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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 0.11 µM, 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.

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Given the hepatotoxicity and an unfavorable pharmacokinetic profile of zileuton (Zyflo® ), currently the only approved and clinically used 5-Lipoxygenase (5-LO) inhibitor, the search for potent and safe 5-LO inhibitors is highly demanded. The action of several phenolic acid phenethyl esters as potential 5-Lipoxygenase (5-LO) inhibitors has been investigated. For this purpose, a series of 14 phenethyl esters was synthesized and their impact on 5-LO inhibition was evaluated. The effects of position and number of hydroxyl and methoxy groups on the phenolic acid were investigated. The shortening of the linker between the carbonyl and the catechol moiety as well as the presence of the α,ß-unsaturated carbonyl group was also explored. The sinapic acid phenethyl ester (10), which can be named SAPE (10) by analogy to caffeic acid phenethyl ester (CAPE), inhibited 5-LO in a concentration-dependent manner and outperformed both zileuton (1) and CAPE (2). With an IC50 of 0.3 µm, SAPE (10) was threefold more potent than CAPE (2) and 10-fold more potent than zileuton (1), the only 5-LO inhibitor approved for clinical use. Unlike CAPE (2), SAPE (10) had no effect on 12-lipoxygenase (12-LO) and less effect on cyclooxygenase 1 (COX-1) which makes it a more selective 5-LO inhibitor.

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Leukotrienes (LTs) are a class of lipid mediators implicated in numerous inflammatory disorders. Caffeic acid phenethyl ester (CAPE) possesses potent anti-LTs activity through the inhibition of 5-lipoxygenase (5-LO), the key enzyme in the biosynthesis of LTs. In this study, we describe the design and synthesis of CAPE analogs as radical scavengers and 5-LO inhibitors. Caffeic esters bearing propargyl and allyl linkers between the caffeoyl and aryl moieties (4a-i and 5a-i, respectively) were synthesized by Sonogashira and Heck cross-coupling reactions to probe the effects of flexibility and aryl substitution on 5-LO inhibition. Caffeoyl alcohol and ethers (6, 7a-b) as well as caffeoyl aldehyde and ketones (8a-e) were synthesized to elucidate the importance of the ester linkage for inhibitory activity. All tested compounds proved to be good radical scavengers (IC50 of 10-30 µm). After preliminary anti-LTs activity screening in HEK293 cell models, 5-LO inhibition potential of selected compounds was determined in human polymorphonuclear leukocytes (PMNL). Most screened compounds outperformed CAPE 3 in concentration-dependent assays on PMNL, with ester dimers 4i and 5i along with caffeoyl ethers 7a-b being roughly eight-, seven-, and 16-fold more potent than Zileuton, with IC50 values of 0.36, 0.43, and 0.18 µm, respectively.

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Two novel boron compounds containing caffeic acid phenethyl ester (CAPE) derivatives have been prepared and characterized fully. These new compounds and CAPE have been investigated for potential antioxidant and antimicrobial properties and their ability to inhibit 5-lipoxygenase and whether chelation to boron improves their biological activity. Sodium salt 4 was generally more active than ammonium salt 5 in the biological assays and surpassed the radical scavenging ability of CAPE. Compounds 4 and 5 were more active than CAPE and Zileuton in human polymorphonuclear leukocytes. These results clearly show the effectiveness of the synthesized salts as transporter of CAPE.

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Caffeic acid and its naturally occurring derivative caffeic acid phenethyl ester (CAPE) have antiproliferative and cytotoxic properties in a variety of cancer cell lines without displaying significant toxicity toward healthy cells, and are considered to be potential anticancer agents. However, little is known about their effects on prostate cancer cells. We synthesized and evaluated the effects of caffeic acid, CAPE (2) and 18 synthetic derivatives on cell viability and androgen-dependent cell proliferation, subcellular localisation and expression of androgen receptor (AR) and secretion of prostate-specific antigen (PSA) in LNCaP human hormone-dependent prostate cancer cells. Several synthetic derivatives of CAPE were strong, concentration-dependent cytotoxic agents in LNCaP cells with IC50 values in the 6.8-26.6 µM range, potencies that were up to five-fold greater than that of CAPE (33.7±4.0 µM). A number of caffeic acid derivatives were inhibitors of androgen-stimulated LNCaP cell proliferation with concomitant inhibition of DHT-stimulated PSA secretion. Compound 24 was the most cytotoxic and antiproliferative caffeic acid derivative (IC50 values of 6.8±0.3 and 2.4±0.8 µM, respectively) inhibiting DHT-stimulated cell proliferation and PSA secretion statistically significantly at concentrations as low as 0.3 µM. Exposure to DHT increased cytoplasmic and nuclear AR levels and co-treatment with increasing concentrations of compound 24 or CAPE (2), notably, further increased these levels. In conclusion, a number of synthetic derivatives of caffeic acid are potent inhibitors of androgen-dependent prostate cancer cell proliferation and viability, acting, at least in part, via an antiandrogenic mechanism that involves increased nuclear accumulation of (presumably inactive) AR.

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Changes across metabolic networks are emerging as an integral part of cancer development and progression. Increasing comprehension of the importance of metabolic processes as well as metabolites in cancer is stimulating exploration of novel, targeted treatment options. Arachidonic acid (AA) is a major component of phospholipids. Through the cascade catalyzed by cyclooxygenases and lipoxygenases, AA is also a precursor to cellular signaling molecules as well as molecules associated with a variety of diseases including cancer. 5-Lipoxygenase catalyzes the transformation of AA into leukotrienes (LT), important mediators of inflammation. High-throughput analysis of metabolic profiles was used to investigate the response of glioblastoma cell lines to treatment with 5-lipoxygenase inhibitors. Metabolic profiling of cells following drug treatment provides valuable information about the response and metabolic alterations induced by the drug action and give an indication of both on-target and off-target effects of drugs. Four different 5-lipoxygenase inhibitors and antioxidants were tested including zileuton, caffeic acid, and its analogues caffeic acid phenethyl ester and caffeic acid cyclohexethyl ester. A NMR approach identified metabolic signatures resulting from application of these compounds to glioblastoma cell lines, and metabolic data were used to develop a better understanding of the mode of action of these inhibitors.

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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.

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