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PubMed2004

An Approach towards the quantitative structure-activity relationships of caffeic acid and its derivatives.

Caffeic acid and its derivatives are already known to possess a wide range of biological activities. We have developed quantitative structure-activity relationships (QSARs) for different series of caffeic acid derivatives (including caffeic acid) in order to understand the chemical-biological interactions governing antitumor activity against six different tumor cell lines, nitric oxide production, anti-HIV and enzymatic activities, and binding affinity to the lck domain. QSAR results have shown that the different activities of caffeic acid and its derivatives are largely dependent on their hydrophobicity or molar refractivity, with a bilinear correlation being the most important.

Algorithms↗
PubMed2006

Simultaneous voltammetric measurement of ascorbic acid, epinephrine and uric acid at a glassy carbon electrode modified with caffeic acid.

A stable electroactive thin film of poly(caffeic acid) has been deposited on the surface of a glassy carbon electrode by potentiostatic technique in an aqueous solution containing caffeic acid. Poly(caffeic acid) was used as a modified electrode for the detection of ascorbic acid (AA), epinephrine (EP), uric acid (UA) and their mixture by cyclic voltammetry. This modified electrode exhibits potent and persistent electron-mediating behavior followed by well-separated oxidation peaks towards AA, EP and UA with activation overpotential. For the ternary mixture containing AA, EP and UA, the three compounds can well separate from each other at the scan rate of 20 mVs(-1) with a potential difference of 156, 132 and 288 mV between AA and EP, EP and UA and AA and UA, respectively, which was large enough to determine AA, EP and UA individually and simultaneously. The catalytic peak current obtained, was linearly dependent on the AA, EP and UA concentrations in the range of 2.0 x 10(-5) to 1.0 x 10(-3) mol l(-1), 2.0 x 10(-6) to 8.0 x 10(-5) mol l(-1) and 5.0 x 10(-6) to 3.0 x 10(-4) mol l(-1), and the detection limits for AA, EP and UA were 7.0 x 10(-6), 2.0 x 10(-7) and 6.0 x 10(-7) mol l(-1), respectively. The modified electrode shows good sensitivity, selectivity and stability, and has been applied to the determination of EP in practical injection samples and that of EP, UA and AA simultaneously with satisfactory results.

Ascorbic Acid↗
PubMed2003

[Vasorelaxant activity of caffeic acid derivatives from Cichorium intybus and Equisetum arvense].

The vasorelaxant activities of chicoric acid (Compound 1) from Cichorium intybus and dicaffeoyl-meso-tartaric acid (Compound 2) from Equisetum arvense L. in isolated rat aorta strips were studied. Compound 1 is a diester composed of (S,S)-tartaric acid and caffeic acid, and 2 is composed of its meso type. Both 1 and 2 showed slow relaxation activity against norepinephrine (NE)-induced contraction of rat aorta with/without endothelium. These compounds did not affect contraction induced by a high concentration of potassium (60 mM K+), while they inhibited NE-induced vasocontraction in the presence of nicardipine. These results show that the inhibition by 1 and 2 of NE-induced vasocontraction is due to a decrease in calcium influx from the extracellular space caused by NE. In addition, dicaffeoyl tartaric acids showed vasorelaxant activity, regardless of their stereochemistry.

Animals↗
PubMed2003

[Study on the spectral properties of caffeic acid and its derivatives].

Caffeic acid, chlorogenic acid and forsythiaside are active components of Chinese herbs and have diverse biological activities. As the similar compounds, they all include 3, 4-dihydroxy-phenyl in their structures. In this paper, the fluorescence and UV spectra of the caffeic acid, chlorogenic acid and forsythiaside were studied in different pH. The spectra properties of fluorescence and UV were further discussed in view of the phenol hydroxyl states, free, dissociative and protonated. It is found that the luminescence intensity, the peak shape and peak wavelength change with pH. Experimental results also indicate that caffeic acid, chlorogenic acid and forsythiaside can emit fluorescence in wide range of pH (2-12), and fluorescent intensity is enhanced as the dissociation of 4-phenol hydroxyl. On the other hand, fluorescent intensity may be quenched as the dissociation of 3-phenol hydroxyl. Furthermore, in strong acidic or in strong basic media, the fluorescence is quenched partly, and the shape of UV spectra changed greatly in strong basic media, meaning that their molecular structures are changed considerable.

Anti-Infective Agents↗
PubMed1990

High-performance liquid chromatography and diffuse reflectance spectroscopy of flavonoids in Crataegus oxyacantha L. III--Analysis of 2-phenyl-chroman derivatives and caffeic acid.

High-performance liquid chromatographic (HPLC) and diffuse infrared reflectance spectroscopic techniques for qualitative and quantitative analysis of naturally occurring phenolic compounds in Crataegus oxyacantha L. have been applied. (+)-Catechin, (-)-epicatechin and a phenolic acid, the caffeic acid, were investigated in various extractives of Crataegus oxyacantha L. The reversed-phase chromatographic separation was achieved by a combination of isocratic and gradient elution.

Caffeic Acids↗
PubMed2001

Structure of green pigment formed by the reaction of caffeic acid esters (or chlorogenic acid) with a primary amino compound.

A marked greening observed in some foods such as sweet potato, burdock, and others during food processing was shown to be due to green pigment formation by the condensation reaction of two molecules of chlorogenic acid or caffeic acid ester with one molecule of a primary amino compound under aeration in alkaline solution. Reduction of the green pigment by ascorbic acid or NaBH4 gave a yellow product, which readily turn green and then blue in air. The reduced and acetylated product of the green pigment was identified to be a novel trihydroxy benzacridine derivative, and the yellowish ethanol solution of this product immediately turned green upon addition of butyl amine or diluted alkali. Therefore, the green pigment was assumed to be an oxidized quinone type product of trihydroxy benzacridine. This identification of the structure was supported by the correspondence of the measured absorption spectra with those calculated by the molecular orbital method. A possible charge transfer complex between products of different oxidation steps in green solution was proposed.

Acetylation↗
PubMed2005

Chemistry and biological activities of caffeic acid derivatives from Salvia miltiorrhiza.

Caffeic acid (3,4-dihydroxycinnamic acid), one of the most common phenolic acids, frequently occurs in fruits, grains and dietary supplements for human consumption as simple esters with quinic acid or saccharides, and are also found in traditional Chinese herbs. Caffeic acid derivatives occur as major water-soluble components of Salvia miltiorrhiza, including caffeic acid monomers and a wide variety of oligomers. This review provides up-to-date coverage of this class of phenolic acids in regard to structural classification, natural resources, chemical and biosyntheses, analytical methods and biological activities including antioxidant, anti-ischemia reperfusion, anti-thrombosis, anti-hypertension, anti-fibrosis, antivirus and antitumor properties. Special attention is paid to both structural classification and biological activities. The structural diversity and the pronounced biological activities encountered in the caffeic acid derivatives of S. miltiorrhiza indicate that this class of compounds is worthy of further studies that may lead to new drug discovery.

Anti-Infective Agents↗
PubMed2005

Downregulation of Rac1 activation by caffeic acid in aortic smooth muscle cells.

Caffeic acid, a dietary phenol from coffee, fruits and vegetables, is an efficient antioxidant. However, little is known about its anti-oxidative mechanism in the modulation of fundamental cellular processes. In this study, we investigated whether caffeic acid regulates Rac1 GTPase activity, a partner of NADPH oxidase. Our results showed that caffeic acid decrease Rac1 protein level under basal conditions and incubation with angiotensin II (ANG II) in vascular smooth muscle cells. In a Rac-bound-to-PAK pull down assay, caffeic acid clearly inhibited Rac1 activity. We also observed that caffeic acid suppressed the generation of superoxide anion stimulated by ANG II that activates NADPH oxidase. On the other hand, co-incubation with caffei caid and cycloheximide significantly accelerated the Rac1 degradation. In addition, pretreatment with caffeic acid for 24 hours was able to prevent phosphorylation of MLC and HSP27, when cells were challenged with ANG II through the redox sensitive pathway. These results support the hypothesis that caffeic acid reduces Rac1 GTPase protein and activity level, followed by a down-regulation of NADPH oxidase activity.

Analysis of Variance↗
PubMedDate not supplied

Structure-activity relationship of caffeic acid analogues on xanthine oxidase inhibition.

Caffeic acid has been reported to have activity on xanthine oxidase inhibition which is related to several diseases, e.g. gout, hepatitis and tumors. Based on this study, the alpha, beta-unsaturated COOH moiety in the molecule of caffeic acid plays a very important role on the xanthine oxidase inhibition because hydrocaffeic acid was inactive and the activities of coniferyl aldehyde and coniferyl alcohol were reduced as compared with ferulic acid. Moreover, chlorogenic acid showed a weaker activity than caffeic acid. On the other hand, the phenolic OH group present in the molecule of caffeic acid makes an important contribution to the activity, e.g. transcinnamic acid in which the absence of the phenolic OH group in the structure reduced its activity as compared with caffeic acid. Ferulic acid, isoferulic acid and 3,4-dimethoxy cinnamic acid also had reduced activity due to the methoxy groups replacing the phenolic OH group in the structures. However, m-coumaric acid displayed the strongest activity (IC50 = 63.31 microM) and induced uncompetitive inhibition with respect to the substrate xanthine (Ki = 21.568 microM). Caffeic acid (IC50 = 74.6 microM) showed the second strongest activity, followed by p-coumaric acid (IC50 = 111.09 microM).

Caffeic Acids↗
PubMed2006

Microbial metabolism of caffeic acid and its esters chlorogenic and caftaric acids by human faecal microbiota in vitro.

Caffeic acid and its esters, chlorogenic and caftaric acids, are major dietary polyphenols present in various foods and beverages. Although caffeic acid is easily absorbed in the small intestine, its esterification with quinic acid, as in chlorogenic acid, decreases its gut absorption and increases the quantities reaching the colon and its microbiota. The microbial conversion of caftaric acid, the tartaric acid ester of caffeic acid, has not been studied earlier. In this work we compared the direct action of a human faecal microbiota on the metabolism of caffeic, chlorogenic and caftaric acids in an in vitro fermentation model. All substrates disappeared quickly and none of the free acids (caffeic, quinic or tartaric acids) were detected after 2 hours of incubation. Two major microbial metabolites were identified by HPLC-ESI-MS-MS as 3-hydroxyphenylpropionic (3-HPP) and benzoic acids (BA). Maximal levels of 3-HPP were reached after 2 h of fermentation and accounted for 9-24% of the dose of caffeic acid and its esters. BA was formed steadily throughout the incubation, accounting for 4-5% of the initial dose of the substrates after 24 h of incubation. The similarities in the metabolic patterns observed for caffeic, chlorogenic and caftaric acids suggest that esterification does not influence the metabolism of caffeic acid by the gut microbiota.

Bacteria↗
PubMed2005

Inhibition of neutrophil elastase and thrombin activity by caffeic acid esters.

Natural and synthetic caffeic acid esters were assayed for their enzymatic activity versus neutrophil elastase (EC 3.4.21.37) and thrombin (EC 3.4.21.5). Lipophilic caffeic acid esters inhibited neutrophil elastase activity and the inhibition rate was enhanced with increasing length of the aliphatic chain of the alcohol component. The geometry of the chain seems to be more important than the number of carbon atoms. The most inhibitory compound was n-octylcaffeic acid ester with an IC50 value of 1.0 microM. Thrombin activity was only weakly inhibited by the caffeic acid esters thus demonstrating a specificity for neutrophil elastase. Because of its critical role in inflammatory processes, inhibition of neutrophil elastase by caffeic acid esters might be of importance in the treatment of inflammation.

Caffeic Acids↗
PubMed1993

Inhibition of tumor promoter-mediated processes in mouse skin and bovine lens by caffeic acid phenethyl ester.

Caffeic acid phenethyl ester (CAPE) was isolated from propolis (a product of honeybee hives) that has been used in folk medicine as a potent antiinflammatory agent. CAPE is cytotoxic to tumor and virally transformed but not to normal cells. Our main goal was to establish whether CAPE inhibits the tumor promoter (12-O-tetradecanoylphorbol-13-acetate)-induced processes associated with carcinogenesis. Topical treatment of SENCAR mice with very low doses (0.1-6.5 nmol/topical treatment) of CAPE strongly inhibits the following 12-O-tetradecanoylphorbol-13-acetate-mediated oxidative processes that are considered essential for tumor promotion: (a) polymorphonuclear leukocyte infiltration into mouse skin and ears, as quantified by myeloperoxidase activity; (b) hydrogen peroxide (H2O2) production; and (c) formation of oxidized bases in epidermal DNA, as measured by 5-hydroxymethyluracil and 8-hydroxylguanine. A 0.5-nmol dose of CAPE suppresses the oxidative burst of human polymorphonuclear leukocytes by 50%. At higher doses (1-10 mumol), CAPE inhibits edema and ornithine decarboxylase induction in CD-1 and SENCAR mice. Interestingly, we discovered that 12-O-tetradecanoylphorbol-13-acetate-induced H2O2 production in bovine lenses also is inhibited by CAPE. Cumulatively, these findings point to CAPE as being a potent chemopreventive agent, which may be useful in combating diseases with strong inflammatory and/or oxidative stress components, i.e., various types of cancer and possibly cataract development.

Animals↗
PubMed2001

Suppression of cell transformation and induction of apoptosis by caffeic acid phenethyl ester.

Caffeic acid phenethyl ester (CAPE), which is derived from the propolis of honeybee hives, has been shown to block tumor promotion and to have toxic effects on several cancer cells. The mechanism of the anti-tumor promotion activity of CAPE is unclear, however. In this study, we found that CAPE suppressed 12-O-tetradecanoylphorbol-13-acetate-induced cell transformation and induced apoptosis in mouse epidermal JB6 Cl 41 cells. No difference in induction of apoptosis was observed between normal lymphoblasts and sphingomyelinase-deficient cell lines. Although CAPE treatment of two p53 mutant tumor cell lines, NCI-H358 and SK-OV-3, and p53-deficient (p53(-/-)) cells caused the cleavage of caspase-3 as well as DNA fragmentation, caspase-3 cleavage was seen early (at 6 h) only in cells expressing wild-type p53 (p53(+/+)) and Cl 41 cells. These results suggested that p53 may be involved in the early stage of CAPE-induced apoptosis. The p53-dependent transcription activation occurred 2 h after treatment with CAPE and reached a maximum at 6 h in Cl 41 p53 DNA-binding sequence stable transfectant cells. In addition, phosphorylation of p53 at serine 15 and serine 392 was induced in Cl 41 cells within 6 h after treatment with CAPE. Therefore, CAPE may induce apoptosis through p53-dependent and p53-independent pathways and its anti-tumor promotion activity may have occurred through the induction of apoptosis.

Animals↗
PubMed2004

Differentiation of HL-60 myeloid leukemia cells induced by all-trans retinoic acid is enhanced in combination with caffeic acid.

We investigated a possible enhancement of all-trans retinoic acid (ATRA)-induced differentiation of HL-60 human myeloid leukemia cells by caffeic acid (CA), a widely distributed plant phenolic compound. Our results showed that CA, in the concentration of 13 or 52 micro M, had no or minimal influence on cell differentiation, whereas the differentiating activity of ATRA was potentiated by CA treatment. We proved, using flow cytometric detection of the CD66b surface molecule, a synergistic effect of CA: at day 10, 18.3% of CD66b-positive cells were detected after treatment with ATRA only, and 33% when CA and ATRA were combined together. NBT-assay confirmed that this additive effect of CA on ATRA-induced differentiation. Proliferating activity as assessed by MTT-assay was generally not affected by CA at given concentrations. However, cell proliferation was significantly reduced by 52 micro M CA at 96-h intervals. This effect was markedly enhanced when CA, at both concentrations, and ATRA were combined. The possibility to enhance the differentiation potential of ATRA by CA may improve outcomes in the therapy of acute promyelocytic leukemia.

Antigens, CD↗
PubMed2002

Stabilization of caffeic acid derivatives in Echinacea purpurea L. glycerin extract.

Recent work has shown that enzymatic degradation and oxidation of cichoric acid and other caffeic derivatives occurs in Echinacea preparations. However, very little is known as to the means of stabilizing these phytopreparations. To stabilize the glycerin extract of Echinacea purpurea, we have evaluated the effects of 3 natural antioxidants (citric acid, malic acid, and hibiscus extract) on the stability of the major caffeic acid derivatives (caftaric acid, caffeic acid, cichoric acid, and 2-O-feruloyl-tartaric acid). Chlorogenic acid, which normally occurs in an ethanol extract of E. purpurea, was not present in the glycerin extract. The caffeic acid derivatives, with the exception of 2-O-feruloyl-tartaric acid, were subject to degradation in the control sample. 2-O-Feruloyl-tartaric acid was stable during the whole testing period. All antioxidant treatments greatly improved the stability of caffeic acid derivatives. Stability was dependent upon the concentration of antioxidant added.

Antioxidants↗
PubMed2002

Antioxidant activity of propolis: role of caffeic acid phenethyl ester and galangin.

Propolis, a natural product produced by the honeybee, has been used for thousands of years in folk medicine for several purposes. The extract contains amino acids, phenolic acids, phenolic acid esters, flavonoids, cinnamic acid, terpenes and caffeic acid. It possesses several biological activities such as antiinflammatory, immunostimulatory, antiviral and antibacterial. The exact mode of physiological or biochemical mechanisms responsible for the medical effects, however, is yet to be determined. In this work, we have investigated the antioxidant activity of a propolis extract deprived of caffeic acid phenethyl ester (CAPE). In addition, the activity of CAPE and galangin was also examined. Propolis extract (with and without CAPE) and its active components showed a dose-dependent free radical scavenging effect, a significant inhibition of xanthine oxidase activity, and an antilipoperoxidative capacity. Propolis extract with CAPE was more active than propolis extract without CAPE. CAPE, used alone, exhibited a strong antioxidant activity, higher than galangin. The experimental evidence, therefore, suggests that CAPE plays an important role in the antioxidant activity of propolis.

Antioxidants↗
PubMed1993

Metabolism of caffeic acid in the isolated perfused rat liver.

Caffeic acid as well as its oxidation products exert a spectrum of biological effects in in vitro testing. To get an idea of the amount as well as the mode of biotransformation, caffeic acid metabolism was investigated by means of the isolated perfused rat liver. The first-pass effect was not pronounced: 93.3% of caffeic acid dose appeared unchanged after one liver passage. Products of caffeic acid oxidation (cyclolignan derivatives) as well as ferulic and isoferulic acid as methylation products were found in the perfusion medium. In addition, a cyclization product, esculetin, was observed. In the bile, mainly glucuronides as well as sulfates of caffeic acid could be determined. Thus, oxidation products and other metabolites formed by liver metabolism can be responsible for the biological effects in vivo.

Animals↗