Distribution of phenolic acids

Zhou, Z., Robards, K., HelliweU, S., and Blanchard, C., The distribution of phenolic acids in rice. Food... 

Wang, B.-N., Liu, H.F., Zheng, J.B. et al. (2011) Distribution of phenolic acids in different tissues of jujube and their antioxidant activity. J. Agric. Food Chem., 59, 1288-1292. 

Microbial decomposition of phenolic acids Retention in the soil by sorption and polymerisation Amounts and distribution of phenolic acids in soils... 

Amounts and distribution of phenolic acids in soils As indicated above, the amounts of the phenolic acids extracted from soils are very dependent on the pH of the extractant. However it is of interest to examine the amounts extracted (a) by water and (b) by alkali at pH 13-14. 

X. Distribution of phenolic acids in soils of greenhouses and fields. Soil Science and Plant Nutrition, 25, 591-600. SHINDO H., OHTA S. and KUWATSUKA S. 1978. Behavior of phenolic substances in the decaying process of plants. 

IX. Distribution of phenolic acids in soils of paddy soils and forests. Soil Science and Plant Nutrition,... 

A third possibility is that mineral ions leak out of tissue in the presence of phenolic acids, not because membrane permeability is altered, but rather because the driving force that maintains high ion concentrations in cells (i.e. PD) is dissipated by the chemicals. Without an electrical potential, ions would distribute solely according to their chemical concentrations. Thus, most ions would leak out of cells to reach chemical equilibrium with the external environment. 

There are two categories of tannins condensed and hydrolyzable tannins. The polymerization of flavonoid molecules produces condensed tannins, which are commonly found in woody plants (Fig. 3.9). Hydrolyzable tannins are also polymers, but they are a more heterogeneous mixture of phenolic acids (especially gallic acid) and simple sugars. Though widely distributed, their highest concentration is in the bark and galls of oaks. 

The cited observations suggest that it is possible to identify potato cultivars with low or high phenolic acid content for human use and to select processing conditions that minimize losses of phenolic compounds. In summary, the methods we developed and used to determine the content and distribution of phenolic compounds in potato plant flowers, leaves, and tubers, in the peel and flesh parts of potato tubers, and in freeze-dried and processed commercial potatoes merit application in numerous studies designed to assess the role of potato phenolic compounds in host-plant resistance, plant breeding, plant molecular biology, food chemistry, nutrition, and medicine. The described wide distribution of phenolic compounds in different commercial... 

When hypofluorous acid reacts with aromatic substrates 7 the isomeric distribution of phenols formed suggests the nature of the transformation is electrophilic, rather than radical 4-methoxy(2-2H)phenol (8) isolated from (4-2H)anisole shows a marked NIH effect (77% incorporation of deuterium).11 A similar reaction with naphthalene gives a mixture of up to three products in low yield (1-naphthol 2.9%, 2-naphthol 0.75% and 1.4-naphthoquinone 7.4%).9... 

Polyphenolic phytochemicals are classified into three major groups phenolic acids, fla-vonoids, and tannins. Phenolic acids include hydroxybenzoic, hydroxyphenylacetic, and hydroxycinnamic acids (Figure 11.3.3). Hy-droxycinnamic acids are the most widely distributed of the phenolic acids in plant tissues. The important hydroxycinnamic acids are p-coumaric, caffeic, ferulic, and sinapic acids. Most hydroxycinnamic acids are rarely encountered in the free state in nature. They occur as glucose esters and, more frequently, as quinic acid esters (Herrmann, 1989). Phenolic acids are usually detected at wavelengths between 210 and 320 nm. In general, the polarity of phenolic acids is increased mainly by the hy-... 

Since the actual or potential phytotoxicity of a phenolic acid is determined by its physical and chemical properties and the susceptibility of the plant process involved, the actual or potential phytotoxicity of a given phenolic acid is best determined in nutrient culture in the absence of soil processes. The phytotoxicity observed in soil systems represents a realized or observed phytotoxicity, not the actual phytotoxicity, of a given phenolic acid. For example, the actual relative phytotoxicities (or potencies) for cucumber seedling leaf expansion were 1 for ferulic acid, 0.86 for p-coumaric acid, 0.74 for vanillic acid, 0.68 for sinapic acid, 0.67 for syringic acid, 0.65 for caffeic acid, 0.5 for p-hydroxybenzoic acid and 0.35 for protocatechuic acid in a pH 5.8 nutrient culture.5 In Portsmouth Bt-horizon soil (Typic Umbraquaalts, fine loamy, mixed, thermic pH 5.2), they were 1, 0.67, 0.67, 0.7, 0.59, 0.38, 0.35, and 0.13, respectively.19 The differences in phytotoxicity of the individual phenolic acids for nutrient culture and Portsmouth soil bioassays were due to various soil processes listed in the next paragraph and reduced contact (e.g., distribution and movement)36 of phenolic acids with roots in soils. 

Solid-probe mass spectrometric analysis (31) showed that the benzene-ether extracts consist mainly of organic acids. Therefore, these extracts were deriva-tized with dimethylsulfate-de to yield methyl-da-labeled derivatives. The derivatives were analyzed by GCMS and high resolution MS using techniques that have been described previously (31). Authentic samples of phenolic acids deriva-tized with dimethylsulfate-dg or diazomethane were also analyzed by GCMS for reference. The distribution of the organic acids as methyl esters was determined by measuring areas of GC fiame ionization detector peaks with a correction for the effective carbon number for each compound. 

Microspectrofluorometry was employed for mapping the location of phenolic substances in maize kernels. Autofluorescence due to phenolic acids was detected mainly in the embryo, aleurone and pericarp of maize kernel cross sections. Boric acid (H3BO3) reagent enhanced the fluorescence due to flavonoids in the aleurone layer. The amides of phenolic acids required derivatization with Ehrlich s reagent (168) to reveal fluorescence in the embryo and aleurone. The localization of phenolic amines was conflrmed by HPLC analysis. Phenolic compounds are important in the resistance of maize kernels to pests. Resistant maize types showed higher intensities of phenolic fluorescence but no unusual distributions of these compounds. ... 

Phenolic acids are found predominantly and widely distributed in almost all fruits. There are two classes of phenolic acids derivatives of benzoic acid... 

Phenolic acids and coumarins Two families of phenolic acids are widely distributed in plants - a range of substituted benzoic (Cg-Ci) acid derivatives and those derived from cinnamic (C -C ) acid. Both types of phenolic acids usually occur in conjugated or esterified form. The simpler types of benzoic acid derivatives include p-hydroxybenzoic, protocatechuic, vannilic, gallic and syringic acids, and the o-hydroxy salicylic and gentisic acids (Fig. 1). The cinnamic acids p-coumaric, caffeic, ferulic, and sinapic, are found in most oilseeds and occur frequently in the form of esters with quinic acid or sugars (Fig. 1). Chlorogenic... 

Phenolics are an important class of natural products that have received immense interest for their remarkable biological activities. These are widely distributed in the plant kingdom. Nowadays, increasing attention is paid on rapid identification and characterization of phenolic acids from natural sources. This chapter particularly emphasizes on the diverse mass spectrometric application for the detection of phenolic acids, and several aspects related to fragmentation behavior of phenolic acids are discussed. 

Historically, simple phenolic acids have been the most frequently identified allelopathic agents (see literature reviews by Rice 1974, 1979, 1983, 1984, 1986). One would assume this was partly because of the fact that the necessary technology to isolate, identify, and quantify phenolic acids, even though crude in the early days, was readily available to most researchers. Furthermore, simple phenolic acids, such as the benzoic acid and cinnamic acid derivatives serve a variety of plant and ecosystem functions and are widespread in higher plants (Fig. 2.4 Bates-Smith 1956 Harborne 1982,1990 Goodwin and Mercer 1983 Siqueira et al. 1991). The ubiquitous distribution in nature and their apparent rapid turnover rates in soils, however, have lead to some controversy as to the importance of phenolic acids in plant-plant allelopathic interactions (Schmidt 1988 Schmidt and Ley 1999 Blum 2004, 2006). Finally, the behavior of phenolic acids in soil systems are somewhat similar to the behavior of a whole host of other organic acids (e.g., acetic acid, butyric acid, citric acid, formic acid, fiimaric acid, lactic acid, malonic acid, tannic acids and tartaric... 

In summary the rate of depletion (i.e., root uptake and microbial utilization) varies with type phenolic acid present, concentration, pH, time of day, time of day of treatment, number of treatments, composition of phenolic acid mixtures, whether uptake is apoplastic or symplastic, phenolic acid-utilizing microbial populations present on roots and in the nutrient solution, and aeration. Phenolic acid treatments of seedlings in nutrient culture modify microbial populations on root surfaces (rhi-zoplane) and in the nutrient solutions. Once taken up by roots, phenolic acids were distributed throughout seedlings. Highest concentrations, however, were retained in the roots. 

The higher concentrations of phenolic acids required for a given percent inhibition between the two systems stem from the fact that nutrient cultures have a much more consistent environment than soil culture systems in that water, nutrients, and phenolic acids are evenly distributed in the treatment container and thus are readily available to interact with root surfaces. Soil systems, on the other hand, are much more complex heterogeneous environments in which roots must compete with a variety of soil sinks (e.g., clays, organic matter, and microbes) for water, nutrients, and phenolic acids. There is also mechanical resistance to the movement of water, nutrients, and phenolic acids and the growth of roots in soils. The slower development of inhibition after treatment and the slower recovery after phenolic acid depletion in soil systems is very likely related to the slower growth of seedlings in soil culture. 

Qualitative and quantitative determinations of phenolie acids, especially the combined forms, have been significantly improved during the last two decades, allowing one to draw a general picture of their distribution in fruits and vegetables and flieir importance as food constituents. In the comprehensive reviews on these topics that have already been pubUshed [1-5] most of the oldest references may be found. In the present review, our attention is focused on the presence and content of phenolic acids in fruits (mainly fleshy fruits with then-seeds) and vegetables, and on the main parameters fliat can modify them. 

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