Phenolic acids,

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 

Norwood et al. (1980) chlorinated a considerable number of phenolic acids of both benzoic and cinnamic acid types and looked for haloform production. Concentrations were from 0.5-6 mM and approximately a twofold excess of chlorine was added. For most of the acids tested, except those with 1,3-dihydroxy (resorcinol-type) substituents, chloroform yields were low (0-4 7o) except in the case of 3-methoxy-4-hydroxycinnamic acid (ferulic acid, 10), where about an 11% yield was 

Unactivated aromatic rings such as benzene show little tendency to chlorinate under water treatment conditions. Biphenyl has been studied somewhat intensively because of concerns that polychlorinated biphenyls might form in wastewaters containing the parent compound, a common dye carrier particularly in the carpet industry. Wastewaters may contain this hydrocarbon at up to 2 mg/L (Gaffney, 

Biphenyl would not be expected to be very reactive toward electrophilic attack on empirical grounds, since the phenyl substituent has poor electron-donating characteristics (Table 1.3). In model aqueous chlorination practice, only under rather extreme conditions does even a monochlorobiphenyl isomer form, and these compounds were virtually inert to further substitution (Carlson and Caple, 1978 Snider and Alley, 1979). 

The main non-flavonoids of dietary significance are the Cs-Ci phenolic acids, most notably gallic acid, which is the precursor of hydrolysable tannins, the C6-C3 hydroxycinammates and their conjugated derivatives, and the polyphenolic C6-C2-C6 stilbenes (Table 1.1). 

It has been suggested that lack of tolerance to tannins may be one reason for the demise of the red squirrel. The grey squirrel is able to consume hazelnuts before they mature, and to survive on acorns. In contrast, the red squirrel has to wait until the hazelnuts are ripe before they become palatable, and it is much less able to survive on a diet of acorns which are the only thing left after the grey squirrels have eaten the immature hazelnuts (Haslam 1998). 

Rump [17] has described a cellulose thin layer method for the detection of phenolic acids such as m-hydroxybenzoic acid, m-hydroxyphenylacetic acid and wj-hydroxyphenylpropionic acid, in water samples suspected to 

The phenolic lipids occur in many different botanical families, notably in the Anacardiaceae, and they exist in tropical, sub-tropical, temperate climates in certain trees, shrubs and plants. In addition they are found in some bacterial and antibiotic sources and in certain insects. As benzenoid derivatives they are conveniently. although perhaps artificially, grouped for chemical purposes into phenolic acids, polyhydric, dihydric and monohydric phenols. Tables 13.1, 13.2 and 13.3 and the collections of formulae summarise some of the the information on these products. The structural types are extensive. For example, (5-phenylalkylphenols have been isolated from several different sources and included are certain bridged biphenyls from Grevillea and Betulaceae species. 

Cashew nut i.e. Anacardic acids (15 0)-Anacardic acid 1 2 Brazil, India 

Anacardic acids 2-Hydroxy-6-[(Z)-tridec-8-enyl]-, and (13 0),(15 0) 2-Hydroxy-6-[(Z)-pentadec-8-enyl]- 

BOTANICAL/ COMMON/ MAIN FORMULA STRUCT- REF. COUNTRY 

BIOLOGICAL NAME TRIVIAL NAME COMPONENT URE OF ORIGIN 

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Other Phenolic Compounds. There are several phenolic acids important to tea chemistry. GaUic acid (3) and its quinic acid ester, theogallin (4), have been identified in tea (17,18) and have been detected by hplc (19,20). 

Dissociation extraction is the process of using chemical reac tion to force a solute to transfer from one liquid phase to another. One example is the use of a sodium hydroxide solution to extract phenolics, acids, or mercaptans from a hydrocarbon stream. The opposite transfer can be forced by adding an acid to a sodium phenate stream to spring the phenolic back to a free phenol that can be extrac ted into an organic solvent. Similarly, primary, secondary, and tertiary amines can be protonated with a strong acid to transfer the amine into a water solution, for example, as an amine hydrochloride salt. Conversely, a strong base can be added to convert the amine salt back to free base, which can be extracted into a solvent. This procedure is quite common in pharmaceutical production. 

In general, this method is a one-step procedure for the oxidation of a cresol type of molecule to the corresponding phenolic acid. The vigorous reaction conditions clearly limit the type of functional groups that may be present in the molecule. There is no evidence that the reaction has been applied to polynuclear or heterocyclic alkylphenols. 

A comparison of phenol acidity in DMSO versus the gas phase also shows an attenuation of substituent effects, but not nearly as much as in water. Whereas the effect of ubstituents on AG for deprotonation in aqueous solution is about one-sixth that in the gas phase, the ratio for DMSO is about one-third. This result points to hydrogen bonding of the phenolate anion by water as the major difference in the solvating properties of water and DMSO. ... 

Phenol Acidic Dimethyl sulfoxide Bifunctional (leans basic)... 

Many applications of novolacs are found in the electronics industry. Examples include microchip module packaging, circuit board adhesives, and photoresists for microchip etching. These applications are very sensitive to trace metal contamination. Therefore the applicable novolacs have stringent metal-content specifications, often in the low ppb range. Low level restrictions may also be applied to free phenol, acid, moisture, and other monomers. There is often a strong interaction between the monomers and catalysts chosen and attainment of low metals levels. These requirements, in combination with the high temperature requirements mentioned above, often dictate special materials be used for reactor vessel construction. Whereas many resoles can be processed in mild steel reactors, novolacs require special alloys (e.g. Inconel ), titanium, or glass for contact surfaces. These materials are very expensive and most have associated maintenance problems as well. 

Various phenolic acids have been reported to inhibit IAA oxidase (9, 52,120), and other phenols may act as cofactors of IAA oxidase (144). In general, the cofactors of IAA oxidase are monophenols, whereas the inhibitors of the system are polyphenols, with o-dihy-droxyphenols being the most inhibitory (52, 65). Unsaturated lactones have also been reported to inhibit IAA oxidase (2, 52). 

Arabinoxylans with a substitution of the P-(l—>4)-D-xylopyranose backbone at position 2 or 3 with ArbF can be esterified partly with phenolic acids. This type is frequently found in the starchy endosperm and the outer layers of cereal grains. 

Many studies have been undertaken to establish the structural criteria for the activity of polyhydroxy flavonoids in enhancing the stability of fatty acid dispersions, lipids, oils, and LDL. " As for phenolic acids, the inhibition of oxidation by flavonoids is related to the chelation of metal ions via the... 

RicE-EVANS c A, MILLER N J and PANANGA G (1997) Strucmre-antioxidaut activity relationship of flavonoids and phenolic acids in Flavonoids in Health and Disease, 199-209 (Packer, L and Rice-Evans, C A, eds.) Marcel Dekker, New York. 

Knowledge of the identity of phenolic compounds in food facilitates the analysis and discussion of potential antioxidant effects. Thus studies of phenolic compounds as antioxidants in food should usually by accompanied by the identification and quantification of the phenols. Reversed-phase HPLC combined with UV-VIS or electrochemical detection is the most common method for quantification of individual flavonoids and phenolic acids in foods (Merken and Beecher, 2000 Mattila and Kumpulainen, 2002), whereas HPLC combined with mass spectrometry has been used for identification of phenolic compounds (Justesen et al, 1998). Normal-phase HPLC combined with mass spectrometry has been used to identify monomeric and dimeric proanthocyanidins (Lazarus et al, 1999). Flavonoids are usually quantified as aglycones by HPLC, and samples containing flavonoid glycosides are therefore hydrolysed before analysis (Nuutila et al, 2002). 

MATTILA p and KUMPULAINEN J (2002) Determination of free and total phenolic acids in plant-derived foods by HPLC with diode-array detection, JAgric Food Chem, 50, 3660-67. 

NUUTILA A M, KAMMioviRTA K and OKSMAN-CALDENTEY K-M (2002) Comparison of methods for the hydrolysis of flavonoids and phenolic acids from onion and spinach for HPLC-analysis, Food Chem, 76, 519-25. 

Rice-Evans, C. A. et al.. Structure-antioxidant activity relationships of flavonoids and phenolic acids. Free Radic. Biol. Med., 20, 933, 1996. 

Finally, the fact that anthocyanins can reach the brain represents a beginning of an explanation of the purported neuroprotection effects of anthocyanins. Anthocyanins may be eliminated via urinary and biliary excretion routes. " The extent of elimination of anthocyanins via urine is usually very low (< 0.2% intake) in rats and in humans, indicating either a more pronounced elimination via the bile route or extensive metabolism. As mentioned earlier, in the colon, non-absorbed or biliary excreted anthocyanins can be metabolized by the intestinal microflora into simpler break-down compounds such as phenolic acids that may be (re)absorbed and conjugated with glycine, glucuronic acid, or sulfate and also exhibit some biological... 

Typically lipids, chlorophyll, and phenolic acids can be separated by liquid-liquid partition. Lipids and chlorophyll can be removed from acetone-water extracts by chloroform while phenolic acids have higher affinities for ethyl acetate at a pH close to nentral and water. °°... 

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