Phenolic acids chemical structure

Fig. 3.38.The IUPAC names of Sudan azo dyes are as follows Sudan 1 = 1— [(2,4-dimethylphenyl)azo]-2-naphtalenol Sudan II = l-(phenylazo)-2-naphtol Sudan III = l-(4-phenylazophenylazo)-2-naphtol Sudan IV = o-tolyazo-o-tolyazo-beta-naphtol and Disperse Orange 13 = 4-[4-(phenylazo)-l-naphtylazo]-phenol. Azo dyes were separated in an ODS column (250 x 2.1 mm i.d. particle size 5 /xm) at 35°C. The isocratic mobile phase consisted of 0.1 per cent formic acid in methanol-0.1 per cent formic acid in water (97 3, v/v). The flow rate was 200 /xl/min. MS conditions were nebulizing and desolvation gas were nitrogen at the flow rates of 50 and 5551/h, respectively electrospray voltage, 3.0 kV cone voltage 25 V source temperature, 110°C desolvation temperature, 110°C. Azo dyes were extracted from the samples by homogenizing 1 g of sample with 10 ml of acetone, then the suspension was centrifuged and an aliquot of 3 ml of supernatant was mixed with 1 ml of deionized water, filtered and used for analysis. LC-ESI-MS/Ms SRM traces of standards and spiked samples are listed in Fig. 3.39. It was found that the detection and quantitation limits depended on both the chemical structure of the dye and the character of the accompanying matrix. LOD and LOQ values in chilli tomato sauce...

To elucidate some enzymatic characteristics of the isolated laccases I, II, and III, substrate specificities for several simple phenols, electrophoresis patterns, ultraviolet spectra, electron spin resonance spectra, copper content, and immunological similarities were investigated. Tyrosine, tannic acid, g c acid, hydroquinone, catechol, pyrogallol, p-cresol, homocatechol, a-naphthol, -naphthol, p-phenylenediamine, and p-benzoquinone as substrates. No differences in the specificities of these substrates was found. The UV spectra for the laccases under stucfy are shown in Figure 4. Laccase III displays three adsorption bands (280, 405, and 600nm), laccase II shows one band 280nm), and laccase I shows two bands (280 and 405 nm). These data appear to indicate differences in chemical structure. The results of the copper content analysis (10) and two-dimensional electrophoresis also indicate that these fractions are completely different proteins (10), Therefore, we may expect differences in substrate specificities between the three laccase fractions for more lignin-like substrates, yet no difference for some simple phenolic substrates. 

Polyphenols constitute one of the most and widely distributed groups of substances in the plant kingdom, with more than 8000 phenolic structures currently known. They can be divided into at least 10 different classes based upon their chemical structure, ranging from simple molecules, such as phenolic acids, to highly polymerized compounds, such as tannins. 

Polyphenols can act as antioxidants by a number of potential pathways. The most important is likely to be by free radical scavenging, in which the polyphenol can break the radical chain reaction. Polyphenols are effective antioxidants in a wide range of chemical oxidation systems, being capable of scavenging peroxyl radicals, alkyl peroxyl radicals, superoxide, hydroxyl radicals, nitric oxide and peroxynitrate in aqueous and organic environments [121]. This activity is due to the ability of donating an H atom from an aromatic hydroxyl group to a free radical, and the major ability of an aromatic structure to support an unpaired electron by delocalization around the 7i-electron system. Phenolic acids... 

We conclude our short discussion of relationships between chemical structure and light absorbance by considering some cases in which an acid or base function forms part of a chromophore. Important examples of compounds exhibiting such chro-mophores are phenols and anilines. As is evident from the spectra shown in Fig. 15.5, deprotonation of a phenolic group results in a substantial bathochromic shift... 

After benzoylation, it was possible to analyze together the food substances of varying chemical structures, such as alcohols, esters of 4-hydroxybenzoic acid, phenolic antioxidants, saccharides, and sugar alcohols. The method allowed the determination of these substances in different matrices by the same analytical procedure, using the same cleanup. The preservatives were separated on an RP-18 column. Acetonitrile-water (50 35) or acetonitrile-water-butylmethyl ether (110 35 40) were used as mobile phases. Detection was UV at 230 nm (71). 

Based on their chemical structure, the organic chemicals were divided into a number of categories alkanes, alkenes, amines, aromatic hydrocarbons, benzenes, carboxylic acids, halides, phenols, and sulfonic acid. Linear regression analysis has been applied using the method of least-squares fit. Each correlation required at least three datapoints, and the parameters chosen were important to ensure comparable experimental conditions. Most vital parameters in normalizing oxidation rate constants for QSAR analysis are the overall liquid volume used in the treatment system, the source of UV light, reactor type, specific data on substrate concentration, temperature, and pH of the solution during the experiment. 

Figure 2.2 Chemical structure of phenolic acids. Phenolic acids commonly found with two substitutions on the (a) phenyl ring on the 3- and 4-positions and (b) some less commonly found with triple substitutions on the 3-, 4-, and 5-positions.

Numerous studies on the metabolism of 2,1t-dichlorophenoxy-acetic acid (2,1+-D) and related herbicides in animals have shown that these chemicals are absorbed and distributed rapidly in the body, and are excreted, undegraded, relatively quantitatively in the urine within a week after administration (M Pharmacokinetic studies with 2,1+,5-T in rats and dogs (5.) and in humans (6J supported these findings, and demonstrated that rates of clearance from plasma and elimination in urine depend on dosage level, animal species, and chemical structure of the phenoxy acid being studied ( + ). Corresponding chlorinated phenol metabolites were detected only in ruminants (M or in trace amounts in urine of rats fed very high doses of phenoxy herbicides (7.) ... 

The safety limit of temperature depends on the chemical structure of the compound being nitrated. For exMnple, in the nitration of dinitrotoluene to trinitrotoluene or of phenol to picric acid, temperatures neM 120°C Mid over are considered dangerous. In the nitration of dimethylaniline to tetiyl, a temperature higher than 80°C must be considered dangerous. Esterification with nitric acid should be carried out at a temperature close to room temperature or lower. 

Figure 3.1 Chemical structures of benzoic acid, cinnamic acid, and common phenolic acids.

Figure 16. Chemical structures of antioxidative phenolic acids.

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