Cinnamic acid, hydroxy derivatives

Recent scientific investigations of natural polyphenols have demonstrated their powerful antioxidant property (Niki et al, 1995). Several classes of polyphenols have been chemically identified. Some of these are grape polyphenols, tea polyphenols, soy polyphenols, oligomeric proanthocyanidines (OPA) and other natural polyphenols of the flavone class. Rice bran polyphenols are different from the above in that they are p-hydroxy cinnamic acid derivatives such as p-coumaric acid, ferulic acid and p-sinapic acid. Tricin, a flavone derivative, has also been isolated from rice bran. 

There are several examples in the literature where similar cis-trans isomerizations of o-hydroxy cinnamic acid derivatives have been used to deliver fragrances. For example, ester 76, which was absorbed into cloth and exposed to sunlight, released its fragrant alcohol moiety, whereas samples that were stored in the dark did not... 

Flavone glycosides often occur as acylated derivatives either with aliphatic or aromatic acids. Hydroxy-cinnamic acid derivatives are the most frequent in nature and MS fragmentations of these types of compounds show ions produced by the loss of 146,162,176, or 206 m.u., corresponding to the losses of the acyl residues />-coumaroyl, caffeoyl, femloyl, or sinapoyl, respectively. Brassicaceae species are rich in flavonoid glycosides acylated with hydroxyl-cinnamic derivatives, and most of them... 

A series of related experiments (74), in which various labeled 4 -hydroxy-cinnamic acid derivatives (151-1 were administered in admixture wiA different members of the series in unlabeled form as trapping agents, led to the following two conclusions ... 

CS133 Imperato, F. N-P-coumarylglutamic acid, an unusual hydroxy cinnamic acid-aminoacid derivative from black CS143 tea. Chem Ind (London) 1980 388. 

Two mechanisms have been proposed for the Knoevenagel reaction. In one, the role of the amine is to form an imine or iminium salt (378) which subsequently reacts with the enolate of the active methylene compound. Under normal circumstances elimination of the amine would give the cinnamic acid derivative (379). However, when an o-hydroxy group is present in the aromatic aldehyde intramolecular ring closure to the coumarin can occur. The timing of the various steps may be different from that shown (Scheme 118). 

Coumaric Acid, Coumarinic Acid or Hydroxy-cinnamic Acid [called Cumarsaure, Cumarinsaure, (Oxyphenyl)-acrylsaure or Oxy-zimtsaure in Ger], CgH803 mw 164-15, O 29-24%. This compd exists as ortho-, meta - para - derivs. The ortho deriv is known in both trans cis forms ... 

Schmidt et al. found that a distinct product phase appeared at less than 10% conversion in some cases (indicating heterogeneous reaction), while in others none was evident at greater than 70% conversion [63]. Certain derivatives, (3-truxinic acids in particular, were formed in a modification different from that into which they could be recrystallized. Schmidt interpreted these results in terms of a phase separation of the forming product which occurs when it reaches a limiting solubility in the lattice of the reactant. He further pointed out that recrystallization may be necessary to improve yields in the dimerization of 0-cinnamic acids in certain instances where monomer molecules may be stranded in nonreactive sites such as M2.. M.. M2 (Section IV.B.5.). 5-Bromo-2-hydroxy-cinnamic acid is an example of a case where there is no evidence for phase separation and reaction is found to be slow and proceed in low yield [63,108]. 

Cinnamic acid derivatives 960—see also 2,4-Dimethoxycinnamic acid esters Cinnamic acids—see Hydroxycinnamic adds, tratts-4-Hydroxy-a-cyanocinnamic acid Circular dichroism 992 Claisen condensation,... 

Basic catalysts other than alkali acetates have been employed in the Perkin reaction thus salicylaldehyde condenses with acetic anhydride in the presence of triethylamine to yield coumarin (the lactone of the cis form of o-hydroxy-cinnamic acid) together with some of the acetyl derivative of the trans form (o-acetoxycoiimaric acid) ... 

Hagel,J.M. and P.J.Facchini Elevated tyrosine decarboxylase and tyramine hydroxycinnamoyltransferase levels increase wound-induced tyramine-derived hydroxy-cinnamic acid amide accumulation in transgenic tobacco leaves Planta 221 (2005) 904-914. 

The 2-hydroxy cinnamic acid esters (21a) and (21b) in contrast yield the enol acetate derivatives (22a) and (22b) respectively, after acetylation. 

As p-hydroxy-cinnamic acid can exist in either the or trans configuration, both were tested. The data (Table III) showed that the -isomer was more active than the trans-isomer. Saturation of the double bond in the aliphatic portion of the molecule was investigated by testing the dihydro-derivatives of p-hydroxycinnamic and 3,4-dihydroxycinnamic acids. The dihydro-acids were slightly more active than the corresponding cinnamic compounds. 

In addition to the inhibitory effect of cinnamic acid derivatives on the PAL activity, they generally lower the amount of extractable PAL. This has been studied in (a) feeding experiments, (fo) experiments in which the hydroxy-cinnamic acids were converted in vivo into other products, and (u) experiments in which the accumulation of cinnamic acid derivatives was prevented by in-vivo inhibition of PAL activity. 

Korosec B, Sova M, Turk S, Krasevec N, Novak M, Lah L, Stojan J, Podobnik B, Berne S, Zupanec N et al (2014) Antifungal activity of cinnamic acid derivatives involves inhibition of benzoate 4-hydroxy-lase (CYP53). J Appl Microbiol 116 955-966... 

Phenolic compounds are widely distributed in plant parts from the roots to the seeds and include phenolic acids, flavo-noids and tannins. The tannins may reduce protein digestibility (Ford and Hewitt, 1979) and perhaps the bioavailability of other nutrients. The flavonoids have been reported to have a number of nutritional and pharmacological activities (Kuhnau, 1976). Phenolic acids include benzoic and cinnamic acid derivatives. The benzoic acid derivatives include p-hydroxy-benzoic, protochate-chuic, vanillic, gallic and syringic acids. The cinnamic acids, p-coumaric, caffeic, ferulic and sinapic are found in most oilseeds used to prepare protein concentrates and frequently occur in the form of esters with quinic acid or sugars. Chlorogenic acid for example is an ester of caffeic acid and quinic acid and is found in several isomeric and derivatized forms. 

Fig. 2.4 Some common simple plant phenolic adds, cinnamic acid derivatives on the right and benzoic acid derivatives on the left, where H equals hydrogen, OH equals hydroxy, and OMe equals methoxy...

Hydroxyl-functionalized cinnamic acid derivatives such as p-coumaric acid (p-hydroxycinnamic acid), ferulic acid, and sinapinic acid are attractive monomers for syntheses of high-performance polyesters. The obtained polyesters are also expected to be biodegradable in the case of copolymerization with aliphatic hydroxy acids such as lactic acid. Tanaka et al reported the thermal polycondensation of p-coumaric acid at 550 °C without any catalyst under high pressure up to 80 kbar (in the solid state) in 1975. They obtained red or brownish-red hard solids insoluble in conventional organic solvents. Higashi and his co-workers synthesized copolyesters of p-coumaric acid and 4-hydroxybenzoic acid or their methoxy substitutions (ferulic acid, vanillic acid, or syringic acid) by polycondensation using hexachlorocyclotri(phosphazene) in pyridine in 1981. The obtained polymers that exhibited UV spectra different... 

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