Phenolic compounds, influence

Silva, L, Campos, F.M., Hogg, T, and Couto, J.A. (2011) Wine phenolic compounds influence the production of volatile phenols by wine-related lactic acid bacteria. 7 App/ Microbiol 111, 360-370. 

The type of catalyst influences the rate and reaction mechanism. Reactions catalyzed with both monovalent and divalent metal hydroxides, KOH, NaOH, LiOH and Ba(OH)2, Ca(OH)2, and Mg(OH)2, showed that both valence and ionic radius of hydrated cations affect the formation rate and final concentrations of various reaction intermediates and products.61 For the same valence, a linear relationship was observed between the formaldehyde disappearance rate and ionic radius of hydrated cations where larger cation radii gave rise to higher rate constants. In addition, irrespective of the ionic radii, divalent cations lead to faster formaldehyde disappearance rates titan monovalent cations. For the proposed mechanism where an intermediate chelate participates in the reaction (Fig. 7.30), an increase in positive charge density in smaller cations was suggested to improve the stability of the chelate complex and, therefore, decrease the rate of the reaction. The radii and valence also affect the formation and disappearance of various hydrox-ymethylated phenolic compounds which dictate the composition of final products. 

Nutrient deficiencies may also influence the production of allelochemics. The compounds studied in great detail have been the phenolic compounds and scopolin-related chemicals. Deficiencies of boron, calcium, magnesium, nitrogen, phosphorus, potassium, and sulfur have all been reported to enhance the concentration of chlorogenic acids and scopolin in a variety of plants (4). In other species, chlorogenic acids have decreased in plants that are deficient in magnesium or potassium. 

Many herbicides and other chemicals have been reported to influence levels of various phenolic compounds in higher plants by unknown mechanisms. It is unlikely that more than a few of these compounds have a primary influence on secondary phenolic compound synthesis. For instance, in our survey of the effects of 17 herbicides on anthocyanin accumulation, only glyphosate appeared to directly influence accumulation (31). The effects of several compounds on secondary phenolic compound production for which the mechanism of influence is unknown are summarized in Table II. A much longer list could be derived from the literature. Unfortunately, many of these compounds are phytotoxic or are known to have effects other than on secondary aromatic compound production. In most cases the effects on these compounds correlate well with extractable PAL activity (31, 71, 72, 73, 74) (Figure 5), even though they do not directly affect the enzyme. 

Since lignins are polymers of phenolics and are major plant constituents with resistance to microbial decomposition, they are the primary source of phenolic units for humic acid synthesis (178, 179). Once transformed, these humic acids become further resistant to microbial attack and can become bound to soils (180) form interactions with other high molecular weight phenolic compounds (ex. lignins, fulvic acids) and with clays (181) and influence the biodegradation of other organic substrates in soils (182, 183). 

Fresh peppers are excellent sources of vitamins A and C, as well as neutral and acidic phenolic compounds (Howard and others 2000). Levels of these can vary by genotype and maturity and are influenced by growing conditions and processing (Mejia and others 1988 Howard and others 1994 Lee and others 1995 Daood and others 1996 Simmone and others 1997 Osuna-Garcia and others 1998 Markus and others 1999 Howard and others 2000). Peppers have been reported to be rich in the provitamin A carotenoids (3-carotene, a-carotene, and (3-cryptoxanthin (Minguez-Mosquera and Hornero-Mendez 1994 Markus and others 1999), as well as xanthophylls (Davies and others 1970 Markus and others 1999). Bell peppers have been shown to exert low antioxidant activity (Al-Saikhan and others 1995 Cao and others 1996 Vinson and others 1998) or may even act as pro-oxidants (Gazzani and others 1998). 

Various analyzers have been used to analyze phenolic compounds. The choice of the MS analyzer is influenced by the main objective of the study. The triple quadrupole (QqQ) has been used to quantify, applying multiple reaction monitoring experiments, whereas the ion trap has been used for both identification and structure elucidation of phenolic compounds. Moreover, time-of-flight (TOF) and Fourier-transform ion cyclotron resonance (FT-ICR) are mainly recommended for studies focused on obtaining accurate mass measurements with errors below 5 ppm and sub-ppm errors, respectively (Werner and others 2008). Nowadays, hybrid equipment also exists, including different ionization sources with different analyzers, for instance electrospray or atmospheric pressure chemical ionization with triple quadrupole and time-of-flight (Waridel and others 2001). 

Virgin olive oil contains considerable amounts of simple phenols that have a great effect on the stability/sensory and nutritional characteristics of the product. Some of the most representative are hydroxytyrosol (3,4-dihydroxyphenylethanol) and tyrosol (4-hydroxyphenylethanol) however, phenolic compounds are removed when the oil is refined (Tovar and others 2001). The phenolic content of virgin olive oil is influenced by the variety, location, degree of ripeness, and type of oil extraction procedure used, and that is why hydroxytyrosol can be considered as an indicator of maturation for olives (Esti and others 1998). Hydroxytyrosol concentrations are correlated with the stability of the oil, whereas those of tyrosol are not (Visioli and Galli 1998). 

On the other hand, allelopathic effect was negatively influenced by rainfall (Shiming 2005). The inhibition process was mitigated by shading and consequent moisture conservation (Muller 1966). Allelopathic activity can vary as well with photoperiod (Peng et al. 2004). Harder et al. (1998) found out that an increasing availability of nutrients decreased the concentration of allelopathic effective phenolic compounds in the plants of two winter wheat varieties. In soil, allelochemicals can be adsorbed by soil particles, decomposed by microorganisms and move with water. 

Roberts, J.R., DeFrietas, A.S.W., and Bidney, M.A.J. Influence of lipid pool size on bioaccumulation of the insecticide chlordane by northern redhorse suckers (Maxostoma macrolepidotimij, J. Fish. Res. Board Can., 34(l) 89-97, 1977. Roberts, M.S., Anderson, R.A., and Swarbrick, J. Permeability of human epidermis to phenolic compounds, /. Pharm. Pharmaa, 29 677-683, 1977. 

Bosso, A., Guaita, M., Vaudano, E., and Di Stefano, R. (2000). Influence of oxygen on the evolution of phenolic compounds during red wine aging. Ind. Bevande 29, 630-640. 

El-Morsi, E. A., Abdel-Naem, G. R, Shaker, E. S., Ghazy, M. A. (2000). Influence of biofertilization on total phenolic compounds and antioxidative activity of potato tubers (Solanum tuberosum L.). Arab Univ J Agric Sci,8, 1-18. 

Table 6.5 shows the distribution of the three phenolies in the peel and flesh ofthe Korean Superior potato variety available in four sizes large, medium, small, and very small. The data indicate that the size of the potato does not seem to influence the total phenolic content, except that the ratio of peel to flesh for the very small potatoes (7.95) is about one half the corresponding ratios of the other three potatoes. These results indicate that the distribution of phenolic compounds between peel and flesh varies widely among different potato varieties. They also suggest that... 

Table XII. Influence of Yeast Cells on the Phenolic Compound Content of a Synthetic Medium...

Phenolic compounds are of interest due to their potential contribution to the taste (astrin-gency, bitterness, and sourness) and formation of off-flavor in foods, including tea, coffee, and various fruit juices, during storage. Their influence on the appearance of food products, such as haze formation and discoloration associated with browning in apple and grape products, is also significant. Furthermore, analysis of these phenolic compounds can permit taxonomic classification of the source of foods. The importance of each phenolic compound and its association with the quality of various foods is described further in Sec. IV, on food applications. 

Also, the phenolic compounds in olives have a strong influence on the flavor of the oil and seem to be responsible for the high oxidation resistance of olive oil. The phenolic content in the flesh of olive fruits ranges between 1% and 3%, w/w, (66) oleuropein, vanillic, caffeic, p-coumaric acid, rutin, luteolin-7-glucoside, heterosidic ester of caffeic acid, and hydroxytyrosol (verbascoside) have been identified in olive fruits. 

In addition to influencing the rate of a reaction, pH may also control the products where alternate or sequential pH-dependent reactions take place. An example of this type of reaction is the chlorination of phenol. Lee and Morris (37) have shown that the chlorination of phenol proceeds by the stepwise substitution at the 2, 4, and 6 positions of the aromatic ring. The rate of each of these reactions depends on the product of phenate or chlorophenate anion and the hypochlorous acid concentrations. Since each phenolic compound has a slightly different acid dissociation constant, the species of chlorophenols that are formed depend on the pH of the solution. 

Furfural is a resin former under the influence of strong acid. It will self-resinify as well as form copolymer resins with furfuryl alcohol, phenolic compounds, or convertible resins of these. Conditions of polymerization, whether aqueous or anhydrous, inert or oxygen atmosphere, all affect the composition of the polymer. Numerous patents have issued relating to polymerization and to applications. Although the resins exhibit a degree of britdeness, they have many outstanding properties a number of applications are discussed under MUses.M... 

Aside from vitamins C and E many other compounds present in fruits and vegetables have been shown to have anti-oxidant properties. Among these compounds there are several classes of phenolic compounds. Aside from preventing scurvy these compounds have a positive influence on cardiovascular health. 

Polyphenylenoxide (PPO) Substituted phenols are used as monomers for the production of polyphenylenoxides, (PPOs) so they as well as phenolic degradation products can be found as emitted odor active compounds. In one case the odor of a PPO was predominantly caused by 2,6-dimethylphenol and trimethylanisol as well as by a tentatively identified substituted methoxypyrazine (Mayer and Breuer, 2004a). Another potent odorant derived from higher molecular phenolic compounds, antioxidants for example, by the influence of heat (>200 °C) and pressure is guaiacol (2-methoxyphenol) (Mayer and Breuer, 2006). 

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