P-Coumarates

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.]... 

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. 

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. 

Advances in analytical procedures resulted in several reports on anthocyanins acy-lated with hydroxycinnamic acids (p-coumaric, caffeic, ferulic, sinapic, and 3,5-dihydroxycinnamic acids), hydroxybenzoic acids (p-hydroxybenzoic and gallic acids), and aliphatic acids (malonic, acetic, malic, oxalic, succinic and tartaric acids). However, not all of them were found in anthocyanins isolated from foods. Among the 44 fruits listed in Table 4.3.1, 15 presented acylated anthocyanins as did 12 of 13 vegetables shown in Table 4.3.3 and 2 of the 9 grains cited in Table 4.3.4. On the other hand, acylated anthocyanins were found in all grapes from Vitis species, although at different abundance levels, as can be seen in Table 4.3.2. A higher... 

The pure enzyme was tested for activity against several methylated phenolic and cinnamic acids (Table 2). The enzyme was active on methyl esters of cinnamic acids caffeio p-coumaric> ferulic, and is therefore termed a cinnamoyl esterase (CinnAE). 

Degrassi G, PP de Laureto, CV Bruschi (1995) Purification and chracterization of ferulate and p-coumarate decarboxylase from Bacillus pumilis. Appl Environ Microbiol 61 326-332. 

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. 

Aromatic acids p-Hydroxybenzoic, caffeic, p-coumaric, ferulic, gallic, gen-tisic, protocatechuic, salicylic, sinapic, syringic... 

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). 

Hatfield, R. D. Ralph, J. Grabber, J. H. A potential role of sinapyl p-coumarate as a radical transfer mechanism in grass lignin formation. Planta 2008, 228, 919-928. 

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) ... 

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. 

Cynodon dactylon, dried leaves Phenolics - p-coumaric acid 74... 

Sorghum halepense, leaves, rhizomes Chlorogenic, p-coumaric acids, p-hydroxybenzaldehyde 5, 86... 

Oxidation intermediates and reaction pathways of wet hydrogen peroxide oxidation of p-coumaric acid over (Al-Fe)PILC catalyst... 

Keywords Catalytic wet hydrogen peroxide oxidation, Iron, p-Coumaric acid, Pillared clay, Olive oil mill effluents. 

In the present study, we have focused our attention on the catalytic wet peroxide oxidation of p-coumaric acid over (Al-Fe)PILC. This phenolic molecule was chosen as a representative of the biologically recalcitrant polyphenolic compounds present in olive oil processing and wine distillery wastewaters. 

The experiments were performed with different concentration of p-coumaric acid. While in most cases, 500 ppm solutions were employed, saturated p-coumaric acid solutions (700ppm) were more suitable for detecting minor intermediates, p-coumaric acid and intermediates compounds evolution was monitored by HPLC equipped with a Yarian OmniSpher 5 Cig column. Identification and quantitations were achieved by comparison with standards. TOC analyses were carried out using a Shimadzu mod 5000 A apparatus. 

Fig 1 shows the rate of p-coumaric acid solution (500ppm) and TOC removals during the phenolic compound oxidation over (Al-Fe)PILC catalyst (0.5g/l), as well as the uncatalysed reaction in slurry at 70°C. 

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