Caffeic Acid Phenethyl Ester Analogues Research Articles

Caffeic acid phenethyl ester analogues as selective inhibitors of 12-lipoxygenase product biosynthesis in human platelets.

The inflammatory response is an essential process for the host defence against pathogens. Lipid mediators are important in coordinating the pro-inflammatory and pro-resolution phases of the inflammatory process. However, unregulated production of these mediators has been associated with chronic inflammatory diseases such as arthritis, asthma, cardiovascular diseases, and several types of cancer. Therefore, it is not surprising that enzymes implicated in the production of these lipid mediators have been targeted for potential therapeutic approaches. Amongst these inflammatory molecules, the 12-hydroxyeicosatetraenoic acid (12(S)-HETE) is abundantly produced in several diseases and is primarily biosynthesized via the platelet's 12-lipoxygenase (12-LO) pathway. To this day, very few compounds selectively inhibit the 12-LO pathway, and most importantly, none are currently used in the clinical settings. In this study, we investigated a series of polyphenol analogues of natural polyphenols that inhibit the 12-LO pathway in human platelets without affecting other normal functions of the cell. Using an ex vivo approach, we found one compound that selectively inhibited the 12-LO pathway, with IC50 values as low as 0.11µM, with minimal inhibition of other lipoxygenase or cyclooxygenase pathways. More importantly, our data show that none of the compounds tested induced significant off-target effects on either the platelet's activation or its viability. In the continuous search for specific and better inhibitors targeting the regulation of inflammation, we characterized two novel inhibitors of the 12-LO pathway that could be promising for subsequent in vivo studies.

Phenolic acid phenethylesters and their corresponding ketones: Inhibition of 5-lipoxygenase and stability in human blood and HepaRG cells.

5‐lipoxygenase (5‐LO) catalyzes the biosynthesis of leukotrienes, potent lipid mediators involved in inflammatory diseases, and both 5‐LO and the leukotrienes are validated therapeutic targets. Caffeic acid phenethyl ester (CAPE) is an effective inhibitor of 5‐LO and leukotriene biosynthesis but is susceptible to hydrolysis by esterases. In this study a number of CAPE analogues were synthesized with modifications to the caffeoyl moiety and the replacement of the ester linkage with a ketone. Several new molecules showed better inhibition of leukotriene biosynthesis than CAPE in isolated human neutrophils and in whole blood with IC50 values in the nanomolar (290‐520 nmol/L) and low micromolar (1.0‐2.3 µmol/L) ranges, respectively. Sinapic acid and 2,5‐dihydroxy derivatives were more stable than CAPE in whole blood, and ketone analogues were degraded more slowly in HepaRG hepatocyte cultures than esters. All compounds underwent modification consistent with glucuronidation in HepaRG cultures as determined using LC‐MS/MS analysis, though the modified sinapoyl ketone (10) retained 50% of its inhibitory activity after up to one hour of incubation. This study has identified at least one CAPE analogue, compound 10, that shows favorable properties that warrant further in vivo investigation as an antiinflammatory compound.

Caffeic acid phenethyl ester activation of Nrf2 pathway is enhanced under oxidative state: Structural analysis and potential as a pathologically targeted therapeutic agent in treatment of colonic inflammation

Caffeic acid phenethyl ester (CAPE) is a polyphenolic natural product that possesses numerous biological activities including anti-inflammatory effects. CAPE-mediated nuclear factor-erythroid 2 p45 (NF-E2)-related factor 2 (Nrf2) activation is likely responsible for some of its biological effects. CAPE was chemically modified to yield CAPE analogues that were subjected to experiments examining cellular Nrf2 activity. CAPE and the CAPE analogue with a catechol moiety, but not the other analogues, activated the Nrf2 pathway. In addition, only biotin-labeled CAPE analogues with the catechol moiety precipitated Kelch-like ECH associated protein 1 (Keap1) when incubated with cell lysates and streptavidin agarose beads. Sodium hypochlorite (NaOCl) oxidation of the catechol moiety in CAPE produced an oxidized, electrophilic form of CAPE (Oxi-CAPE) and greatly enhanced the ability of CAPE to activate Nrf2 and to bind to Keap1. Rectal administration of CAPE ameliorated 2,4,6-trinitrobenzene sulfonic acid-induced rat colitis and activated the Nrf2 pathway in the inflamed colon, and incubation of CAPE in the lumen of the inflamed distal colon generated Oxi-CAPE. However, these biological effects and chemical change of CAPE were not observed in the normal colon. Our data suggest that CAPE requires the catechol moiety for the oxidation-enhanced activation of the Nrf2 pathway and has potential as a pathologically targeted Nrf2-activating agent that is exclusively activated in pathological states with oxidative stress such as colonic inflammation.

The effect of caffeic acid phenethyl ester analogues in a modified resistant hepatocyte model

We present a study of the chemoprotective effects of two caffeic acid phenethyl ester (CAPE)-related structures: LQM717 and LQM706. The modified resistant hepatocyte model in rats was used to study the chemoprevention of these CAPE analogues, which are inexpensive and easily obtained. In the liver cancer model used, we detected extensive necrosis and lipid peroxidation after 24 h, many altered hepatic foci, putatively preneoplastic lesions with γ-glutamyl transpeptidase staining after 30 days, and liver tumors at 12 months. We tested the effect of the CAPE analogues on necrosis, lipid peroxidation, proliferation, p65 activation, altered hepatic foci, and tumors. Both compounds exerted protective effects on lipid peroxidation, necrosis, cell proliferation, p65 activation, and preneoplastic lesions. Rats under a carcinogenic protocol showed a 52, 71.74, and 51.6% decrease in the number of preneoplastic nodules when pretreated with CAPE, LQM706, and LQM717, respectively. At 12 months after carcinogenic treatment, eight of eight rats developed liver cancer, whereas in the group of rats that received pretreatment with CAPE, LQM706, or LQM717, 62.5, 83.3, or 42.85%, respectively, had tumors. In conclusion, LQM717 has the potential to enhance chemoprotection activity much better than CAPE by markedly reducing the formation of liver cancers in this model, and this is a compound that is easy to obtain.

Synthesis and Antiradical/Antioxidant Activities of Caffeic Acid Phenethyl Ester and Its Related Propionic, Acetic, and Benzoic Acid Analoguesc

Caffeic acid phenethyl ester (CAPE) is a bioactive component isolated from propolis. A series of CAPE analogues was synthesized and their antiradical/antioxidant effects analyzed. The effect of the presence of the double bond and of the conjugated system on the antioxidant effect is evaluated with the analogues obtained from 3-(3,4-dihydroxyphenyl) propanoic acid. Those obtained from 2-(3,4-dihydroxyphenyl) acetic acid and 3,4-dihydroxybenzoic acid allow the evaluation of the effect of the presence of two carbons between the carbonyl and aromatic system.

Enzymatic synthesis of caffeic acid phenethyl ester analogues in ionic liquid

An efficient procedure for transesterification of methyl caffeate was developed to produce caffeic acid phenethyl ester analogues with Candida antarctica lipase B using an ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, as a solvent. The system provided 48.8 mM 2-cyclohexylethyl caffeate and 46.9 mM 3-cyclohexylpropyl caffeate with conversion yields of 97.6% and 93.8%, respectively. Reusability of the system was investigated, and the yield of 4-phenylbutyl caffeate was increased from 30.4 to 45.7 mM when the transesterification was carried out under reduced pressure to remove a by-product, methanol. Additionally, we showed that both 2-cyclohexylethyl caffeate and 3-cyclohexylpropyl caffeate exhibit strong antiproliferative activities, which are comparable to that of 5-fluorouracil by MTT assay.

Structure–activity relationships in the cytoprotective effect of caffeic acid phenethyl ester (CAPE) and fluorinated derivatives: Effects on heme oxygenase-1 induction and antioxidant activities

To determine the relationship between catechol ring modifications and the activity of caffeic acid phenethyl ester (CAPE) as a cytoprotective agent, six catechol ring-fluorinated CAPE derivatives were evaluated for their cytoprotective abilities, as well as for their antioxidant and heme oxygenase-1 (HO-1) inducing capacity in a human umbilical vein endothelial cell (HUVEC) model of oxidant stress. To ascertain the involvement of HO-1 induction in the cytoprotective effects of CAPE analogues, their ability to induce HO-1 at 20 µM was determined by reverse transcriptase polymerase chain reaction, western blotting and the use of HO-1 inhibitor tin protoporphyrin IX. There was significant induction of HO-1 by CAPE derivatives. Inhibition of HO-1 enzymatic activity resulted in reduced cytoprotection. Modification of the catechol ring of CAPE by introduction of fluorine at various positions resulted in dramatic changes in cytoprotective activity. The maintenance of at least one hydroxyl group on the CAPE catechol ring and the phenethyl ester portion was required for HO-1 induction. CAPE and its derivatives were screened for their ability to scavenge intracellular reactive oxygen species generated in HUVECs by measuring 5-(and-6)-chlormethyl-2′, 7′-dichlorodihydrofluorescein diacetate oxidation. The maintenance of 3, 4-dihydroxyl groups on the catechol ring was required for antioxidant activity, but antioxidant activity did not guarantee cytoprotection. Methylation or replacement of one hydroxyl group on the catechol ring of CAPE, however, provided both pro-oxidant and cytoprotective activities. These results indicate that the induction of HO-1 plays a more important role in the cytoprotective activity of CAPE derivatives than their direct antioxidant activity.

Synthesis and ABTS Radical, MMP‐1 Inhibitory Activity of CAPE Analogues

AbstractIn the photoaging process of skin, the ultraviolet (UV)‐induced reactive oxygen species (ROS) is the key regulator of matrix metalloproteinase (MMPs) expression. In this study, a series of Caffeic acid phenethyl ester (CAPE) analogues were synthesized by conjugating the group VI elements (selenium, sulfur, oxygen)‐containing aliphatic alcohols to polyphenolic acids. Their biological activities were evaluated by in vitro testing of their radical scavenging activity the of ABTS [2,2′‐azinobis‐(3‐ethyl‐benzothiazoline‐6‐sulfonic acid)] radical and inhibitory effect against the matrix metalloproteinase‐1 (MMP‐1) activity of collagen degradation and cytotoxicity of a human dermal fibroblast skin cell. Our results suggest these compounds displayed moderate anti‐free radical, potent MMP‐1 inhibitory, and low cytotoxic activities.

Caffeic acid phenethyl ester (CAPE) analogues: potent nitric oxide inhibitors from the Netherlands propolis.

The MeOH and water extracts of the Netherlands propolis were tested for their inhibitory activity toward nitric oxide (NO) production in lipopolysaccharide (LPS)-activated murine macrophage-like J774.1 cells. Both of the extract possessed significant NO inhibitory activity with IC(50) values of 23.8 and 51.5 microg/ml, respectively. Then 13 phenolic compounds obtained from the MeOH extract showing stronger NO inhibition were examined on their NO inhibitory activities. Caffeic acid phenethyl ester (CAPE) analogues, i.e., benzyl caffeate, CAPE and cinnamyl caffeate, possessed most potent NO inhibitory activities with IC(50) values of 13.8, 7.64 and 9.53 microM, respectively, which were two- to four-fold stronger than the positive control N(G)-monomethyl-L-arginine (L-NMMA; IC(50), 32.9 microM). Further study on the synthetic analogues of CAPE revealed that both of 3-phenylpropyl caffeate (18; IC(50), 7.34 microM) and 4-phenylbutyl caffeate (19; IC(50), 6.77 microM) possessed stronger NO inhibitory activity than CAPE (10) and that elongation of alkyl side chain of alcoholic parts of caffeic acid esters enhance the NO inhibitory activity. In addition, it was found that CAPE analogues having longer carbon chain (>C(5)) in alcoholic part showed toxic effects toward J774.1 cells. This NO inhibitory effect may directly correlate with antiinflammatory properties of the Netherlands propolis.

Inhibitory effects of caffeic acid phenethyl ester analogues on experimental lung metastasis of murine colon 26-L5 carcinoma cells.

We have previously examined the antiproliferative activity of caffeic acid phenethyl ester (CAPE) and its 20 analogues against six tumor cell lines, and found that CAPE analogues possess selective antiproliferative activity toward the murine colon 26-L5 carcinoma cell line. To extend our study, the effects of CAPE analogues on the metastatic development of murine colon 26-L5 carcinoma cells in the lung were examined. The oral administration of CAPE (5 mg/mice/d) for 7 d after tumor inoculation decreased the tumor weight and the number of tumor nodules in the lung by 50% and 50%, respectively, compared to the control, while CAPE (5 mg/mice/d) administered for 7 d before tumor inoculation showed no significant effect. Besides CAPE, 4-phenylbutyl caffeate, 8-phenyl-7-octenyl caffeate, 2-cyclohexylethyl caffeate and n-octyl caffeate at an oral dose of 2 mg/mice/d caused a 55%, 43%, 55% and 35% reduction of the tumor nodules in their lung metastasis formation, respectively. These results further elaborate the possibility of CAPE and its analogues to become a new class of chemopreventive agents for the treatment of colon cancer metastasis.

Selective antiproliferative activity of caffeic acid phenethyl ester analogues on highly liver-Metastatic murine colon 26-L5 carcinoma cell line

Caffeic acid phenethyl ester (CAPE, 2) and its twenty analogues ( 1, 3– 21) were prepared. These esters were tested by MTT assay on growth of murine colon 26-L5 carcinoma, murine B16-BL6 malonoma, murine Lewis lung carcinoma, human HT-1080 fibrosarcoma, human lung A549 adenocarcinoma, and human cervix HeLa adenocarcinoma cell lines. It was found that CAPE analogues possessed selective antiproliferative activity toward highly liver-metastatic murine colon 26-L5 carcinoma cell line. Among them, 4-phenylbutyl caffeate ( 4), ( Z)-8-phenyl-7-octenyl ( 10a) and ( E)-8-phenyl-7-octenyl ( 10b) caffeate showed the most potent antiproliferative activity (EC 50 value, 0.02 μM). In addition, CAPE ( 2) induced DNA fragmentation at concentrations of 1 to 10 μg/mL towards murine colon 26-L5 carcinoma cells.

Preferential cytotoxicity of caffeic acid phenethyl ester analogues on oral cancer cells

As part of our previous search for new compounds with improved biological activities including antibiotic, antiviral, anti-inflammatory, and tumor growth inhibition activities, we synthesized some caffeic acid phenethyl ester (CAPE)-like compounds from commercially available caffeic acid. Nine chemicals were tested by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay on the growth of buccal mucosal fibroblast (BF), oral submucosus fibroblast (OSF), neck metastasis of Gingiva carcinoma (GNM), and tongue squamous cell carcinoma (TSCCa) cells. CAPE and its ethyl analogue show significant cytotoxicity on OSF, GNM, and TSCCa cells, but not on BF cells. The results suggest that CAPE-like compounds may be potential chemotherapy agents against oral cancer.