0-coumaric acid

CqHaOj. Colourless crystals m.p. lOS C. Obtained by boiling coumarin with sodium ethoxide. Irradiation of o-coumaric acid produces coumarinic acid. The stable form of the acid is the trans form. 

CflHaOa. An unstable acid which spontaneously forms a -lactone, coumarin, when the free acid is generated from its salts. See coumaric acid. 

Fig. 3. Cinnamate biosynthesis from phenylalanine (8) to cinnamic acid (9) or from tyrosine (10) to coumaric acid (11). Coumarylquinic acid (12) is also...

Of these, the CGA isomers are the principal acids and result from the esterification of the 3, 4, and 5 position hydroxyls of quinic acid with the carboxyls of several phenoHc acids, including caffeic acid (C) [331-39-5], ferruHc acid (F) [1135-24-6], andT -coumaric acid (Cm) [501 -98 ]. 

Coumaranone-2-acetic acid, 4,6-dimethyl-synthesis, 3, 850 /3-Coumaranones synthesis, 4, 710 Coumaric acid synthesis, 3, 685 Coumarilic acid... 

Hydroxycinnamic acid (p-coumaric acid) [501-98-4] M 164.2, m 210-213 , 214-215 , 215 pK 4.64, pKj 9.45. Crystd from H2O (charcoal). Needles from cone aqueous solutions as the anhydrous acid, but from hot dilute solutions the monohydrate acid separates on slow cooling. The acid (33g) has been recrystd from 2.5L of H2O (1.5g charcoal) yielding 28.4g of recrystd acid, m 207°. It is insol in CgH6 or pet ether. The UV in 95% EtOH has 223 and 286nm (e 14,450 and 19000 M cm ). [UV Wheeler and Covarrubias J Org Chem 28 2015 7965 Corti Helv Chim Acta 32 681 1949.]... 

Coumarin was first produced synthetically by Perkin. He made it by heating salicylic aldehyde, CgH (OH)i(COH), acetic anhydride, and sodium acetate. The whole solidifies to a crystalline mass, from which, on treatment with water, an oil separates containing coumarin and aceto-coumaric acid. This acid on heating is decomposed into acetic acid and coumarin, so that the product of distillation is principally coumarin. Perkin s synthesis proceeds according to the following equation —... 

The sodium salt of aceto-coumaric acid on hydrolysis decomposes, yielding first an acid which loses water, forming coumarin, together with acetic acid-—... 

On heating this under pressure, with a solution of caustic soda, ortho-hydi oxy-coumaric acid results—... 

On heating with concentrated solution of potash, coumarin is converted into o-coumaric acid, HO. C H. CH CH. COOH, melting at 207° to 208°. 

This acid, CHgO. C,jH. CH CH. COOH, is methyl-p-coumaric acid, and is present in kaempferia oil. It is a crystalline solid melting at 171°. 

Attempts to isolate the postulated substituted p-coumaric acid by hydrolysis have been of no avail, probably partly because of the known proneness of coumaric acid to decarboxylation followed by polymerization (3). In addition, evidence is available that the couma-royl residue is firmly attached to the as yet unexplored moiety of M. 

Although catalytic wet oxidation of acetic acid, phenol, and p-coumaric acid has been reported for Co-Bi composites and CoOx-based mixed metal oxides [3-5], we could find no studies of the wet oxidation of CHCs over supported CoO catalysts. Therefore, this study was conducted to see if such catalysts are available for wet oxidation of trichloroethylene (TCE) as a model CHC in a continuous flow fixal-bed reactor that requires no subsequent separation process. The supported CoOx catalysts were characterized to explain unsteady-state behavior in activity for a certain hour on stream. 

The less specific binding of flavonoids to ferrylmyoglobin is in agreement with establishment of LFERs, linear free energy relationships, i.e. Ink(ferryl) depends linearly on E , for reduction of MbFe(IV)=0 by flavonoids within series of flavonons and ftavonols (Jorgensen and Skibsted, 1998). The relevance of such LFERs, as demonstrated for MbFe(IV)=0 and plant phenols, draws further support from the observation that the same sequence, i.e. chlorogenic caffeic > ferulic > coumaric acid, is seen for reaction of the phenols with... 

Recent scientific investigations of natural polyphenols have demonstrated their powerful antioxidant property (Niki et al, 1995). Several classes of polyphenols have been chemically identified. Some of these are grape polyphenols, tea polyphenols, soy polyphenols, oligomeric proanthocyanidines (OPA) and other natural polyphenols of the flavone class. Rice bran polyphenols are different from the above in that they are p-hydroxy cinnamic acid derivatives such as p-coumaric acid, ferulic acid and p-sinapic acid. Tricin, a flavone derivative, has also been isolated from rice bran. 

Studies by Hudson et al, (2000) have demonstrated the presence of eight polyphenols in rice bran by using high-pressure liquid chromatography. They are protocatechuic acid, p-coumaric acid, ferulic acid, sinapic aci vanillic acid, caffeic acid, which is a methoxycirmamic acid derivative, and tricin. The effect of these polyphenols on cell viability and on the colony-forming ability of human-derived MDA MB 468 and HBL 100 breast cells, colon-derived SW 480 and human colonic epithelial cells was assessed. These authors concluded that rice bran polyphenols have putative cancer chemopreventive properties. 

The effects of catechin, epicatechin, procyanidin B2, caffeic acid, / -coumaric acid, myricetrin, and quercetrin on the color intensity and stability of malvidin 3-glucoside at a molar ratio of 1 1 under conditions similar to red wine were evaluated. " Flavan 3-ols appeared to have the lowest protective effects and flavonols the highest strong color changes were visually perceptible. " In the complexation of malvin chloride and natural polyphenols, flavonol glycosides by far exerted the best protector effect. ... 

George, F. et al., Infinence of trans-cis isomerisation of coumaric acid snbstituents on colonr variance and stabilisation in anthocyanins. Phytochemistry, 57, 791, 2001. 

P. Sathiyamoorthy, Identification of vanillic and p-coumaric acid as endogenous inhibitors of soybean seeds and their inhibitory effect on germination. J. Plant P/m-w/. /id 120 (1990). 

Phenylalanine ammonia-lyase (PAL EC 4.3.1.5) is a pivotal enzyme in controlling flow of carbon from aromatic amino acids to secondary aromatic compounds (Figure 1) (28). PAL primarily deaminates phenylalanine to form t-cinnamic acid, however, in many species, it also less efficiently deaminates tyrosine to form -coumaric acid. Because PAL is restricted to plants and is an important enzyme in plant development, Jangaard (29) suggested that PAL inhibitors might make safe and effective herbicides, however, in his screen of several herbicides, he found no compound to have a specific effect on PAL. This was also the case in studies by Hoagland and Duke (30, 31.) in which 16 herbicides were screened. 

A large number of in vitro inhibitors of PAL are known, however, few of these effectively inhibit PAL activity in vivo without also causing phytotoxic effects unrelated to their effects on PAL. PAL inhibitors fall into four categories 1) PAL product-inhibitors such as t-cinnamic acid and p-coumaric acid (e.g. 35) ... 

Figure 6. Time course of effects of 10 ug chlorsulfuron per seedling on total phenolic content of sunflower hypocotyls expressed as -coumaric acid equivalents. Reproduced with permission from Ref. 75. Copyright 1983, J. Plant Growth Regul.

Effects of jj-Coumaric Acid on the Water Status of Grain Sorghum... 

The reported (14) mechanisms of action of allelochemlcals Include effects on root ultrastructure and subsequent Inhibition of Ion absorption and water uptake, effects on hormone-induced growth, alteration of membrane permeability, changes In lipid and organic acid metabolism, inhibition of protein synthesis and alteration of enzyme activity, and effects on stomatal opening and on photosynthesis. Reduced leaf water potential Is one result of treatment with ferulic and p-coumaric acids (15). Colton and Einhellig (16) found that aqueous extracts of velvetleaf (Abutllon theophrastl Medic.) Increased diffusive resistance In soybean fGlycine max. (L.) Merr.] leaves, probably as a result of stomatal closure. In addition, there was evidence of water stress and reduced quantities of chlorophyll In Inhibited plants. 

Einhellig and Rasmussen (17) reported that In addition to ferulic and p-coumaric acids, vanillic acid reduced chlorophyll content of soybean leaves but did not affect chlorophyll In grain sorghum fSorghum bicolor (L.) Moench.]. It Is not known whether these reported mechanisms are primary or secondary events In the Inhibition of plant growth by allelochemlcals. 

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