Hydroxycinnamic derivatives

The reduction of a-tocopheroxyl radical by polyphenols is dependent on their structure. This has been critically shown for hydroxycinnamates, caflfeic, and /t-coumaric acids, the latter missing one of the -OH groups of the catecholic moiety. Although caffeic acid efficiently reduces a-tocopheroxyl radical to a-TOH, />-coumaric acid increases the rate of a-TOH consumption, and a clear synergistic protection of LDL from oxidation is observed only with caffeic acid plus a-TOH (Laranjinha et al, 1995). This effect of j9-coumaric acid was interpreted in terms of the stability of hydroxycinnamates-derived phenoxyl radicals and is supported by the higher reduction potential of /t-coumaric radical as compared with that of caffeic radical (Foley et al, 1999). Thus, conversely to caffeic acid o-semiquinone radical, j7-coumaric acid phenoxyl radical was able to oxidize a-TOH. 

Table 2 Contents of Hydroxycinnamic Derivatives in Ripe Fruits ... 

Figure 3 Chemical structure of some complex hydroxycinnamic derivatives identified in fruits and vegetables.

A sxunmary of the levels of hydroxycinnamate derivatives and other components among the hydroxycinnamate-containing ihiits and vegetables is presented in Table 8. Chlorogenie acid was identified as one of the major phenolic components in pear, apple, tomato, and peach/nectarine by Proteggente... 

Romani, A., Vignolini, P., Isolani, L., leri, F., and Heimler, D. 2006. HPLC-DAD/MS characterization of flavonoids and hydroxycinnamic derivatives in turnip tops (Brassica rapa L. sub-sp. sylvestris L.). Journal of Agricultural and Food Chemistry. 54(4), 1342-6. doi 10.1021/ jf052629x. 

Crude also contains 0.5% rosmarinic acid and total hydroxycinnamic derivatives at... 

Verbacoside, a hydroxycinnamic derivative present both in olive leaves and in alpemjo, exhibits moderate cytotoxic and cytostatic activity against skin mmors by inhibiting protein kinase C activity [240,241] and decreases the tumorigenicity of human gastric adenocarcinoma by 75% [242]. This compound has been used to repair brain oxidative damage caused by heroin consumption [243]. 

Figure 7.24 Hydroxycinnamate derivatives and flavonoids found in apples. Pears have a similar phenolic profile but do not contain phloretin conjugates while arbutin does not occur in apples.

Coumarin, the lactone of o-hydroxycinnamic acid, and some of its derivatives have been isolated from many plant species 31). Thimann and Bonner 141) attributed the growth-inhibiting effects of coumarin to its action on enzyme sulfhydryl groups. Inhibitory effects of coumarin on Avena coleoptiles and pea stem sections could be overcome by 2,3-dimercaptopropanol (BAL). Coumarin has also been reported to disrupt mitosis 29,30). 

The course of the reaction has not been fully clarified. Hydrolytic and aromatization processes are probably responsible for the formation of colored or fluorescent deriva4 tives (cf. Potassium Hydroxide Reagent). For instance, sevin is converted to a-naphthalkali metal salt of the o-hydroxycinnamic acid pro- duced by hydrolytic cleavage of the pyrone ring is converted from the non-fluorescent cis- to the fluorescent trans-form by the action of long-wavelength UV light (X = 365 nm) [2]. 

When the substituent groups in the polyphosphazenes were azobenzene [719] or spiropyran [720] derivatives, photochromic polymers were obtained, showing reversible light-induced trans-cis isomerization or merocyanine formation, respectively. Only photocrosslinking processes by [2+2] photo-addition reactions to cyclobutane rings could be observed when the substituent groups on the phosphazene backbone were 4-hydroxycinnamates [721-723] or 4-hydroxychalcones [722-724]. 

Takahama, U. Oxidation of hydroxycinnamic acid and hydroxycinnamyl alcohol derivatives by laccase and peroxidase—interactions among p-hydroxyphenyl, guaiacyl and syringyl groups during the oxidation reactions. Physiol. Plantarum 1995, 93, 61-68. 

Takahama, U. Oniki, T. Effects of ascorbate on the oxidation of derivatives of hydroxycinnamic acid and the mechanism of oxidation of sinapic acid by cell wall-bound peroxidases. Plant Cell Physiol. 1994, 35, 593-600. 

Murata, M., Okada, H., Homma, S., Hydroxycinnamic acid derivatives and p coumaryl-(L)-tryptophan, a novel hydroxycinnamic acid derivative from coffee beans, Biosci. Biotechnol. Biochem., 59(10), 1887, 1995. (CA124 54202q)... 

Hydroxycinnamic acids and their derivatives (free, soluble conjugated, cell wall bound)... 

The most common hydroxycinnamic acid derivatives are p-coumaric (4-hydroxy-cinnamic), caffeic (3,4-dyhydroxycinnamic), ferulic (4-hydroxy-3-methoxycinnamic), and sinapic (4-hydroxy-3,5-dimethoxycinnamic) acids, which frequently occur in foods as simple esters with quinic acid or glucose (Mattila and Kumpulainen 2002). 

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