Cinnamic acids p-coumaric acid

Simple phenolic compounds include (1) the phenylpropanoids, trans-cinnamic acid, p-coumaric acid and their derivatives (2) the phenylpropanoid lactones called coumarins (Fig. 3.4) and (3) benzoic acid derivatives in which two carbons have been cleaved from the three carbon side chain (Fig. 3.2). More complex molecules are elaborated by additions to these basic carbon skeletons. For example, the addition of quinic acid to caffeic acid produces chlorogenic acid, which accumulates in cut lettuce and contributes to tissue browning (Fig. 3.5). 

R = H, Cinnamic Acid R- OHy p-Hydroxy-cinnamic Acid (p -Coumaric Acid)... 

Cinnamic acid p-Coumaric acid m-Coumaric acid o-Coumarie acid... 

Table 5 Different solvent systems were used as developers for thin layer chromatographic separation for simple phenolic and related compounds as cinnamic acid, p-coumaric acid, ferulic acid, and tannic acid...

Biosynthesis of flavonoids starts with the conversion of phenylalanine or tyrosine to cinnamic acid by phenylalanine ammonia lyase (PAL) (Hahlbrock and Grisebach, 1975). Subsequent reactions are catalyzed by cinnamic acid 4-hydrolase to form 4-hydroxyl cinnamic acid (p-coumaric acid). The p-coumaric acid is then catalyzed by p-coumarate CoA ligase to form p-coumaroyl CoA. 

Tracer studies with labeled phenylalanine and with tyrosine have shown that these are specifically incorporated. Intermediates in this biosynthesis are tryamine, cinnamic acid, p-coumaric acid, and caffeic acid 11). 

The vinyl-phenols in white wines are formed due to enzymic decarboxylation by yeast of two cinnamic acids (p-coumaric acid and ferulic acid) in must, producing vinyl-4-phenol and vinyl-4-guaiacol, respectively (Figure 8.6). 

A group of indole alkaloids from Mesembryanthe-mum species. (-)-Mesembrine, [C17H23NO3, Mr 289.37, oil, bp. 186-190°C (40 Pa), [a)g -55.4° (CH3OH)] has a cocaine-like activity. The plants are used in South West Africa to prepare the drug Channa. Joubertiamine (C,3H, N02, Mr 245.32) occurs together with mesembrine. The biosynthesis of M. a. is similar to that of Amaryllidaceae alkaloids of the cri-nine group and proceeds from phenylalanine via cinnamic acid, p-coumaric acid, and 3-(4-hydroxy-phenyOpropanoic acid. The latter is then coupled with yV-methyltyramine. 

Some Amaryllidaceae plants possess a group of alkaloids containing a Cg— C2-N-C1-C6 unit. In this unit, the C6-C2-N moiety is derived from tyrosine or tyramine, and the C -Ci part is derived from phenylalanine through cinnamic acid, p-coumaric acid, and protocatechualdehyde [1]. Tyramine (C6-C2-N unit) and protocatechualdehyde (C -Ci unit) are then combined and methylated to form O-methylnorbelladine, which is a common biosynthetic precursor of various Amaryllidaceae alkaloids. Through para,ortho -, ortho,para - and para,paw-phenol coupling of norbel-ladine, the lycorine, galanthamine, and crinine type alkaloids are formed, respectively [2]. 

Cinnamic Acid, p-Coumaric acid, and Related Compounds BiosynAesis Physiological Roles... 

Cinnamic acid, p-coumaric acid (2), and several related compounds modify growtii in plants (also see Section 8.8). 

Higher plants accumulate a wide range of phenolic compounds that are derivatives or metabolites of cinnamic acid. The phenyl-propanes, generally denoted as C -C compounds, are important intermediates in the biosynthesis of lignin and flavonoids. The common phenylpropane derivatives cinnamic acid, p-coumaric acid, caffeic acid, ferulic acid, 5-hydroxyferulic acid, and sinapic acid, are interrelated and are synthesized from phenylalanine (Fig. 5). 

Cinnamic acid and Hydroxy cinnamic acids. The biosynthetic sequence cinnamic acid —> p-coumaric acid caffeic acid —> ferulic acid — 5-hydroxy-ferulic acid -> sinapic acid (Eig. 6.3) includes progressive hydroxylation at the... 

Biosynthesis of Plant Phenoiics. Phenolic compounds in plant foods are secondary metabolites which are derived from phenylalanine, and in some plants from tyrosine via enzymatic deamination assisted by ammonia lyase (Figure 1). Phenylpropanoids, the first products of deamination of phenylalanine and/or tyrosine consist of a phenyl ring (C ) and a 3 carbon side chain (C,). These Q-C, compounds may subsequently undergo hydroxylation in the phenyl ring and possibly subsequent methylation. This would lead to the formation of a large number of products which include cinnamic acid, p-coumaric acid, caffeic acid, ferulic acid and sinapic acid (5). 

All findings up to now indicate that all other coumarins are formed in the same way from the corresponding substituted cinnamic acid, p-Coumaric acid furnishes umbelliferone, caffeic acid aesculetin and ferulic acid scopoletin (Fig. 99). Thus, our reaction scheme (Fig. 98) is generally valid, the appropriate ring substituents have simply to be inserted. The mode of biosynthesis provides us with an explanation of the fact that the most important cinnamic acids and coumarins exhibit the same pattern of substitution. 

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