Cinnamic acids caffeic

Garcia-Granda, S., Beurskens, G., Beurskens, P. T., Krishna, T. S. R., and Desiraju, G. R. Structure of 3,4-dihydroxy-frnns-cinnamic acid (caffeic acid) and its lack of solid-state topochemical reactivity. Acta Cryst. C43, 683-685 (1987). 

In this chapter, we will discuss in brief about caffeic acid and compounds derived from it. Caffeic acid is regarded as the commonest of phenolic compounds distributed in plant flora, ft is produced by hydroxylation of cinnamic acid. Caffeic acid is distributed in Coffea arabica, Echinacea purpurea and Cichorium intybus. Qunic acid is the degradation product of caffeic acid. Chlorogenic acid is a dark coloured pigment and is most abundant phenolic compound in plants next to caffeic acid. It is known to cause allergic dermatitis among humans. 

The conversion of phenylalanine to a C-6—C-1 unit must include a process for the loss of two earbon atoms of the aromatic side chain as well as the introduction of oxygen in the aromatic ring. From previous biochemical studies two possible pathways seemed feasible for degradation to a C-6—C-1 unit (a) phenylalanine->phenylserine->benzalde-hyde- protocatechuic aldehyde, or (6) phenylalanine- cinnamic acid- -caffeic acid->protocatechuic aldehyde. The negligible incorporation of benzaldehyde and phenylserine compared with protocatechuic aldehyde... 

Highest average phenolic acid concentration recovered from Cecil A soil samples was 4 p.g/g soil for p-coumaric acid, a cinnamic acid. In general benzoic acids (vanillic, p-hydroxybenzoic acid, and sinapic acid) were higher in concentration than cinnamic acids (caffeic acid, ferulic acid, and syringic acid), with the exception of p-coumaric acid. 

Hydroxycinnamic acids (HCAs) are a major class of phenolic compounds found in nature. They are secondary metabolites derived from tyrosine and phenylalanine, which have a C6-C3 carbon skeleton with a double bond in the side chain that may have a trans or cis configuration (Figure 3.11) [55]. Among the most common and well known HCAs are cinnamic acid, caffeic acid, ferulic acid, m-coumaric acid, o-coumaric acid, p-coumaric acid, and sinapic acid. 

One of the most important substances derived from tetrahydrox-ycyclohexane is (lS,3J ,4S,5J )-l,3,4,5-tetrahydroxycyclohexane-1-carboxylic acid, known as (-)-L-quinic acid (8-70). The trihydroxycyclohexene derivative is related (3ii,4S,5Ji)-3,4,5-trihydroxycyclohex-l-ene-1-carboxylic acid known as (-)-l-shikimic acid (8-71), which is a key intermediate in the biosynthesis of phenolic compounds. As free acids, but mainly as esters (depsides) with ( )-cinnamic acids (caffeic, ferulic and... 

The main aromatic carboxyKc acids of coffee are chlorogenic acids, esters (depsides) of L-quinic acid with predominantly (E)-cinnamic acid, caffeic, ferulic and 4-coumaric acids. In smaller amounts, chlorogenic acids are found in tea, cocoa, apples and pears, in other fruits and in vegetables and potatoes. 

Effects of Allelochemlcals on ATP Supply. Allelochemlcals might decrease the ATP content of tissue by either increasing ATP utilization or decreasing ATP production. Some allelochemlcals that inhibit mineral absorption decrease ATP content of plant tissues. Salicylic acid decreased the ATP content of oat roots in a pH dependent manner (Figure 3). This result suggested that mitochondrial production of ATP was decreased in the tissue. On the other hand, Tillberg (38) found that salicylic acid and cinnamic acid increased the ATP content of Scenedesmus. Various flavonoids inhibited ATP production by mitochondria Isolated from cucumber (Cucumls satlvus L.) hypocotyls (54). Flavones such as kaempferol were more inhibitory than the corresponding flavanones. Substituted cinnamic acids such as caffeic acid were not inhibitory. 

Hydroxy cinnamic acids are included in the phenylpropanoid group (C6-C3). They are formed with an aromatic ring and a three-carbon chain. There are four basic structures the coumaric acids, caffeic acids, ferulic acids, and sinapic acids. In nature, they are usually associated with other compounds such as chlorogenic acid, which is the link between caffeic acid and quinic 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). 

A series of subsequent reactions after PAL first introduces a hydroxyl at the 4-position of the ring of cinnamic acid to form p- or 4-coumaric acid (i.e., 4-hydroxycinnamic acid). Addition of a second hydroxyl at the 3-position yields caffeic acid, whereas O-methylation of this hydroxyl group produces ferulic acid (see Fig. 3.3). Two additional enzymatic reactions are necessary to produce sinapic acid. These hy-drocinnamic acids are not found in significant amounts in plant tissue because they are rapidly converted to coenzyme A esters, or glucose esters. These activated intermediates form an important branch point because they can participate in a wide range of subsequent reactions. 

Caffeic acid (3,4-dihydroxy cinnamic acid) +0.4 glassy carbon 268 85... 

Cinnamic acid OH derivatives H J> H Caffeic acid / -Coumaric acid o-Coumaric acid CH Ferulic acid Cinnamic acid Sinapinic acid COOH Flavonoids Flavones Apigenin q JT 11 Luteolin R2 Flavanonol 1 i IJ R3 V >r (+)-Taxifolin OH 0... 

Figure 6.6 HPLC chromatogram of the extract from Superior potato flesh (a) and of the same extract spiked with standards (b). Identification p.1, chlorogenic acid p.2, chlorogenic acid isomer p.3, caffeic acid p.4, p-coumaric acid p.5, ferulic acid p.6, t-cinnamic acid. Column, Inertsil ODS-3 V (5 p.m, 4.0 X 250 mm) flow rate, l.OmL/min column temperatures, 20°C mobile phase, acetonitrile 0.5% formic acid (gradient mode) detector, UV at 280 nm.

Figure 6.8 UV spectra of standard chlorogenic acid (a) trans-cinnamic acid (b) cafFeic acid (c) p-coumaric acid (d) and femlic acid (e). The spectra of peaks 1 (chlorogenic acid) (f), peak 2 (chlorogenic acid isomer) (g), and peak 3 (caffeic acid) (h) were determined with HPLC fractions isolated from extracts of Superior potato peel.

The most common cinnamic acids are caffeic (3,4-dihydroxycinnamic acid), ferulic (3-methoxy-4-hydroxy), sinapic (3,5-dimethoxy-4-hydroxy) and p-coumaric (4-hydroxy) acid, Table 4 [13]. 

After oral administration of caffeic acid to rats, small amounts of vanillic acid and vanilloylglycine are excreted. The conversion of p-hydroxycinnamic acid into /7-hydroxybenzoic acid is found in rat liver mitochondria [18], Studies with /7-hydroxy[U-14C]cinnamic acid have showed that 14C02 is released during reaction, indicating that reaction probably followed the p-oxidation type reactions, the two carbon being first removed as acetyl-CoA, and then oxidized to C02. It is assumed that conversion of ferulic acid formed by methylation of caffeic acid into vanillic acid occurs in rat liver mitochondria. 

A pure culture of the organism was inoculated into a basal medium with the addition of 0.025% caffeic acid. After 7 days incubation at 25°C under conditions of reduced oxygen tension, the caffeic acid was completely metabolized. Metabolites of caffeic acid are identified as dihydrocaffeic acid and ethyl catechol, respectively. In the 1960s, it has been reported that a constitutive enzyme present in strains of Aerobacter decarboxylates caffeic acid to 4-vinylcatechol nonoxidatively [20], Several cinnamic acids have been tested and the decarboxylation product from /7-coumaric acid has been identified as 4-vinylphenol. Thus, the bacterial enzyme activity requires a relatively unhindered 4-hydroxy group on the aromatic ring and an acrylic acid side chain. 

For white wines (85), a similar HPLC condition to that of Betes-Saura et al. (79) was employed with a Nucleosil C)8 column (250 X 4.0-mm ID, 5 /zm) with binary gradient using eluent (A) acidified water (pH 2.65) and eluent (B) 20% A with 80% acetonitrile applied for hydroxy-cinnamate derivatives esters (caffeoyl tartaric, p-coumaroyl tartaric, and feruloyl tartaric acid esters) and free hydroxycinnamic acids (caffeic, ferulic, and p-coumaric acids). 

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