Phenylpropanoid alkaloids

L-norepinephrine and dopamine are present in some plants and act as agonists for both a- and P-adrenergic receptors [1]. Further plant P-adrenergic receptor agonists include the phenylpropanoid alkaloids L-... 

Natural products presumably biosynthesized through a [4 + 2] cycloaddition frequently occur in the literature. Several reviews on natural Diels-Alder-type cycloadducts covered more than 300 cycloadducts, including polyketides, terpenoids, phenylpropanoids, alkaloids, and natural products formed through mixed biosynthetic pathways. Representative examples of natural [4 + 2] adducts are shown in Figure 1. These include intramolecular adducts pinnatoxin (5) and nargenicin (6), a simple intermolecular adduct... 

Small molecule OMT enzymes from plants are classified in two distinct groups. Group I OMTs have molecular weights in the range of 38 3 KDa and target many acceptors such as flavonoids, phenylpropanoids, alkaloids, and coumarins. Group II OMTs are of lower molecular weight (23-27 KDa) and are dependent on Mg for activity [108]. 

Achenbach H, Hemrich H. Alkaloids, flavonoids and phenylpropanoids of the West African plant Oxymitra velutina. Phytochemistry 1991 30 1265-1267. 

In addition, it has been discovered that there are naturally occurring enzymes that facilitate Diels-Alder type reactions within certain metabolic pathways and that enzymes are also instrumental in forming polyketides, isoprenoids, phenylpropanoids, and alkaloids (de Araujo et al., 2006). Agresti et al. (2005) identified ribozymes from RNA oligo libraries that catalyzed multiple-turnover Diels-Alder cycloaddition reactions. 

Plant metabolism can be separated into primary pathways that are found in all cells and deal with manipulating a uniform group of basic compounds, and secondary pathways that occur in specialized cells and produce a wide variety of unique compounds. The primary pathways deal with the metabolism of carbohydrates, lipids, proteins, and nucleic acids and act through the many-step reactions of glycolysis, the tricarboxylic acid cycle, the pentose phosphate shunt, and lipid, protein, and nucleic acid biosynthesis. In contrast, the secondary metabolites (e.g., terpenes, alkaloids, phenylpropanoids, lignin, flavonoids, coumarins, and related compounds) are produced by the shikimic, malonic, and mevalonic acid pathways, and the methylerythritol phosphate pathway (Fig. 3.1). This chapter concentrates on the synthesis and metabolism of phenolic compounds and on how the activities of these pathways and the compounds produced affect product quality. 

FRICK, S., KUTCHAN, T.M., Molecular cloning and functional expression of O-methyltransferases common to isoquinoline alkaloid and phenylpropanoid biosynthesis, Plant J., 1999,17, 329-339. 

One current estimate of NP diversity totals ryo.ooo different structures, yet this huge chemical diversity is generated from only a few biochemical pathways that branch from the metabolism shared by most organisms. About 60% of the known NP diversity comes from one ancient pathway (the isoprenoids or terpenoids), another 30% comes from some other ancient pathways related to each other (the polyphenols, phenylpropanoids or polyketides) and less than 10% of NPs (alkaloids) comes from a more diverse family of pathways. There seems to be a rough correlation between the number of species possessing one pathway and the total diversity of NPs made by that route. Consequently, the minor groups of NPs that comprise less than 1% of the total NP diversity (e.g., the glucosinolates) tend to be restricted to a small number of species. 

This body of evidence led to the conclusion that two intact C6-C3 units derived from phenylalanine are incorporated into lactonic Lythraceae alkaloids. One unit is the precursor of the phenylpropanoid part of the alkaloids (C-l 1 to C-19) and the other gives rise to the C-3 to C-l, C-20 to C-25 segment of the phenylquinolizidine part ... 

Methylation is one of the most common enzymatic modifications in plant specialized (secondary) metabolism. Almost all classes of plant specialized metabolites are known to be methylated, including amino acids, alkaloids, phenylpropanoids, sugars, purines, sterols, thiols, and flavonoids. The methyl transfer most commonly occurs on C, N, S, or O atoms. 

Isoquinoline alkaloids Phenylpropanoids Flavonoids, stibenes, catechins Lignin, lignans Coumarins, furanocoumarins Cyanogenic glycosides Glucosinolates Quinones,... 

Taxane alkaloids are made up of a terpenoid core and a phenylpropanoid (3-amino acid, joined by an ester bond. They can be classified according to the carbon-carbon connectivity of the terpenoid core and the type of the side-chain. Thus, the diterpenoid core can be of the taxane- (Tables 3-8), 11 (151 )abeotaxane-(Table 10), 2(3->20)abeotaxane-(Table 2) or 3-11-cyclotaxane (Table 9) type, whereas the side chain can be Winterstein s add [L(R) (3-dimethylamino-P-phenylpropionic add] or N, A/-dimethylphenylisoserine (2R, 3S (threo) a-hydroxy-3-dimethylamino-P-phenylpropionic acid). Further modification occurs in the... 

Flavonoid conjugates, aromatic carboxylic acids, alkaloids, phenylpropanoids Tomato peel and flesh LC-PDA-TOF MS 83... 

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