the shikimic acid pathway. They are all C-9 compounds having the 2H-l-benzopyran-2-one moiety in their skeleton. Coumarin itself has an unsubstituted basic skeleton. Compounds with hydroxyl or meth-oxyl substituents are described as simple coumarins. More... [Pg.1549]

The multibranched shikimic acid pathway provides the intermediates for the synthesis of the three amino acids phenylalanine, tyrosine and tryptophan in microorganisms and plants. In plants, these three amino acids are precursors for a variety of secondary metabolites such as alkaloids, coumarins, flavonoids, lignin precursors, indole derivatives and numerous phenolic compounds (Fig. 1). The role of the aromatic amino acids in protein synthesis is well known as is the role of indoleacetic acid in plant development however, the function of the various secondary products is much less clear. Various physiological roles have been proposed including pest resistance, chromagens in flowers and fruits, and precursors for the structural component, lignin. [Pg.147]

Direct evidence for the formation of coumarin from shikimate came from the radiotracer experiments of Kosuge and Conn in 1959, and they and others have also demonstrated cinnamic acid and a number of its ring-oxygenated derivatives, well known to originate from shikimate, to be precursors of various coumarins. The committed step in the biosynthesis of coumarins is hydroxylation of the benzene ring ortho to the side-chain of a cinnamic acid. In a few species the substrate is cinnamic acid itself, leading to the formation of coumarin, but for most coumarins, which bear 7-oxygenation, it is known or assumed that p-coumaric (4 -hydroxycinnamic) acid is the substrate, with discrete enzymes involved in the two cases. The product in the latter instance is 7-hydroxycoumarin (umbelliferone) ( 2, Fig. 1), and thus it is this compound rather than coumarin which, from the biosynthetic standpoint, is the parent compound of the vast majority of coumarins. [Pg.289]

The common structural features of many coumarins argue in favour of a common biogenesis. The biosynthesis of a number of simple coumarins has been studied sufficiently to permit the generalisation that they are derived from the corresponding cinnamic acids, these being formed via the shikimic acid pathway 105, 108, 242, 419, 567). [Pg.208]

On the basis of this and the other biosynthetic evidence, Kominek has identified the rate limiting steps in the biosynthesis of novobiocin as the formation of the coumarin (123) and p-hydroxybenzoic acid from (—)-shikimic acid. He proposed a pathway of biosynthesis (Figure 4.19) in which the final step is condensation of the noviosyl coumarin (124) and the p-hydroxy-benzoic acid derivative (125). [Pg.173]


See other pages where Coumarine shikimate-derived is mentioned: [Pg.149]    [Pg.144]    [Pg.306]    [Pg.358]    [Pg.121]    [Pg.197]    [Pg.303]    [Pg.11]    [Pg.287]    [Pg.289]    [Pg.4545]    [Pg.141]    [Pg.190]   
See also in sourсe #XX -- [ Pg.149 ]




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