Caffeic acid comparison

Except perhaps for caffeic acid (H.86), these acids were mainly identified after hydrolysis of extracts, which means after degradation of the chlorogenic acids, CGA (See Section 2.1.4). In commercial roasted coffee, Hughes and Thorpe (1987) identified, by comparison with standard compounds, coumaric acid (without specification, probably p-), isoferulic acid (H.88) but surprisingly not ferulic acid (H.87), caffeic acid (H.86) and its dimethyl ether (H.89) as well as sinapic acid (H.90). They used capillary GC for the separation and identification of these phenolic acids and other carboxylic acids. The cinnamic acids are generally linked to quinic acid, but in robusta coffee caffeic and /j-coumaric (H.84) acids have also been identified as derivatives of tryptophan (see Section 2.1.2) (Morishita et al., 1987 Murata et ah, 1995) and... 

The antioxidant effects of natural phenols in olive oils was studied by Papadopoulos [46], adding extracts of a VOQ, having polyphenols, to a sophisticated bleaching oil, washed-out of phenolic antioxidants and evidenced a significant inhibition of auto-oxidation over time in comparison with samples without such an addition. On the other hand, it has revealed that this effect is more pronounced in hydroxy-tyrosol than caffeic acid and protocatechuic acid... 

In general, the oxidation of linoleic acid was inhibited by the enzyme coupled antioxidant substrates even after a strong washing treatment (WCA and WCHG) in comparison with the control sample. The caffeic acid (CA) and chlorogenic acid (CHG) treated wool samples exhibited potent antioxidant activities with 75.12 % and 54.15 % inhibition of linoleic acid peroxidation, respectively. 

Fig. 3.8 Phenolic acids extracted from wheat stubble, wheat straw from half buried litter bags, and wheat stubble/soybean (no-till) soil. Phenolic acids isolated and quantified were caffeic acid (CAF), ferulic acid (FER), p-coumaric acid (PCO), p-hydroxybenzoic acid (POH), sinapic acid (SIN), syringic acid (SYR), and vanillic acid (VAN). Becausep-coumaric acid was so high in comparison to other phenolic acids in wheat residues, data are presented twice, once with p-coumaric acid (a) and once without p-coumaric acid (b). Because phenolic acids were so low in the soil they are also presented in (c). The absence of standard error bars for wheat straw and soil indicates that the error bars are too small to be visible. Figures based on data from Blum et al. (1991, 1992). Plenum Publishing Corporation, data used with permission of Springer Science and Business Media...

Purpurein (107), isolated from the bark of Salix purpurea, was established as a diastereomer of grandidentatin by comparison of the de-/ -coumaroylated purpurein with grandidentin, a product of alkali hydrolysis of grandidentatin (92). The absolute stereochemistry of these two coumaroyl esters of l,2-c/5-hexane diol remains to be solved. Grandidentoside (108), another cyclohexane diol glucoside isolated from R grandidentata, was determined to be a caffeic acid ester of the similar glucoside (34). 

Flow injection methodology was used to estimate the total phenolic content of wine using acidic potassium permanganate chemiluminescence detection by Costin et al. (2003). Simple phenolic compounds such as quercetin, rutin, catechin, epicatechin, ferulic acid, caffeic acid, gallic acid, 4-hydroxycinnamic acid, and vanillin were examined analytically with chemiluminescence. Analysis of 12 different wines showed that detection limits were 2 x 10 M for caffeic acid, 3 x 10 M for ferulic acid, and 5 x 10 M for gallic acid. Comparison of the results of the chemiluminescence methodology and other total phenol/antioxidant assays showed that their correlation was good. Chemiluminescence... 

Certain phenolic compounds, such as caffeic acid and P-coumaric acid, can determine the decomposition of Aleppo pine needles in secondary successions, with a slowdown in the colonization needles by decomposers in young pines, in comparison to older pines (Figure 5.6) due to longer residence time for phenolic compounds in pine needle litter. 

The four most abundant compounds in the root latex of the sweet potato roots were identified by comparison with standards synthesised in our laboratory as octadecyl and hexadecyl esters of caffeic and / -coumaric acids (1 - 4, Figure 2). The most abundant compounds in the latex of Tanzania were 2 and 4 with only a small amount of 1 in comparison to the amounts in New Kawogo (Figure 4). 

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