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Inflammatory responses are orchestrated by a plethora of lipid mediators, and perturbations of their biosynthesis or degradation hinder resolution and lead to uncontrolled inflammation, which contributes to diverse pathologies. Small molecules that induce a switch from pro-inflammatory to anti-inflammatory lipid mediators are considered valuable for the treatment of chronic inflammatory diseases. Commonly used non-steroidal anti-inflammatory drugs (NSAIDs) are afflicted with side effects caused by the inhibition of beneficial prostanoid formation and redirection of arachidonic acid (AA) into alternative pathways. Multi-target inhibitors like diflapolin, the first dual inhibitor of soluble epoxide hydrolase (sEH) and 5-lipoxygenase-activating protein (FLAP), promise improved efficacy and safety but are confronted by poor solubility and bioavailability. Four series of derivatives bearing isomeric thiazolopyridines as bioisosteric replacement of the benzothiazole core and two series additionally containing mono- or diaza-isosteres of the phenylene spacer were designed and synthesized to improve solubility. The combination of thiazolo[5,4-b]pyridine, a pyridinylen spacer and a 3,5-Cl 2 -substituted terminal phenyl ring (46a) enhances solubility and FLAP antagonism, while preserving sEH inhibition. Moreover, the thiazolo[4,5-c]pyridine derivative 41b, although being a less potent sEH/FLAP inhibitor, additionally decreases thromboxane production in activated human peripheral blood mononuclear cells. We conclude that the introduction of nitrogen, depending on the position, not only enhances solubility and FLAP antagonism (46a), but also represents a valid strategy to expand the scope of application towards inhibition of thromboxane biosynthesis., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

Oxidative stress and inflammation are two conditions that coexist in many multifactorial diseases and the discovery of antioxidants is an attractive approach that can simultaneously tackle two or more therapeutic targets of the arachidonic acid cascade. We report that the simple structural variations on the 4-aryl-benzene-1,2-diol side-arm of the scaffold significantly influence the selectivity against 5-LOX vs 12- and 15-LOX. Derivatives 4 a-l were evaluated for their antioxidant activity, using the DPPH, and ferric ion reducing antioxidant power (FRAP) methods. Docking simulations proposed concrete binding of the catechol series to 5-LO. Selected active compound 4-(3,4-dihydroxyphenyl)dibenzofuran (4l) was also tested in different in vivo mouse models of inflammation. 4l (0.1 mg/kg; i.p.) impaired (I) bronchoconstriction in ovalbumin-sensitized mice challenged with acetylcholine, (II) exudate formation in carrageenan-induced paw edema, and (III) zymosan-induced leukocyte infiltration in air pouches. These results pave the way for investigating the therapeutic potential of 4-aryl-benzene-1,2-diol, as novel multitarget therapeutic drugs, able to regulate the complex inflammatory cascade mechanisms., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier Masson SAS.)

Endogenous long-chain metabolites of vitamin E (LCMs) mediate immune functions by targeting 5-lipoxygenase (5-LOX) and increasing the systemic concentrations of resolvin E3, a specialized proresolving lipid mediator. SAR studies on semisynthesized analogues highlight α-amplexichromanol ( 27a ), which allosterically inhibits 5-LOX, being considerably more potent than endogenous LCMs in human primary immune cells and blood. Other enzymes within lipid mediator biosynthesis were not substantially inhibited, except for microsomal prostaglandin E 2 synthase-1. Compound 27a is metabolized by sulfation and β-oxidation in human liver-on-chips and exhibits superior metabolic stability in mice over LCMs. Pharmacokinetic studies show distribution of 27a from plasma to the inflamed peritoneal cavity and lung. In parallel, 5-LOX-derived leukotriene levels decrease, and the inflammatory reaction is suppressed in reconstructed human epidermis, murine peritonitis, and experimental asthma in mice. Our study highlights 27a as an orally active, LCM-inspired drug candidate that limits inflammation with superior potency and metabolic stability to the endogenous lead.

Based on the significant anti-inflammatory activity of natural quinone primin (5a), series of 1,4-benzoquinones, hydroquinones, and related resorcinols were designed, synthesized, characterized and tested for their ability to inhibit the activity of cyclooxygenase (COX-1 and COX-2) and 5-lipoxygenase (5-LOX) enzymes. Structural modifications resulted in the identification of two compounds 5b (2-methoxy-6-undecyl-1,4-benzoquinone) and 6b (2-methoxy-6-undecyl-1,4-hydroquinone) as potent dual COX/5-LOX inhibitors. The IC 50 values evaluated in vitro using enzymatic assay were for compound 5b IC 50  = 1.07, 0.57, and 0.34 μM and for compound 6b IC 50  = 1.07, 0.55, and 0.28 μM for COX-1, COX-2, and 5-LOX enzyme, respectively. In addition, compound 6d was identified as the most potent 5-LOX inhibitor (IC 50  = 0.14 μM; reference inhibitor zileuton IC 50  = 0.66 μM) from the tested compounds while its inhibitory potential against COX enzymes (IC 50  = 2.65 and 2.71 μM for COX-1 and COX-2, respectively) was comparable with the reference inhibitor ibuprofen (IC 50  = 4.50 and 2.46 μM, respectively). The most important structural modification leading to increased inhibitory activity towards both COXs and 5-LOX was the elongation of alkyl chain in position 6 from 5 to 11 carbons. Moreover, the monoacetylation in ortho position of bromo-hydroquinone 13 led to the discovery of potent (IC 50  = 0.17 μM) 5-LOX inhibitor 17 (2-bromo-6-methoxy-1,4-benzoquinone) while bromination stabilized the hydroquinone form. Docking analysis revealed the interaction of compounds with Tyr355 and Arg120 in the catalytic site of COX enzymes, while the hydrophobic parts of the molecules filled the hydrophobic substrate channel leading up to Tyr385. In the allosteric catalytic site of 5-LOX, compounds bound to Tyr142 and formed aromatic interactions with Arg138. Taken together, we identified optimal alkyl chain length for dual COX/5-LOX inhibition and investigated other structural modifications influencing COX and 5-LOX inhibitory activity., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Masson SAS. All rights reserved.)

Inflammation contributes to the development of various pathologies, e.g. asthma, cardiovascular diseases, some types of cancer, and metabolic disorders. Leukotrienes (LT), biosynthesized from arachidonic acid by 5-lipoxygenase (5-LO), constitute a potent family of pro-inflammatory lipid mediators. δ-Garcinoic acid (δ-GA) (1), a natural vitamin E analogue, was chosen for further structural optimization as it selectively inhibited 5-LO activity in cell-free and cell-based assays without impairing the production of specialized pro-resolving mediators by 15-LO. A model of semi-quantitative prediction of 5-LO inhibitory potential developed during the current study allowed the design of 24 garcinamides that were semi-synthesized. In accordance with the prediction model, biological evaluations showed that eight compounds potently inhibited human recombinant 5-LO (IC 50  < 100 nM). Interestingly, four compounds were substantially more potent than 1 in activated primary human neutrophils assays. Structure - activity relationships shed light on a supplementary hydrophobic pocket in the allosteric binding site that could be fitted with an aromatic ring., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Masson SAS. All rights reserved.)

Leukotrienes (LTs) and prostaglandin (PG)E 2 , produced by 5-lipoxygenase (5-LO) and microsomal prostaglandin E 2 synthase-1 (mPGES-1), respectively, are key players in inflammation, and pharmacological suppression of these lipid mediators (LM) represents a strategy to intervene with inflammatory disorders. Previous studies revealed that the benzenesulfonamide scaffold displays efficient 5-LO-inhibitory properties. Here, we structurally optimized benzenesulfonamides which led to an N-phenylbenzenesulfonamide derivative (compound 47) with potent inhibitory activities (IC 50  = 2.3 and 0.4 μM for isolated 5-LO and 5-LO in intact cells, respectively). Compound 47 prevented the interaction of 5-LO with its activating protein (FLAP) at the nuclear envelope in transfected HEK293 cells as shown by in situ proximity ligation assay. Comprehensive assessment of the LM profile produced by human macrophages revealed the ability of 47 to selectively down-regulate pro-inflammatory LMs (i.e. LTs and PGE 2 ) in M1 but to enhance the formation of pro-resolving LMs (i.e. resolvins and maresins) in M2 macrophages. Moreover, 47 strongly inhibited LT formation and cell infiltration in two in vivo models of acute inflammation (i.e., peritonitis and air pouch sterile inflammation in mice). Together, 47 represents a novel LT biosynthesis inhibitor with an attractive pharmacological profile as anti-inflammatory drug that also promotes the biosynthesis of pro-resolving LM., (Copyright © 2018 Elsevier Masson SAS. All rights reserved.)

Geranyl flavones have been studied as compounds that potentially can be developed as anti-inflammatory agents. A series of natural geranylated flavanones was isolated from Paulownia tomentosa fruits, and these compounds were studied for their anti-inflammatory activity and possible mechanism of action. Two new compounds were characterized [paulownione C (17) and tomentodiplacone O (20)], and all of the isolated derivatives were assayed for their ability to inhibit cyclooxygenases (COX-1 and COX-2) and 5-lipoxygenase (5-LOX). The compounds tested showed variable degrees of activity, with several of them showing activity comparable to or greater than the standards used in COX-1, COX-2, and 5-LOX assays. However, only the compound tomentodiplacone O (20) showed more selectivity against COX-2 versus COX-1 when compared with ibuprofen. The ability of the test compounds to interact with the above-mentioned enzymes was supported by docking studies, which revealed the possible incorporation of selected test substances into the active sites of these enzymes. Furthermore, one of the COX/LOX dual inhibitors, diplacone (14) (a major geranylated flavanone of P. tomentosa), was studied in vitro to obtain a proteomic overview of its effect on inflammation in LPS-treated THP-1 macrophages, supporting its previously observed anti-inflammatory activity and revealing the mechanism of its anti-inflammatory effect.

Aiming to assess the biological activities of synthetic 1,4-benzoquinones, we previously synthesized different libraries of benzoquinones with lipophilic and bulky alkyl- or aryl-substituents that inhibited 5-lipoxygenase (5-LO). The high potency of 4,5-dimethoxy-3-alkyl-1,2-benzoquinones on 5-LO led to the idea to further modify the structures and thus to improve the inhibitory potential in vitro and in vivo as well as to investigate SARs. Systematic structural optimization through accurate structure-based design resulted in compound 30 (3-tridecyl-4,5-dimethoxybenzene-1,2-diol), an ubiquinol derivative that exhibited the strongest anti-inflammatory effect, with a 10-fold improved 5-LO inhibitory activity (IC 50  = 28 nM) in activated neutrophils. Moreover, 30 significantly reduced inflammatory reactions in the carrageenan-induced mouse paw oedema and in zymosan-induced peritonitis in mice. Compound 30 (1 mg/kg, i.p.) potently suppressed the levels of cysteinyl-LTs 30 min after zymosan, outperforming zileuton at a dose of 10 mg/kg. The binding patterns of the quinone- and hydroquinone-based 5-LO inhibitors were analyzed by molecular docking. Together, we elucidated the optimal alkyl chain pattern of quinones and corresponding hydroquinones and reveal a series of highly potent 5-LO inhibitors with effectiveness in vivo that might be useful as anti-inflammatory drugs., (Copyright © 2016 Elsevier Masson SAS. All rights reserved.)

5-Lipoxygenase (5-LO) catalyzes the first two steps in leukotriene (LT) biosynthesis. Because LTs play pivotal roles in allergy and inflammation, 5-LO represents a valuable target for anti-inflammatory drugs. Here, we investigated the molecular mechanism, the pharmacological profile, and the in vivo effectiveness of the novel 1,2-benzoquinone-featured 5-LO inhibitor RF-22c. Compound RF-22c potently inhibited 5-LO product synthesis in neutrophils and monocytes (IC50⩾22nM) and in cell-free assays (IC50⩾140nM) without affecting 12/15-LOs, cyclooxygenase (COX)-1/2, or arachidonic acid release, in a specific and reversible manner, supported by molecular docking data. Antioxidant or iron-chelating properties were not evident for RF-22c and 5-LO-regulatory cofactors like Ca(2+) mobilization, ERK-1/2 activation, and 5-LO nuclear membrane translocation and interaction with 5-LO-activating protein (FLAP) were unaffected. RF-22c (0.1mg/kg; i.p.) impaired (I) bronchoconstriction in ovalbumin-sensitized mice challenged with acetylcholine, (II) exudate formation in carrageenan-induced paw edema, and (III) zymosan-induced leukocyte infiltration in air pouches. Taken together, RF-22c is a highly selective and potent 5-LO inhibitor in intact human leukocytes with pronounced effectiveness in different models of inflammation that warrants further preclinical analysis of this agent as anti-inflammatory drug., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Embelin (2,5-dihydroxy-3-undecyl-1,4-benzoquinone) possesses anti-inflammatory and anti-carcinogenic properties in vivo, and these features have been related to interference with multiple targets including XIAPs, NFκB, STAT-3, Akt and mTOR. However, interference with these proteins requires relatively high concentrations of embelin (IC₅₀>4 μM) and cannot fully explain its bioactivity observed in several functional studies. Here we reveal human 5-lipoxygenase (5-LO) and microsomal prostaglandin E₂ synthase (mPGES)-1 as direct molecular targets of embelin. Thus, embelin potently suppressed the biosynthesis of eicosanoids by selective inhibition of 5-LO and mPGES-1 with IC₅₀=0.06 and 0.2 μM, respectively. In intact human polymorphonuclear leukocytes and monocytes, embelin consistently blocked the biosynthesis of various 5-LO products regardless of the stimulus (fMLP or A23187) with IC₅₀=0.8-2 μM. Neither the related human 12- and 15-LO nor the cyclooxygenases-1 and -2 or cytosolic phospholipase A₂ were significantly affected by 10 μM embelin. Inhibition of 5-LO and mPGES-1 by embelin was (I) essentially reversible after wash-out, (II) not impaired at higher substrate concentrations, (III) unaffected by inclusion of Triton X-100, and (IV) did not correlate to its proposed antioxidant properties. Docking simulations suggest concrete binding poses in the active sites of both 5-LO and mPGES-1. Because 5-LO- and mPGES-1-derived eicosanoids play roles in inflammation and cancer, the interference of embelin with these enzymes may contribute to its biological effects and suggests embelin as novel chemotype for development of dual 5-LO/mPGES-1 inhibitors., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Quinones are compounds frequently contained in medicinal plants used for the treatment of inflammatory diseases. Therefore, the impact of plant-derived quinones on the arachidonic acid metabolic pathway is worthy of investigation. In this study, twenty-three quinone compounds of plant origin were tested in vitro for their potential to inhibit leukotriene B4 (LTB4) biosynthesis in activated human neutrophil granulocytes with 5-lipoxygenase (5-LOX) activity. The benzoquinones primin (3) and thymohydroquinone (4) (IC50 = 4.0 and 4.1 microM, respectively) showed activity comparable with the reference inhibitor zileuton (1C50 = 4.1 microM). Moderate activity was observed for the benzoquinone thymoquinone (2) (1C50 = 18.2 microM) and the naphthoquinone shikonin (1) (IC50 = 24.3 microM). The anthraquinone emodin and the naphthoquinone plumbagin (5) displayed only weak activities (IC50 > 50 microM). The binding modes of the active compounds were further evaluated in silico by molecular docking to the human 5-LOX crystal structure. This process supports the biological data and suggested that, although the redox potential is responsible for the quinone's activity on multiple targets, in the case of 5-LOX the molecular structure plays a vital role in the inhibition. The obtained results suggest primin as a promising compound for the development of dual COX-2/5-LOX inhibitors.