Novel dual inhibitors of 5-lipoxygenase and thromboxane A2 synthetase: synthesis and structure-activity relationships of 3-pyridylmethyl-substituted 2-amino-6-hydroxybenzothiazole derivatives

Classification models and SAR analysis on thromboxane A2 synthase inhibitors by machine learning methods

Thromboxane A2 synthase (TXS) is a promising drug target for cardiovascular diseases and cancer. In this work, we conducted a structure-activity relationship (SAR) study on 526 TXS inhibitors for bioactivity prediction. Three types of descriptors (MACCS fingerprints, ECFP4 fingerprints, and MOE descriptors) were utilized to characterize inhibitors, 24 classification models were developed by support vector machine (SVM), random forest (RF), extreme gradient boosting (XGBoost), and deep neural networks (DNN). Then we reduced the number of fingerprints according to the contribution of descriptors to the models, and constructed 16 extra models on simplified fingerprints. In general, Model_4D built by DNN algorithm and 67 bits MACCS fingerprints performs best. The prediction accuracy of the model on the test set is 0.969, and Matthews correlation coefficient (MCC) is 0.936. The distance between compound and model (dSTD-PRO) was used to characterize the application domain of the model. In the test set of Model_4D, dSTD-PRO of 91.5% compounds is lower than the corresponding training set threshold (threshold0.90 = 0.1055), and the accuracy of these compounds is 0.983. In addition, the important descriptors were summarized and further analyzed. It showed that aromatic nitrogenous heterocyclic groups were beneficial to improve the bioactivity of TXS inhibitors.

Catalyst-dependent chemoselective insertion of diazoalkanes into N-H\C-H\O-H\C-O bonds of 2-hydroxybenzothiazoles

The control of chemoselective insertions of diazoalkanes with 2-hydroxybenzothiazoles is challenging. Herein, the chemoselective N-H, O-H, C-O or C-H bond insertions of diazoalkanes with 2-hydroxybenzothiazoles are achieved using B(C6F5)3, Rh2(OAc)4...

Structural Activity Relationship and Importance of Benzothiazole Derivatives in Medicinal Chemistry: A Comprehensive Review

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Benzothiazole (1, 3-benzothiazole) is one of the heterocyclic compounds, which is a weak base having varied biological activities. The unique methine center present in the thiazole ring makes benzothiazole as the most important heterocyclic compound. It is a common and integral structure of many natural and synthetic bioactive molecules. Benzothiazole derivatives show a variety of activities, with less toxic effects and their derivatives showed enhanced activities, which has proven Benzothiazole scaffold as one of the important moieties in medicinal chemistry. Benzothiazole ring containing compounds possess various pharmacological activities such as anti-viral, anti-microbial, antiallergic, anti-diabetic, anti-tumor, anti-inflammatory, anthelmitic and anti-cancer, which makes benzothiazole a rapidly developing and interesting compound in the medicinal chemistry. This review briefly explains the importance, common methods of synthesis of the benzothiazole scaffold and also explains the popular benzothiazole molecules which have applications in various fields of chemistry. A review has been carried out based on various pharmacological activities containing benzothiazole moieties and rationalize the activities based on the structural variations. Literature on benzothiazole derivatives reveals that substitution on the C-2 carbon atom and C-6 are the reasons for a variety of biological activities.

Multiple target-centric strategy to tame inflammation

Single-target inhibition is an unsatisfactory therapeutic option to treat multifactorial pathologies, brought into limelight 'paradox of inflammation' beside dearth of innovation, rationalizes a shift toward 'multiple-target' design concept in anti-inflammatory research field. To improvise, two platform strategies, drugs mixture or multitarget drugs, are plausible. Dual cyclooxygenase/lipoxygenase inhibitor 'licofelone' developed after the backfire of rofecoxib due to safety concerns has fetched first light of triumph of the latter strategy. As hitting multiple targets in restraint is perhaps more viable strategy rather than single target, this review, outlines the most germane multiple target agents of synthetic and natural origin placing clear advantage in favors of multitarget strategy as real therapeutic solution for inflammation.

Design, synthesis and biological evaluation of benzimidazole/benzothiazole and benzoxazole derivatives as cyclooxygenase inhibitors

We have synthesised a series of 2-[[2-alkoxy-6-pentadecylphenyl)methyl]thio]-1H-benzimidazoles/benzothiazoles and benzoxazoles from anacardic acid and investigated their ability to inhibit human cyclooxygenase-2 enzyme (COX-2). The active compounds were screened for cyclooxygenase-1 (COX-1) inhibition. Compound 13 is 384-fold and 19 is more than 470-fold selective towards COX-2 compared to COX-1. Thus, this class of compounds may serve as excellent candidates for selective COX-2 inhibition.

E3040 sulphate, a novel thromboxane synthase inhibitor, blocks the Cl- secretion induced by platelet-activating factor in isolated rat colon

1. E3040 (6-hydroxy-5,7-dimethyl-2-methylamino-4-(3-pyridylmethyl)benzothiazole), is a novel dual inhibitor of 5-lipoxygenase (5-LOX) and thromboxane synthase (Tx synthase). Here, we examined the effects of E3040 sulphate, a sulphate conjugate of E3040, on these enzyme activities in cell-free systems and on the thromboxane A2 (TxA2)-mediated Cl- secretion induced by platelet-activating factor (PAF) in isolated rat colons. 2. E3040 sulphate inhibited Tx synthase activity in a concentration-dependent manner (IC50=0.013 microM), whereas it induced little effects on 5-LOX and cyclo-oxygenase activities (IC50>100 microM) with the cell-free enzyme assay. 3. With isolated rat colonic mucosa, E3040 sulphate in a concentration-dependent manner (IC50=1.8 microM) inhibited the Cl- secretion induced by 10 microM PAF. On the other hand, E3040 sulphate (30 microM) induced no effect on the prostaglandin E2 (0.5 microM)- and leukotriene D4 (1 microM)-induced Cl- secretion in the colon. 4. PAF (10 microM) increased a release of TxB2, a stable metabolite of TxA2, from the colonic mucosa. This increase was significantly inhibited by subsequent addition of E3040 sulphate (30 microM). 5. Probenecid (100 microM), an inhibitor of organic anion transporter, abolished the inhibitory effect of E3040 sulphate on the PAF-induced Cl- secretion. Another inhibitor, sulphobromophthalein (30 microM) partially but significantly attenuated the effect of E3040 sulphate. p-aminohippuric acid (1 mM) had no effect. 6. These findings suggest that E3040 sulphate is a novel Tx synthase inhibitor, and that E3040 sulphate taken up into the colonic cells by organic anion transporters inhibits the PAF-induced Cl- secretion by blocking a release of TxA2.

Effect of E3040, an inhibitor of 5-lipoxygenase and thromboxane synthase, on rat bowel damage induced by lipopolysaccharide

Intravenous administration of lipopolysaccharide to rats that had been immunized with lipopolysaccharide induced hemorrhagic damage in the large intestine. We investigated the role of 5-lipoxygenase and thromboxane synthase products in the damage of the large intestine induced by lipopolysaccharide. In the large intestine of lipopolysaccharide-immunized rats, intravenous injection of lipopolysaccharide increased the vascular permeability, production of leukotriene B(4), leukotriene C(4)/D(4), thromboxane B(2) and prostaglandin E(2), and also increased the activity of myeloperoxidase, a marker enzyme of neutrophils. Oral administration of E3040 (6-hydroxy-5,7-dimethyl-2-(methylamino)-4-(3-pyridylmethyl)benzothiazole), a novel dual inhibitor of 5-lipoxygenase and thromboxane synthase, at 30 and 100 mg/kg inhibited the increase in vascular permeability induced by lipopolysaccharide in the large intestine. E3040 inhibited the production of leukotriene B(4) and thromboxane B(2) and tended to increase the production of prostaglandin E(2) in the large intestine. Sulfasalazine (500 mg/kg) and prednisolone (10 mg/kg), drugs used for the treatment of inflammatory bowel disease, had no significant effect on eicosanoid production and vascular permeability. These results indicate that E3040 inhibits the production of both leukotriene B(4) and thromboxane B(2) and prevents lipopolysaccharide-induced damage in the large intestine of lipopolysaccharide-immunized rats.

In vitro effects of E3040, a dual inhibitor of 5-lipoxygenase and thromboxane A(2) synthetase, on eicosanoid production

In vitro pharmacological profiles of E3040, 6-hydroxy-5, 7-dimethyl-2-(methylamino)-4-(3-pyridylmethyl) benzothiazole were investigated. Against the 5-lipoxygenase activity of rat basophilic leukemia cells, E3040 and zileuton (a 5-lipoxygenase inhibitor) had an IC(50) of 0.23 and 0.93 microM, respectively. Against the thromboxane A(2) synthetase activity of human platelets, E3040 had an IC(50) of 0.01 microM, which was comparable to that of OKY-1581 (sodium (E)-3-[4-(3-pyridylmethyl) phenyl]-2-methylacrylate, a thromboxane A(2) synthetase inhibitor). Against cyclooxygenase activity of sheep seminal vesicles, E3040 showed no inhibition (IC(50), >300 microM). Sulfasalazine and 5-aminosalicylic acid, therapeutic drugs for inflammatory bowel disease, inhibited 5-lipoxygenase activity with an IC(50) of 293 and 970 microM, respectively. Sulfasalazine inhibited thromboxane A(2) synthetase activity with an IC(50) of 20 microM. In rat peritoneal leukocytes, E3040 inhibited leukotriene B(4) and thromboxane B(2) production with an IC(50) of 0.17 and 0.24 microM, respectively. E3040 inhibited leukotriene B(4) production in human neutrophils and thromboxane B(2) production in human platelets (IC(50) of 0.21 and 0.09 microM, respectively). These results indicated that E3040 potently inhibited 5-lipoxygenase and thromboxane A(2) synthetase and blocked leukotriene B(4) and thromboxane B(2) production in rat peritoneal and human blood cells.

Desulfonation of a colitis inducer 2,4,6-trinitrobenzene sulfonic acid produces sulfite radical

2,4,6-Trinitrobenzene sulfonic acid (TNBS) has been used in vivo to induce colitis. With the nitroreductase of intestinal cells, TNBS underwent redox cycling to produce TNBS-nitro and superoxide radical anions which are thought to be involved in initial oxidative reactions that lead to colonic injury. In this study, we demonstrated that the TNBS desulfonative reaction with tissue amino acids produces sulfite which is subsequently oxidized to sulfite radical. Sulfite radical was measured using a spin trapping methodology. Sulfite radical adducts of 5,5-dimethyl-1-pyrroline N-oxide (DMPO) or 5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide (DEPMPO) were detected in a mixture of TNBS and lysine, xanthine oxidase, red blood cells, colonic mucosal or submucosal muscle tissues. TNBS alone did not produce sulfite radical, indicating that its formation required the presence of amino acids. Because sulfite radical is the precursor of highly reactive sulfiteperoxyl and sulfate radicals, our data imply that these sulfite-derived free radicals may also contribute to oxidative reactions leading to colonic injury in TNBS-induced colitis.

Generation of nitro and superoxide radical anions from 2,4,6-trinitrobenzenesulfonic acid by rat gastrointestinal cells

Reactive oxygen and nitrogen species have been implicated in the inflammation of the gastrointestinal tract. The objective of this study was to investigate mechanisms of free radical formation from the colitis inducer 2,4,6-trinitrobenzene sulfonic acid (TNBS). We showed that TNBS was rapidly metabolized to TNBS nitro radical anion via metabolic reduction by flavinmononucleotide/NADPH, xanthine/xanthine oxidase as well as the rat small intestine and colon. TNBS nitro radical anion was directly detected with electron paramagnetic resonance (EPR) spectroscopy. EPR spectra of TNBS nitro radical anion showed hyperfine coupling constants from the proximal nitrogen, two hydrogens and the two distal nitrogens with respective magnitudes of a(N)(4) = 9.7 G; a(H)(3,5) = 3.2 G (2); and a(N)(2,6) = 0.25 G. EPR spin trapping using 5.5-dimethyl-1-pyrroline N-oxide in aerobic incubations of isolated enterocytes (or colonocytes, or red blood cells) and TNBS, in the presence or absence of NADPH, produced radical adducts characteristic of superoxide and hydroxyl radicals. Our EPR data showing generation of TNBS nitro and superoxide radical anions demonstrate that one-electron reduction of TNBS may be an initial step in the cascade of the in vivo inflammatory events in TNBS-induced colitis.

Expression of glutathione S-transferases Ya, Yb1, Yb2, Yc1 and Yc2 and microsomal epoxide hydrolase genes by thiazole, benzothiazole and benzothiadiazole

The effects of thiazole (TH), benzothiazole (BT) and benzothiadiazole (BZ) on the expression of hepatic glutathione S-transferases (GSTs) Ya, Yb1, Yb2, Yc1 and Yc2 and microsomal epoxide hydrolase (mEH) genes were compared in rats. TH treatment resulted in 4- to 24-fold increases in GST Ya mRNA levels at 24 hr posttreatment; the ED50 value was 70 mg/kg. GST Ya mRNA levels were elevated 13-, 20-, 20- and 9-fold at 12, 24, 48 and 72 hr following 100 mg/kg of TH treatment, respectively, as compared with the control. BT was a moderate inducer of GST Ya with a maximal 18-fold increase observed, whereas BZ treatment caused a transient increase in GST Ya mRNA at 12 hr posttreatment, followed by a return to a 4-fold relative increase at 24 hr or afterward. Treatment of rats with TH at the dose of 100 mg/kg resulted in an approximately 10-fold increase in either Yb1 or Yb2 mRNA levels at 24 hr posttreatment. BT-treated rats showed 7- and 3-fold increases in the GST subunit Yb1 and Yb2 mRNA levels at 24 hr posttreatment. BZ was the least effective in modulating either GST Yb1 or Yb2 mRNA, resulting in < 2-fold changes. GST Yc1 and Yc2 mRNA levels were increased approximately 8-fold at the dose of 200 mg/kg of TH. BT minimally affected GST subunit Yc1 and Yc2 mRNA levels, with a maximal 4-fold relative increase observed. BZ was the least effective in enhancing Yc1 and Yc2 mRNA levels. Protein levels for GST subunit Ya, Yb1, Yb2 and Yc were also elevated in response to TH by 3-, 2-, 2-, and 2-fold, respectively. Thus, TH was effective in modulating both constitutive and inducible GST gene expression. BT or BZ was much less effective in increasing the expression of GST subunits. These RNA and Western blot analyses revealed that the levels of major GST were differentially increased after treatment with these thiazoles, exhibiting a rank order of GST expression of TH > BT > BZ. mEH expression by these compounds appeared to be consistent with that of GST Ya. The mRNA levels for GST Ya, Yb1, Yb2, Yc1 and Yc2 and mEH were also determined after treatment with triazole (TR), imidazole (IM), benzoxazole (BX), benzotriazole (BTR) or benzimidazole (BIM). TR, IM, BX or BTR caused increases in Ya, Yb1, Yc1 and Yc2 mRNA levels by 2- to 3-fold, whereas the agents failed to modulate the expression of GST Yb2. The fact that benzene, cyclohexane or n-hexane minimally affected the major GST or mEH mRNA levels provided evidence that certain heterocyclic compounds are more capable of modulating GST or mEH gene expression than hydrocarbons. These results corroborate evidence that the thiazoles differentially stimulate GST or mEH genes, with TH being the most efficacious; that thiazoles with carbocyclic ring are much less effective in increasing GST or mEH levels than is TH; and that the changes in these GST and mEH levels are primarily associated with increases in mRNA levels.

Structure-activity relationships of (E)-3-(1,4-benzoquinonyl)-2-[(3-pyridyl)-alkyl]-2-propenoic acid derivatives that inhibit both 5-lipoxygenase and thromboxane A2 synthetase

As part of our research for the development of novel antiinflammatory drug candidates, we have designed and synthesized a series of (E)-3-(1,4-benzoquinonyl)-2-[(3-pyridyl)alkyl]-2-propenoic acid derivatives as dual inhibitors of 5-lipoxygenase (5-LO) and thromboxane (TX) A2 synthetase. In order to increase the absorption after oral administration, we introduced a carboxylic acid moiety into the 1,4-benzoquinone skeleton, which has 5-LO-inhibitory character. Introduction of a 3-pyridylalkyl group at the double bond of the 1,4-benzoquinonyl propenoic acid moiety afforded good to moderate inhibitory activities against the production of leukotriene (LT) B4 and TXA2 while not significantly inhibiting that of prostaglandin E2 by glycogen-induced peritoneal cells of rat (in vitro). The length of the methylene chain of the 3-pyridylalkyl group influenced the inhibition of LTB4 and TXB2 production. An increase of lipophilicity by introducing a more lipophilic alkoxy group did not markedly increase the inhibitory activity on LTB4 production. The position of alkoxy group on the 1,4-benzoquinone skeleton played an important role in TXA2 synthetase inhibition. Compounds such as 20c (E6700) with an appropriate alkoxy group and proper length of methylene side chain, together with a polar substituent (carboxylic acid), showed good inhibition of both 5-LO and TXA2 synthetase and possess a variety of pharmacologically beneficial effects.