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,β-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 IC 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.

Solvent-free catalytic hydrogenation of pinene over Pd on carbon, alumina, and silica supports were compared. Despite the absence of solvent, Pd catalyst on all three supports yields to a quantitative conversion of pinene to pinanes and a higher selectivity for the cis isomer (72−89%). The temperature affected similarly the selectivity of the reaction for all three catalysts in favor of the cis-pinane isomer. However, recycling of the Pd on the three tested supports varied greatly. If Pd/C and Pd/alumina were successfully recycled 13 and 14 times, respectively, Pd/silica could be used only once to convert pinenes into pinanes. Remaining very effective during all 13 cycles, Pd/C was the best catalyst/support of the three tested ones for the solvent-free hydrogenation of pinene. The influence of H 2 pressure on pinene conversion rates were investigated for Pd/C catalyst. An extremely low leaching rate of palladium in pinenes and pinanes determined by ICP/MS confirmed the heterogeneous nature of this catalytic solvent-free reaction. The hydrogenation reaction presented in this paper is an alternate environmentally friendly pathway for pinane synthesis.

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 (IC 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 IC values of 0.36, 0.43, and 0.18 μm, respectively.

5-Lipoxygenase (5-LO) is the key enzyme responsible for the conversion of arachidonic acid to leukotrienes, a class of lipid mediators implicated in inflammatory disorders. In this paper, we describe the design, synthesis, and preliminary activity studies of novel clicked caffeic esters and amides as radical scavengers and 5-LO inhibitors. From known 5-LO inhibitor 3 as a lead, cinnamic esters 8a–h and amides 9a–h as well as caffeic esters 15a–h and amides 16a–h were synthesized by Cu(I)-catalyzed [1,3]-dipolar cycloaddition with the appropriate azide precursors and terminal alkynes. All caffeic analogs are proved to be good radical scavengers (IC50: 10–20 μM). Esters 15g and 15f possessed excellent 5-LO inhibition activity in HEK293 cells and were equipotent with the known 5-LO inhibitor CAPE and more potent than Zileuton. Several synthesized esters possess activities rivaling Zileuton in stimulated human polymorphonuclear leukocytes.

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.