Phenols hydroxy cinnamic acids

Schultz, J. M., and K. Herrmann. Occurrence of hydrohybenzoic acid and hydroxy cinnamic acid in spices. IV. Phenolics of spices. Z Lebensm-Unters Forsch 1980 171 193-199. Hussein Ayoub, S. M., and A. Baerheim-Suendsen. Medicinal and aromatic plants in the Sudan usage and exploration. Fitoterapia 1981 52 243-246. 

Table 4 Gradient HPLC Analysis for Phenolic Acids, frans/cis-Hydroxy cinnamic Acids, Flavan-3-Ols, Flavonols, and Procyanidins...

Commercial pectolytic enzymes used in clarification can cause hydrolysis of hydroxy cinnamic acids in apple, pear and grape juice [183]. In addition, the use of gelatin as a fining agent reduces total phenolics with the polymeric phenolics being the most affected. 

Regarding phenolic acids, most compounds are commercially available and can thus be positively identified by comparison of their retention time and UV spectra with those of reference compounds. Hydroxy cinnamic acids absorb at two regions of the UV spectrum, presenting a maximum at 225-235 nm and two other, very near from each other, by 290-330 nm. The double absorption in this region arises from the presence of cis and trans isomers, and the ratio between these two forms contributes to the final spectrum. 

Vanbeneden N, Delvaux F, Delvaux FR (2006) Determination of hydroxy cinnamic acids and volatile phenols in wort and beer by isocratic high-performance liquid chromatography using electrochemical detection. J Chromatogr A 1136 237-242... 

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...

Other strains, like VLl, were selected for their low vinyl-phenol production. These compounds possess rather unpleasant pharmaceutical aromas. Above a certain concentration, they dull the aroma of dry white wines (Volume 2, Sections 8.4.2 and 8.4.3). These strains have low cinnamate decarboxylase activity. During alcoholic fermentation, this enzyme catalyzes the partial transformation of p-coumaric and ferulic acid found in juice into vinyl-4-phenol and vinyl-4-gaiacol. Since this enzyme is inhibited by phenolic compounds, only white wines can contain quantities of vinyl-phenols likely to affect their aroma. The use of strains with low cinnamate decarboxylase activity is recommended— particularly for white juices containing high concentrations of hydroxy cinnamic acid. 

The background and detailed mechanisms of decarboxylation are very extensive, and therefore this chapter will discuss some specihc pathways of decarboxylation. In addition, we have highlighted recent cases of decarboxylation relevant to hydroxy-cinnamic acids in wine, beer and camelina and attempted to reason if such strategies can be transferred for value addition to processing of rapeseed and canola. An update on the recent thermal decarboxylation to form canolol, a phenol of interest in rapeseed and canola processing, is discussed in the last part of this chapter. 

By total cinnamic acids A By total hydroxy cinnamic acids o By total phenolic compounds... 

The physiology of PAL production in plants has attracted much attention, partly because the control mechanism of PAL synthesis ultimately determines how much phenolic is produced at any one time in plant tissues. Engelsma has found that addition of Mn can increase PAL levels in plants, or at least in gherkin hypocotyls. A range of other metal ions was tested and the only other with any effect, a slight one, was Mg ". The effect of Mn is indirect, since it is presumably involved in removing from the site of synthesis hydroxy-cinnamic acids which normally accumulate and repress and/or inactivate PAL. 

This product has been isolated from marine sources. This metabolite was synthesized first in 1964 in Japan and discovered later on in 1991 in India as a natural product. Bose et al. (2004) further reported a new method for synthesis of 2-nitro-4-(2 -nitroethenyl)phenol from p-hydroxy cinnamic acid under microwave irradiation. 

Compound retention during RP-HPLC depends on the relative hydrophobicity of the sample compounds. As expected, the elution of phenolics for reversed-phase HPLC is in the order of decreasing polarity. Polarity is increased most by hydroxyls at the 4-position, followed by those at the 2- and 3-positions. Availability of the methoxy group and the acrylic substitution reduces polarity and increases retention times (4). Loss of polar hydroxy groups and/or addition of methoxy groups can decrease the polarity within each class of benzoic and cinnamic acid. Also, the presence of the ethylenic side chain in the cinnamic acids can reduce their polarity compared with similarly substituted benzoic acids (6). The elution order for benzoic acids is as follows (Table 1) gallic > a-resorcylic > protocatechuic > y-resorcylic > gentisic > p-hydroxyben-... 

Good-rite 3125 (hindered phenol) B. F. Goodrich Co. 3,5-Di-tert-butyl-4-hydroxyhydro-cinnamic acid triester with 1,3,5 -tris(2-hydroxy-ethyl)-s-triazine-2,4,6(1H,3U,5fl)-trione... 

Phenolic acids include the benzoic acids (Ce-Ci), e.g., gallic, vanillic, syringic, protocatechuic, p-hydroxy-benzoic acid, as well as cinnamic acids (C6-C3), e.g., caffeic, p-coumaric, ferulic, sinapic acids, and their dep-sides and derivates, e.g., rosmarinic acid and lithospermic acid (Fig. 1). Phenolic acids and flavonoids in plants may occur in the free form, but they are often glycosylated with various sugars, especially glucose. Phenolic acids may also be present in the esterified as well as bound forms. Free phenolic acids are found especially in herbs and spices and, very often, in compounds responsible for antioxidant activity (benzoic and cinnamic acids and some of their derivatives). The bound forms are more common for the fruits, vegetables, and other plant materials. Therefore, in some cases, it is necessary to combine the analysis of their free and bound forms. 

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