Phenolic acid, isolation

The phenolic acids isolated from aniseed include caffeic acid, hydroxybenzoic acid, hydroxycinnamic acid and p-coumaric... 

Azuma, J., Nomura, T., and Koshijima, T. (1985) Lignin-carhohydrate complexes containing phenolic acids isolated from the cuhns of hamhoo. Agric. Biol. Chem. 49, 2661-2669. 

It is a phenolic acid, isolated from a Penicillium sp. and shows inhibitory activity against HSV-1 and -2, VV, Semliki forest, influenza A viruses and coxsackievirus. Its effect is probably due to cytotoxicity [19]. 

Fig. 3.8 Phenolic acids extracted from wheat stubble, wheat straw from half buried litter bags, and wheat stubble/soybean (no-till) soil. Phenolic acids isolated and quantified were caffeic acid (CAF), ferulic acid (FER), p-coumaric acid (PCO), p-hydroxybenzoic acid (POH), sinapic acid (SIN), syringic acid (SYR), and vanillic acid (VAN). Becausep-coumaric acid was so high in comparison to other phenolic acids in wheat residues, data are presented twice, once with p-coumaric acid (a) and once without p-coumaric acid (b). Because phenolic acids were so low in the soil they are also presented in (c). The absence of standard error bars for wheat straw and soil indicates that the error bars are too small to be visible. Figures based on data from Blum et al. (1991, 1992). Plenum Publishing Corporation, data used with permission of Springer Science and Business Media...

Fernandez, M. A., M. T. Saenz, and M. D. Garcia. 1998. Anti-inflammatory activity in rats and mice of phenolic acids isolated from Scrophularia frutescens. J. Pharm. Pharmacol. 50 1183-1186. 

Males et al. [103] used aqueous mobile phase with formic acid for the separation of flavonoids and phenolic acids in the extract of Sambuci flos. In a cited paper, authors listed ten mobile phases with addition of acids used by other investigators for chromatography of polyphenolic material. For micropreparative separation and isolation of antraquinone derivatives (aloine and aloeemodine) from the hardened sap of aloe (Liliaceae family), Wawrzynowicz et al. used 0.5-mm silica precoated plates and isopropanol-methanol-acetic acid as the mobile phase [104]. The addition of small amounts of acid to the mobile phase suppressed the dissociation of acidic groups (phenolic, carboxylic) and thus prevented band diffusions. 

Aljadi, A. M. and Yusoff, K. M. (2003). Isolation and identification of phenolic acids in Malaysian honey with antibacterial properties. Turk. J. Med. Sci. 33, 229-236. 

Effects of Allelochemlcals on ATPases. Several flavonoid compounds inhibit ATPase activity that is associated with mineral absorption. Phloretin and quercetin (100 pM) inhibited the plasma membrane ATPase Isolated from oat roots (33). The naphthoquinone juglone was inhibitory also. However, neither ferulic acid nor salicylic acid inhibited the ATPase. Additional research has shown that even at 10 mM salicylic acid inhibits ATPase activity only 10-15% (49). This lack of activity by salicylic acid was substantiated with the plasma membrane ATPase Isolated from Neurospora crassa (50) however, the flavonols fisetln, morin, myricetin, quercetin, and rutin were inhibitory to the Neurospora ATPase. Flavonoids inhibited the transport ATPases of several animal systems also (51-53). Thus, it appears that flavonoids but not phenolic acids might affect mineral transport by inhibiting ATPase enzymes. 

Although several allelochemicals (primarily phenolic acids and flavonoids) have been shown to inhibit mineral absorption, only the phenolic acids have been studied at the physiological and biochemical levels to attempt to determine if mineral transport across cellular membranes can be affected directly rather than indirectly. Similar and even more definitive experiments need to be conducted with other allelochemicals that are suspected of inhibiting mineral absorption. Membrane vesicles isolated from plant cells are now being used to elucidate the mechanism of mineral transport across the plasma membrane and tonoplast (67, 68). Such vesicle systems actively transport mineral ions and thus can serve as simplified systems to directly test the ability of allelochemicals to inhibit mineral absorption by plant cells. 

It was unfortunate that we did not detect any product derived from a diketone in the reaction of w-dimethoxybenzene with tetrafluoroben-zyne. We therefore carried out a reaction of tetrafluorobenzyne with 1,3,5-trimethoxybenzene. The di-enol ether (80) could not be isolated, and after the removal of unreacted 1,3,5-trimethoxybenzene we isolated the phenolic acid (81) in good yield. This compound is undoubtedly formed by the hydrolysis of (80) followed by a retro-Claisen condensation, and aromatisation as shown below. 

The unharvested parts of rice plants are generally mixed with the soil because this has been thought to be beneficial. It has been observed however, that productivity of the second crop of rice in a paddy is less than that of the first crop. Chou and Lin (45) found that aqueous extracts of decomposing rice residues in soil retarded radicle growth of rice seedlings and growth of rice plants. Maximum toxicity occurred in the first month of decomposition and declined thereafter. Some toxicity persisted for four months in the paddies. Five inhibitory phenolic acids were identified from decaying rice residues and several unidentified allelochemicals were isolated. 

UDPG-GTases that use phenolic acids as acceptor molecules have been Isolated from several plant tissues. These include leaves of sweet clover (28), geranium (29), Oestrum euenthes (30), oak (31,... 

Effects of Phenolic Acids, Coumarins, and Flavonoids on Isolated Chloroplasts and Mitochondria... 

The objectives of the studies reported herein were to (a) compare the effects of a series of phenolic acids, coumarins, and flavonoids on whole chain electron transport and phosphorylation in Isolated plant chloroplasts and mitochondria and (b) identify specific sites of inhibition with polarographic and enzymatic techniques. Exploratory studies were conducted with the 20 compounds listed in Table I. The three glycosides are shown indented below the corresponding aglycones. Detailed studies were conducted with the six compounds, one representative member from each chemical family, designated with an asterisk. 

FIGURE 19.9 HPLC chromatogram of standards of phenolic acids, flavonols, flavones, and glycosides isolated in onions and spinach. (From Nnntila, A.M. et al., Food Chem., 76, 519, 2002. Copyright 2002. With permission from Elsevier.)... 

Materska, M. et al.. Isolation and structure elucidation of flavonoid and phenolic acid glycosides from pericarp of hot pepper fruit Capsicum annum L., Phytochemistry, 63, 893, 2003. 

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... 

Phenolic acids are ionized at pH 7.0 and are un-ionized at pH 2.0. This property allows for solid-phase extraction of neutral polyphenolics at pH 7.0 and acidic polyphenolics at pH 2.0 to prevent interference. In this protocol, polyphenolics isolated as neutral and acidic fractions using pH adjustments are analyzed by reversed-phase HPLC in a thermostatically controlled environment. 

Retention times of the peaks are subject to the particular type of column. The acidic fraction from solid-phase extraction consists of phenolic acids such as cis-coutaric, trans-coutaric, and trans-caftaric acids. Isocratic elution is suitable because of the limited number of compounds found in the acidic fraction. Analysis of the acidic fraction is completed within 30 min. See Figure 11.3.1 for an HPLC chromatogram of the acidic polyphenolics isolated from Niagara grapes. 

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