Specific phenolic compounds

MnP is the most commonly widespread of the class II peroxidases [72, 73], It catalyzes a PLC -dependent oxidation of Mn2+ to Mn3+. The catalytic cycle is initiated by binding of H2O2 or an organic peroxide to the native ferric enzyme and formation of an iron-peroxide complex the Mn3+ ions finally produced after subsequent electron transfers are stabilized via chelation with organic acids like oxalate, malonate, malate, tartrate or lactate [74], The chelates of Mn3+ with carboxylic acids cause one-electron oxidation of various substrates thus, chelates and carboxylic acids can react with each other to form alkyl radicals, which after several reactions result in the production of other radicals. These final radicals are the source of autocataly tic ally produced peroxides and are used by MnP in the absence of H2O2. The versatile oxidative capacity of MnP is apparently due to the chelated Mn3+ ions, which act as diffusible redox-mediator and attacking, non-specifically, phenolic compounds such as biopolymers, milled wood, humic substances and several xenobiotics [72, 75, 76]. 

Specific Phenolic Compounds in Gossypium hirsutum L." M.S. Thesis, U. of Arkansas. 

Djordjevic MA, Redmond JW, Batley M, Rolfe BG. 1987. Clovers secrete specific phenolic compounds which either stimulate or repress nod gene expression in Rhizobium trifolii. EMBO J 6 1173-1179. 

The breakdown of furan aldehydes leads to the formation of formic and levulinic acid. Moreover, acetic acid is formed during the degradation of hemicellulose. Partial breakdown of lignin can generate a variety of phenolic compounds (23), which also inhibit S. cerevisiae (14,15). In contrast to furan aldehydes and aliphatic acids, the toxic effect of specific phenolic compounds is highly variable (15). Different raw materials and different approaches to prepare lignocellulose hydrolysates will result in different concentrations of the fermentation inhibitors (16,17). 

The steam pyrolysis of kraft black liquor to yield specific phenolic compounds by thermal decomposition. 

Specific Phenolic Compounds. The concentrations of caffeic and caftaric acids (hydroxycinnamates), and gallic acid (a benzoic acid) did not significantly differ from the control wine by the use of any of the fining agents at any of the levels tested. 

Other environmental applications are restricted to specific phenolic compounds included on the priority pollutant lists of the EU and USEPA, as is the case with the nitrophenolic isomers 2-nitrophenol, 4-nitrophenol, and the 2,4-dinitrophenol [190-192],... 

Figure 5.6. Dynamics of ergosterol litter content (solid lines) and phenolic index (dashed lines) over the course of decomposition (means and SD). Inset change in two specific phenolic compound litter contents (caffeic and p-coumaric acid) during decomposition In the three successlonal stage plots [CHO 14]...

One of the most recurrent case studies for the demonstration of the operation and possibilities offered by BioET is that of the determination of phenolic compounds, by phenol-degrading enzymes tyrosinase and laccase. Departing from these measurements, there can be developed different applications (1) to perform the iden-tification/classification of types of samples, (2) to estimate general indexes and (3) to resolve the presence of specific phenolic compounds. And many different specific applications can be developed to estimate polyphenolic compounds in wine, beer, juices, teas, coffee, fruits, etc., or to estimate polluting load in wastes originated in this type of industries. 

S A wastewater stream has a flowrate of 22 m /hr and contains 26.0 ppm of monochloro-phenol (MCP) and 3.0 ppm of trichlorophenol (TCP). Both phenolic compounds are toxic and must be reduced to acceptable levels prior to discharge. Design a cost-effective RON that satisfies the following specifications ... 

Some phenolic acids such as ellagic acid can be used as floral markers of heather honey (Cherchi et al., 1994 Ferreres et al., 1996a,b), and the hydroxyciimamates (caffeic, p-coumaric, and ferulic acids) as floral markers of chestnut honey (Cherchi et al., 1994). Pinocembrin, pinobanksin, and chrysin are the characteristic flavonoids of propolis, and these flavo-noid compounds have been found in most European honey samples (Tomas-Barberan et al., 2001). However, for lavender and acacia honeys, no specific phenolic compoimds could be used as suitable floral markers (Tomas-Barberan et al., 2001). Other potential phytochemical markers like abscisic acid may become floral markers in heather honey (Cherchi et al., 1994). Abscisic acid was also detected in rapeseed, lime, and acacia honey samples (Tomas-Barberan et al., 2001). Snow and Manley-Harris (2004) studied antimicrobial activity of phenolics. 

Inoue, K., Murayama, S., Seshimo, F., Takeba, K., Yoshimura, Y., and Nakazawa, H. (2005). Identification of phenolic compound in manuka honey as specific superoxide anion radical scavenger using electron spin resonance (ESR) and liquid chromatography with coulometric array detection. /. Sci. Food Agric. 85, 872-878. 

The LC-MS/MS technique has been used to quantify and identify phenolic compounds. In order to quantify, multiple reaction monitoring (MRM), in which there is a combination of the precursor ion and one of its daughter fragments, is used to characterize a particular compound. This behavior should be as specific as possible in samples with a complex mixture of phenolic compounds. This technique has been largely used to quantify phenolic compound metabolites in urine and plasma (Urpf-Sarda and others 2005, 2007). In this context, LC-ESI-MS/MS with negative mode has been applied for the identification of a variety of phenolic compounds in a cocoa sample (Sanchez-Rabaneda and others 2003 Andres-Lacucva and others 2000). 

A number of spectrophotometric methods for the quantification of phenolic compounds in plant materials have been developed. Based on different principles, these assays are used to determine various structural groups present in phenolic compounds. Spectrophotometric methods may quantify all extractable phenolics as a group (Marshall and others 2008), or they may determine a specific phenolic substance such as sinapine (Ismail and Eskin 1979) or a given class of phenolics such as phenolic acids (Brune and others 1989). 

By careful choice of both the reaction conditions and the phenolic compound used, it may be possible to produce a colour that is characteristic of a particular carbohydrate or related group, so giving some degree of specificity to the method. Thus, Seliwanoff s test uses hydrochloric acid and either resorcinol or 3-indolylacetic acid to measure fructose with minimal interference from glucose. The colour produced by pentoses with orcinol (Bial s reagent) or p-bromoaniline is sufficiently different from that produced by hexoses to permit their quantitation in the presence of hexoses. However, none of the methods based on the formation of furfural or its derivatives can be considered to be entirely specific. 

Until recently, most of the chemical research on the contents of these structures was directed at the identification of the constituents of castoreum. In the late 1940s Lederer [72, 73] identified 36 compounds and some other incompletely characterized constituents in castoreum of uncertain origin. Other constituents were subsequently identified in the material [74-77]. In a reinvestigation aimed specifically at the phenol content of the material, Tang et al [69] identified 10 previously unreported phenols in the castoreum from the North American beaver, Castor canadensis. Of the 15 phenols reported elsewhere, only five were confirmed in this analysis, in addition to 10 phenolic compounds that were not reported elsewhere. It was concluded that the 10 previously identified phenols that were not found in the study by Tang et al. were either absent or were not volatile enough to be detected by the methods employed. This was most probably because a relatively low maximum column temperature of only 210 °C was employed in the GC-MS analyses. The compounds identified by Lederer,... 

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