Effect of a new squalene synthase inhibitor on an ApoE-/- mouse model of atherosclerosis

Ηypercholesterolemia/hyperlipidemia in conjunction with oxidative stress and inflammatory processes contribute synergistically to the pathogenesis of atherosclerosis. We hereby evaluated the antiatherosclerotic effect of the multi-target derivative 4-methyl-2-(10H-phenothiazin-3-yl)morpholin-2-ol hydrobromide 1 in apoE^-/- mice; compound 1 is a potent antihyperlipidemic agent acting through Squalene Synthase inhibition, while it has exhibited an outstanding antioxidant and anti-inflammatory activity in various experimental animal models. The new analogue was evaluated in terms of its antiatherosclerotic/antioxidant effect in the ApoE^-/- transgenic mouse model. Its toxicity profile was also assessed by measuring the levels of four sensitive indicators of liver toxicity. Prolonged administration of 1 in ApoE^-/- mice fed with a western-type (wt) diet efficiently reduced the aortic atheromatic lesions, an effect that took place through a cholesterol lowering independent manner. In addition, 1 displayed a significant reduction not only of glucose but also of oxidative stress levels, while it did not cause any toxicity. To the best of our knowledge this is the first time that the antiatherosclerotic effect of a Squalene Synthase inhibitor is studied in this specific atherosclerosis mouse model. As a result, compound 1 may serve as a promising starting point towards developing new bioactive analogues against the onset and subsequent development of atherosclerosis.

Design of Improved Antidiabetic Drugs: A Journey from Single to Multitarget Agents

Multifactorial diseases exhibit a complex pathophysiology with several factors contributing to their pathogenesis and development. Examples of such disorders are neurodegenerative (e. g. Alzheimer's, Parkinson's) and cardiovascular diseases (e. g. atherosclerosis, metabolic syndrome, diabetes II). Traditional therapeutic approaches with single-target drugs have been proven, in many cases, unsatisfactory for the treatment of multifactorial diseases such as diabetes II. The well-established by now strategy of multitarget drugs is constantly gaining interest and momentum, as a more effective approach. The development of pharmacomolecules able to simultaneously modulate multiple relevant-to-the-disease targets has already several successful examples in various fields and has, as such, inspired the design of multitarget antidiabetic agents; this review highlights the design aspect and efficacy of this approach for improved antidiabetics by presenting several examples of successful pharmacophore combinations in (multitarget) agents that modulate two or more molecular targets involved in diabetes II, resulting in a superior antihyperglycemic profile.

New applications of squalene synthase inhibitors: Membrane cholesterol as a therapeutic target

Squalene synthase (SQS) inhibitors, mostly known as antihyperlipidemic agents for controlling blood cholesterol levels, have been increasingly used to study alterations of the cholesterol content in cell membranes. As such, SQS inhibitors have been demonstrated to control cellular activities related to cancer cell proliferation and migration, neuron degeneration, and parasite growth. While the mechanisms behind the effects of cellular cholesterol are still being revealed in detail, the evidence for SQS as a therapeutic target for several seemingly unrelated diseases is increasing. SQS inhibitors may be the next promising candidates targeting the three remaining primary therapeutic areas, beyond cardiovascular disease, which still need to be addressed; their application as anticancer, antimicrobial, and antineurodegenerative agents appears promising for new drug discovery projects underway.

Morpholine As a Scaffold in Medicinal Chemistry: An Update on Synthetic Strategies

Morpholine is a frequently used heterocycle in medicinal chemistry and a privileged structural component of bioactive molecules. This is mainly due to its contribution to a plethora of biological activities as well as to an improved pharmacokinetic profile of such bioactive molecules. The synthesis of morpholines is a subject of much study due to their biological and pharmacological importance, with the last such review being published in 2013. Here, an overview of the main approaches toward morpholine synthesis or functionalization is presented, emphasizing on novel work which has not been reviewed so far. This review is an update on synthetic strategies leading to easily accessible libraries of bioactives which are of interest for drug discovery projects.

Morpholine as a privileged structure: A review on the medicinal chemistry and pharmacological activity of morpholine containing bioactive molecules

Morpholine is a heterocycle featured in numerous approved and experimental drugs as well as bioactive molecules. It is often employed in the field of medicinal chemistry for its advantageous physicochemical, biological, and metabolic properties, as well as its facile synthetic routes. The morpholine ring is a versatile and readily accessible synthetic building block, it is easily introduced as an amine reagent or can be built according to a variety of available synthetic methodologies. This versatile scaffold, appropriately substituted, possesses a wide range of biological activities. There are many examples of molecular targets of morpholine bioactive in which the significant contribution of the morpholine moiety has been demonstrated; it is an integral component of the pharmacophore for certain enzyme active-site inhibitors whereas it bestows selective affinity for a wide range of receptors. A large body of in vivo studies has demonstrated morpholine's potential to not only increase potency but also provide compounds with desirable drug-like properties and improved pharamacokinetics. In this review we describe the medicinal chemistry/pharmacological activity of morpholine derivatives on various therapeutically related molecular targets, attempting to highlight the importance of the morpholine ring in drug design and development as well as to justify its classification as a privileged structure.

Optimizing the Pharmacological Profile of New Bifunctional Antihyperlipidemic/Antioxidant Morpholine Derivatives

Among the causal risk factors directly promoting the development of coronary and peripheral atherosclerosis are reactive oxygen species and elevated low-density lipoprotein plasma levels. We hereby designed new potent squalene synthase (SQS) inhibitors that may simultaneously tackle the oxidative stress induced by lipid peroxidation. Using previously developed morpholine derivatives as a starting point, we conducted extensive structural changes by either substituting or modifying the morpholine ring, aiming at an optimal SQS-antioxidant pharmacological profile. Compounds 2, 3, and 7 emerged as the most potent bifunctional analogues, displaying IC₅₀ values for SQS inhibition of 0.014, 0.16, and 0.51 μΜ, respectively, and further significantly decreasing lipid peroxidation of hepatic microsomal membranes. The aforementioned activities were also confirmed in vivo since the most promising derivative 2 exhibited a remarkable antihyperlipidemic and antioxidant effect. In conclusion, rational drug design accompanied by structure-activity relationship studies led to compounds combining improved antioxidant and antihyperlipidemic activity that may serve as multifunctional agents against atherosclerosis.

Synthesis of quinoline/naphthalene-containing azaphenothiazines and their potent in vitro antioxidant properties

New tetracyclic and pentacyclic azaphenothiazines containing one or two quinoline rings instead of benzene rings were obtained in the original reactions of isomeric diquinodithiins, dichlorodiquinolinyl sulfides, and disulfide with aromatic amines. The type of ring fusion in the azaphenothiazine system was concluded from the ¹H NMR spectra. The obtained azaphenothiazines were evaluated in vitro for their antioxidant activity on rat hepatic microsomal membranes for protection of non-enzymatic lipid peroxidation promoted by the Fe²⁺/ascorbic acid redox system. Most compounds exhibited a very significant antioxidant activity with IC₅₀ values between 1 and 23 μM. The degree of antioxidant activity depends on the lipophilicity and molecular size as well as the (non)substitution of the thiazine nitrogen atom and type of ring system fusion. It is the first time to our knowledge that azaphenothiazines are shown to exhibit such potent antioxidant activity.

Novel benzoxazine and benzothiazine derivatives as multifunctional antihyperlipidemic agents

Atherosclerosis is a multifactorial disease with several mechanisms participating in its manifestation. To address this disorder, we applied a strategy involving the design of a single chemical compound able to simultaneously modulate more than one target. We hereby present the development of novel benzoxazine and benzothiazine derivatives that significantly inhibit in vitro microsomal lipid peroxidation and LDL oxidation as well as squalene synthase activity (IC(50) of 5-16 μM). Further, these compounds show antidyslipidemic and antioxidant properties in vivo, decreasing total cholesterol, LDL, triglyceride, and MDA levels of hyperlipidemic rats by 26-74%. Finally, by determination of their in vivo concentration (up to 24 h) in target tissues (blood/liver), it is shown that compounds reach their targets in the low micromolar range. The new compounds seem to be interesting multifunctional molecules for the development of a new pharmacophore for disease-modifying agents useful in the treatment of atherosclerosis.

Design of more potent squalene synthase inhibitors with multiple activities

With the increasing realization that modulating a multiplicity of targets can be an asset in the treatment of multifactorial disorders, we hereby report the synthesis and evaluation of the first compounds in which antioxidant, anti-inflammatory as well as squalene synthase (SQS) inhibitory activities are combined by design, in a series of simple molecules, extending their potential range of activities against the multifactorial disease of atherosclerosis. The activity of the initially synthesized antihyperlipidemic morpholine derivatives (1-6), in which we combined several pharmacophore moieties, was evaluated in vitro (antioxidant, inhibition of SQS and lipoxygenase) and in vivo (anti-dyslipidemic and anti-inflammatory effect). We further compared the in vitro SQS inhibitory action of these derivatives with theoretically derived molecular interactions by performing an in silico docking study using the X-ray crystal structure of human SQS. Based on low energy preferred binding modes, we designed potentially more potent SQS ligands. We proceeded with synthesizing and evaluating these new structures (7-12) in vitro and in vivo, to show that the new derivatives were significantly more active than formerly developed congeners, both as SQS inhibitors (20-70-fold increase in activity) and antioxidants (4-30-fold increase in activity). A significant correlation between experimental activity [Log(1/IC(50))] and the corresponding binding free energy (ΔG(b)) of the docked compounds was shown. These results, taken together, show a promising alternative and novel approach for the design and development of multifunctional antiatherosclerosis agents.

Antioxidant activity of newly synthesized 2,7-diazaphenothiazines

A series of 19 derivatives of 2,7-diazaphenothiazine was synthesized and evaluated for their antioxidant activity bearing in mind the structural similarity with "classical" phenothiazines several of which are considered powerful antioxidants. Among the new derivatives that inhibited in vitro Fe(2+)/ascorbate-induced lipid peroxidation of rat liver microsomal membranes, several exhibited significant antioxidant activity with IC(50 )values in the range of 64-125 microM. Although N-substitution led to a variable degree of antioxidant activity, the latter appears to correlate with the lipophilicity (expressed as clogP values) of the substituted derivatives. Reduced lipophilicity may also explain the relatively lower protection offered by these derivatives against lipid peroxidation when compared to their "classical" phenothiazine counterparts. Thus, modification of the phenothiazine structure by a substitution of two benzene rings with pyridine rings to form this new type of azaphenothiazines does not enhance antioxidant activity, although it retains it.

alpha1-Acid glycoprotein production in rat dorsal air pouch in response to inflammatory stimuli, dexamethasone and honey bee venom

This study shows the rapid and differential production of the 40-43 kDa and the 70-90 kDa alpha1-acid glycoprotein (AGP) fucosylated glycoforms after treatment of the dorsal air pouch with bacterial lipopolysaccharide (LPS), HgCl(2) or Freund's complete adjuvant (FCA). The 40-43 kDa and the 70-90 kDa AGP production is peaked 1-3 h post-LPS treatment. We observed that the responses to LPS and FCA are similar in that both AGP isoforms are induced whereas they differ in that the FCA exhibits a 6 h lag period. The response to HgCl(2,) however, exhibits the specific biphasic induction only of the 40-43 kDa AGP. The serum 40-43 kDa AGP glycoform gradually increases in response to all of the above stimulants and peaks by 24 h post- treatment. The increase of the 70-90 kDa AGP levels in the air pouch occurs in association with the accumulation of polymorphonuclear (PMN) cells while dexamethasone (DEX) increases only the 40-43 kDa AGP production in the absence of PMN accumulation. Macrophage-monocyte lineage cells forming the air pouch lining tissue may potentially be the cells that secrete the 40-43 kDa AGP while polymorphonuclear cells that infiltrate the air pouch secrete the 70-90 kDa AGP. The 40-43 kDa and 70-90 kDa AGP production induced by LPS in the air pouch precedes that of interleukin-1 (IL-1) or interleukin-6 (IL-6) while the 40-43 kDa AGP glycoform potentially increases IL-6 production by air pouch PMN exudate cells. These significant differences suggest a local pro-inflammatory role of AGP. Honeybee venom suppressed arthritis development and exhibited differential local or systemic regulation of AGP in serum vs. air pouch exudate or synovial fluid. This study with the air pouch model of facsimile synovium tissue suggests that local alpha1-acid glycoprotein (AGP) production may contribute to pro-inflammatory and anti-inflammatory activities during the local acute phase response or during chronic inflammatory stress as in arthritis.

Novel compounds designed as antistress agents

Agents against biologic stress were designed, containing GABA esterified with lorazepam and amidated with (R)-6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (5) or 3,5-di-tert-butyl-4-hydroxybenzoic acid (6). Compounds 5 and 6 inhibited lipid peroxidation, IC(50) 1.1 and 24 microM. Oxidative damage accompanied stress, 5 and 6 reduced radical attack, uropepsinogen, and morphological changes. Stress increased drug metabolism. Treatment with 5 reduced cytochrome P450 and N-demethylation of erythromycin, 35 and 40%. Compounds 5 and 6 decreased lipidemic indices of hyperlipidemic rats 40-63%.

EP2306 and EP2302, two novel squalene synthase inhibitors, stimulate endothelial nitric oxide synthase expression in cultured endothelial cells

EP2306 and EP2302 are two novel squalene synthase inhibitors with hypolipidemic, antiatherosclerotic, and antioxidant properties. In the present study, the authors investigated their effect on the expression and activity of endothelial nitric oxide synthase (eNOS) in cultured bovine aortic endothelial (BAE) cells and calf pulmonary artery endothelial (CPAE) cells. eNOS concentration was determined by immunoassay and eNOS activity by measuring the conversion of [(3)H]arginine to [(3)H]citrulline. Basal levels of eNOS in untreated BAE cells were 13.3 +/-1.6 ng/mg protein. Stimulation for 4 h with 30 microM of EP2306 or EP2302 resulted in increased eNOS protein level to 40% +/- 10% (p<.05) or 165% +/- 15% (p < .05) of unstimulated levels, respectively. Basal levels of eNOS in untreated CPAE cells were 3.4 +/- 0.4 ng/mg protein. Stimulation of CPAE cells for 4 h with 30 microM of EP2306 or EP2302 resulted in increased eNOS protein level to 195% +/- 24% (p < .05) and 152% +/- 19% (p < .05) of unstimulated levels, respectively. Despite their stimulatory action on eNOS expression, EP2300 compounds failed to induce any significant changes on eNOS enzymatic activity in BAE and CPAE cells. The finding that EP2300 compounds significantly increase the accumulation of eNOS in cultured endothelial cells sheds some light into their mechanism of action and supports a possible protective role of these compounds in atherosclerosis-related diseases.

Antinociceptive properties of 1,8-Cineole and beta-pinene, from the essential oil of Eucalyptus camaldulensis leaves, in rodents

1,8-cineole (cineole) and beta-pinene, two monoterpenes isolated from the essential oil obtained from Eucalyptus camaldulensis Dehn leaves were tested for antinociceptive properties. Tail-flick and hot-plate methods, reflecting the spinal and supraspinal levels, respectively, were used in mice and/or rats using morphine and naloxone for comparison. Cineole exhibited an antinociceptive activity comparable to that of morphine, in both algesic stimuli. A significant synergism between cineole and morphine was observed, but naloxone failed to antagonize the effect of cineole. Beta-pinene exerted supraspinal antinociceptive actions in rats only and it reversed the antinociceptive effect of morphine in a degree equivalent to naloxone, probably acting as a partial agonist through the mu opioid receptors. From structure-activity relationships of the pairs morphine+cineole and naloxone+beta-pinene, it was shown that similarities exist in the stereochemistry and in the respective atomic charges of these molecules. Further studies are in progress in order to elucidate the mechanism of action of the two terpenoids.

EP2306 [2-(4-Biphenyl)-4-methyl-octahydro-1,4-benzoxazin-2-ol, hydrobromide], A Novel Squalene Synthase Inhibitor, Reduces Atherosclerosis in the Cholesterol-Fed Rabbit

EP2306 [2-(4-biphenyl)-4-methyl-octahydro-1,4-benzoxazin-2-ol, hydrobromide] inhibits squalene synthase and lipid biosynthesis and possesses antioxidant properties. We hypothesized that EP2306 can effectively modify circulating lipids and reduce atherosclerosis in the cholesterol-fed rabbit. Animals were fed a high-cholesterol diet for 4 weeks followed by 4 (phase 1 and 2) or 12 weeks (phase 3) of drug treatment while on high-cholesterol diet. In phase 1, the dose-effect relationship of EP2306 on lipids and atherosclerosis was established, and its most effective dose was determined (2 mg/kg). This dose reduced significantly total cholesterol (512 +/- 96 mg/dl before versus 320 +/- 124 mg/dl after treatment, p < 0.05) and atherosclerotic lesions compared with control animals. In phase 2, the effects of 2 mg/kg EP2306, 2.5 mg/kg simvastatin, and their combination were assessed. Although no significant effect on lipid parameters was observed, there was a significant reduction (35 +/- 5%, p < 0.05) of atherosclerotic lesions in animals treated with EP2306, a similar reduction with simvastatin, and a further reduction (48 +/- 7%, p < 0.05) when the two agents were combined. In animals treated for 12 weeks with the drugs (phase 3), only EP2306 significantly reduced atherosclerotic lesions by more than 50%, whereas simvastatin alone or in combination with EP2306 had no effect. Treatment with EP2306 did not adversely affect liver transaminases or cause any histopathological changes on various organs of the animals. In conclusion, we have shown that EP2306 inhibits atherosclerosis in vivo, indicating potential as a novel therapeutic agent for coronary artery disease and other atherosclerosis-related disorders.

Effects of the novel non-steroidal anti-inflammatory compound [N-(2-thiolethyl)-2- {2- [N'- (2,6- dichlorophenyl) amino] phenyl}acetamide on cytokines and apoptosis in ischaemic rat brain

Ischaemia-reperfusion injury is associated with an inflammatory response as well as apoptosis in the affected area. Inflammatory responses are characterized, among others, by an increased production of several cytokines, while caspases are implicated in the control of apoptosis. The aim of the present work was to determine changes in the levels of inflammatory and apoptotic indices in the rat brain after cerebral ischaemia-reperfusion and to evaluate the effect of the non-steroidal anti-inflammatory compound N-(2-thiolethyl)-2-{2-[N'-[2,6-dichlorophenyl)aminolphenyl} acetamide on these indices. A cerebral ischaemia-reperfusion rodent model was used to investigate, via immunohistochemical and colorimetric techniques, the presence in the brain and spleen of inflammatory enzymes cycloxygenases COX-1 and COX-2, cytokines interleukin (IL)-1beta, IL-4, IL-6, IL-10, IL-18, tumor necrosis factor alpha (TNF-alpha) and interferon gamma (IFN-gamma) as well as the activated form of caspase-3, in treated and untreated animals. Cerebral ischaemia-reperfusion caused elevated levels in the rat post ischaemia. Treatment with the antiinflammatory derivative reduced the elevation, caused by ischaemia, of IFN-gamma, TNF-alpha, IL-1beta IL-6, IL-18 and caspase-3 levels at 3 days post ischaemia, while it increased the levels of IL-10. It was shown that the increase in concentrations of a wide range of cytokines involved in the inflammatory reaction causing brain damage after ischaemia-reperfusion can be partially reversed by the anti-inflammatory derivative used in this study.

Design and study of some novel ibuprofen derivatives with potential nootropic and neuroprotective properties

Six novel ibuprofen derivatives and related structures, incorporating a proline moiety and designed for neurodegenerative disorders, are studied. They possess anti-inflammatory properties and three of them inhibited lipoxygenase. One compound was found to inhibit cyclooxygenase (COX)-2 production in spleenocytes from arthritic rats. The HS-containing compounds are potent antioxidants and one of them protected against glutathione loss after cerebral ischemia/reperfusion. They demonstrated lipid-lowering ability and seem to acquire low gastrointestinal toxicity. Acetylcholinesterase inhibitory activity, found in two of these compounds, may be an asset to their actions.

Stress and active oxygen species--effect of alpha-tocopherol on stress response

Stress is implicated in the pathogenesis of numerous disorders such as cardiovascular diseases or neurodegeneration. The extensive overlap between diseases attributed to stress and oxidative damage is indicative of their potential relationship. We hereby study the influence of alpha-tocopherol (alpha-toc) on the development of stress biomarkers (morphological and biochemical), on specific biomarkers of radical insult (lipid peroxidation, oxidized proteins, or glutathione content in brain and liver), as well as on drug metabolism. In our experimental protocol two groups of female rats are exposed to stress conditions, i.e. cold plus starvation. Before stress and during its application one group is treated with alpha-toc for 20 d (0.42 mmol/kg per os, once daily). Our results indicate that oxidative damage accompanies the development of stress, while treatment with alpha-toc completely prevents stress-induced radical attack and reduces stress indices like plasma corticosterone, uropepsinogen, and morphological changes. It is found that stress increases the drug metabolic potential of the liver (total P450, CYP2E1, or CYP3A1 activity). Administration of alpha-toc, in combination with stress, further increases erythro mycin N-demethylation (CYP3A1) compared to stress control, while 4-nitrophenol hydroxylation (CYP2E1) is not affected significantly.

Pharmacological characterization in vitro of EP2306 and EP2302, potent inhibitors of squalene synthase and lipid biosynthesis

We investigated the effects of EP2306 and EP2302, two novel 2-biphenylmorpholine derivatives, on squalene synthase activity in rabbit and human liver microsomes, lipid biosynthesis, low-density lipoprotein (LDL) receptor expression and LDL protein uptake as well as apoB secretion in HepG2 cells. Both EP2306 and EP2302 inhibited squalene synthase activity dose-dependently. In rabbit liver microsomes, the IC50 values were 33 microM for EP2306 and 0.6 microM for EP2302 whereas in human liver microsomes, they were 63 microM for EP2306 and 1 microM for EP2302. Both EP2300 compounds inhibited cholesterol production by HepG2 cells dose dependently with IC50 values of 13.3 microM for EP2306 and 3 microM for EP2302. Furthermore, both EP2300 compounds and simvastatin significantly reduced triglyceride synthesis and apoB secretion and increased LDL receptor expression and LDL uptake in HepG2 cells. In summary, we have shown that EP2300 compounds are potent inhibitors of squalene synthase activity in rabbit and human liver microsomes and also they are effective inhibitors of cholesterol and triglyceride biosynthesis in HepG2 cells. These results suggest that EP2306 and EP2302 might prove to be useful for lipid-lowering and treatment of atherosclerosis in vivo.

Synthesis and pharmacochemical study of novel polyfunctional molecules combining anti-inflammatory, antioxidant, and hypocholesterolemic properties

We have designed and synthesized a series of novel molecules having a residue of a classical NSAID and an antioxidant moiety, both attached through amide bonds to a known nootropic structure, an L-proline, trans-4-hydroxy-L-proline or DL-pipecolinic acid residue. The compounds were found to retain anti-inflammatory and antioxidant activities, to acquire hypocholesterolemic action, and to possess a greatly reduced gastrointestinal toxicity. The novel molecules could find useful applications, among others, in slowing the progression or delaying the onset of neurodegenerative diseases.

Effect of Some Biologically Interesting Substituted Tetrahydro-1,4- Oxazines on Drug Metabolising Enzymes and on Inflammation

The effect on hepatic drug metabolising enzymes was evaluated for three representative structures and that were selected from a series of substituted oxazine derivatives designed to possess particular pharmacological properties such as analgesic, antioxidant and hypolipidemic activity. In addition, since xenobiotic metabolism, reactive oxygen and nitrogen species, atherosclerosis and inflammation are interrelated and mutually affected, the effects of and on acute inflammation in vivo and lipoxygenase activity in vitro were also investigated. It was found that treatment of rats with caused induction of cytochrome P450, enhancement of the metabolism of aminopyrine in vitro and of zoxazolamine and hexobarbital in vivo. Compound appeared to induce particularly erythromycin N-demethylation, while, a nitric ester, reduced the catalytically active cytochrome P450, although it increased the metabolism of specific cytochrome P450 substrates, i.e. 4-nitrophenol and erythromycin. Compounds and with strong hypolipidemic and antioxidant properties, reduced acute inflammatory response in two inflammation models and inhibited lipoxygenase activity in vitro. These results are helpful in optimising the biological profile as well as the potential applications of substituted oxazines.

Synthesis of chroman analogues of lipoic acid and evaluation of their activity against reperfusion arrhythmias

Novel hybrids of lipoic acid and trolox connected through triamine spacers as well as analogues in which the lipoic acid was attached at different positions of the chroman moiety of vitamin E through an amide bond, were synthesized and exhibited strong inhibition of the microsomal lipid peroxidation. Moreover, the new molecules, at 1 microM concentration, reduced reperfusion arrhythmias and MDA content on isolated rat heart preparations, with the 2- and 5-subtituted chromans possessing the better cardioprotective activity.

Synthesis and pharmacological evaluation of amide conjugates of NSAIDs with L-cysteine ethyl ester, combining potent antiinflammatory and antioxidant properties with significantly reduced gastrointestinal toxicity

The synthesis and pharmacological evaluation of a series of amide derivatives of NSAIDs with L-cysteine ethyl ester is described. The novel derivatives are potent antiinflammatory, antioxidant and hypocholesterolemic-hypolipidemic agents, while they demonstrate considerably reduced gastrointestinal toxicity. This molecular modification may offer a general route to safer antiinflammatory agents, potentially suitable for chronic use in conditions such as neurodegenerative disorders.

Synthesis and activity on free radical processes and inflammation of 9,10-dihydro-5,8-dimethoxy-triptycene-quinones

Three triptycene quinones bearing methoxy groups were prepared following a Diels-Alder methodology and were evaluated for antioxidant and anti-inflammatory activity bearing in mind their structural features that could justify intervention with free radical processes. Improved synthetic pathways were achieved for target molecules 9,10-dihydro-5,8-dimethoxy-9,10-[o]benzenoanthracene-1,4-dione (4), 9,10-dihydro-2-hydroxy-5,8-dimethoxy-9,10-[o]benzenoanthracene-1,4-dione (6), and 9,10-dihydro-2,5,8-trimethoxy-9,10-[o]benzenoanthracene-1,4-dione (9). Under our experimental conditions these compounds showed very significant antioxidant activity offering protection against lipid peroxidation of rat hepatic microsomal fraction while inhibiting the reaction completely at very low concentrations (12.5-80 microM). Moreover, compound 6 that was examined, inhibited by 44% (at 120 microM) lipoxygenase acitvity while the anti-inflammatory activity of the compounds, as assessed by the reduction of the mouse paw edema induced by Freund's complete adjuvant, was significant and comparable to that of indomethacin.

Experimental hyperlipidemia and the effect of NSAIDs

The effects of ip administration of NSAIDs in experimentally induced hyperlipidemia in rats was studied. An isotonic solution of Triton WR1339 (tyloxapol) was administered ip to rats one hour after ip administration of the examined anti-inflammatory drug. After 24 h, blood was collected for the determination of plasma total cholesterol (TC), LDL and trigluceride (TG) concentrations. The NSAIDs used in our experimental model are selective or non selective COX-1 inhibitors as well as one non selective COX-2 inhibitor. Most of the drugs significantly reduced the TC, TG and LDL concentrations in the plasma of hyperlipidemic rats. While studies link atheromatosis to inflammation, our results potentially also link anti-inflammatory activity with hypolipidemia. Thus, NSAIDs not only may address the inflammatory aspect of atherosclerosis but also may contribute directly by inducing hypolipidemia.

Effect of a novel NSAID derivative with antioxidant moiety on oxidative damage caused by liver and cerebral ischaemia-reperfusion in rats

Tissue ischaemia-reperfusion evokes toxic and harmful biochemical processes such as oxidative stress and inflammation. The aim of this study is to investigate the indices of tissue damage in rat liver and brain after ischaemia-reperfusion injury of these organs, and to study prospective cytoprotection of molecules such as the novel anti-inflammatory N-(2-thiolethyl)-2-(2-[N'-(2,6-dichlorophenyl)amino] phenyl)acetamide (compound 1) and alpha-tocopherol. Two experimental models were studied: firstly, 30 min liver ischaemia via hepatoduodenal ligament clamping followed by 60 min reperfusion; and secondly, 45 min cerebral ischaemia via bilateral common carotid artery occlusion followed by 90 min reperfusion. Compound 1 and alpha-tocopherol were administered intraperitoneally before induction of ischaemia. We hereby report that compound 1, a molecule that combines potent in-vitro antioxidant and in-vivo anti-inflammatory activity with low gastrointestinal toxicity, offered protection in-vivo against liver or brain ischaemia-reperfusion-induced damage. Both compound 1 and alpha-tocopherol prevented changes in lipid peroxidation in the rat liver and brain tissue and in tumour necrosis factor (TNF-alpha) levels in brain. Also compound 1 attenuated glutathione depletion, evoked by ischaemia-reperfusion, in the rat brain but not in the liver. These results could be explained on the basis of the antioxidant/anti-inflammatory properties of compound 1 and suggest its beneficial effect and potential therapeutic use in post-ischaemic injury.

Alkannin and shikonin: effect on free radical processes and on inflammation - a preliminary pharmacochemical investigation

Alkannin and shikonin, two natural products from Alkanna tinctoria and Lithospermum erhythrorhizon (Boraginaceae), are used in folk medicine where they are claimed to possess, among other properties, wound healing and anti-inflammatory activity. We investigated, together with the structurally related naphthazarin, their in vitro antioxidant and hydroxyl radical scavenging activity as well as their in vivo antiinflammatory activity. I was found that all examined compounds significantly inhibited in vitro lipid peroxidation of ra hepatic microsomal membranes, competed with DMSO for free hydroxyl radicals, and reduced inflammation (mouse paw edema induced by FCA) very efficiently. The examined compounds proved equal or superior to the common reference compounds for each of these properties. I is concluded that the claimed and/or proven actions of alkannin and shikonin are attributable at least partly to their intervention in free radical processes.

Antioxidant potential of natural and synthesised polyprenylated hydroquinones

The metabolites 2-octaprenyl-1,4-hydroquinone (1) and 2-(24-hydroxy)-octaprenyl-1,4-hydroquinone (2), isolated from the sponge Ircinia spinosula, along with a series of synthetic derivatives, were evaluated for their antioxidant capacity, in order to establish a potential relationship between structural characteristics and antioxidant activity. The antioxidant potential of both natural and synthesised compounds was evaluated in vitro by their ability: (1) to interact with the stable free 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) and (2) to inhibit the peroxidation, induced by the Fe(++)/ascorbate system, of heat inactivated hepatic microsomal membrane lipids. Metabolite 1 presented a strong interaction with DPPH and had a moderate effect on lipid peroxidation, while metabolite 2 interacted extensively with DPPH and exhibited a significant effect against lipid peroxidation. All derivatives retaining the free 1,4-hydroquinone system maintained fully or partly the free radical scavenging capacity.

Design, synthesis and biological evaluation of novel beta-substituted indol-3-yl ethylamido melatoninergic analogues

A series of new melatonin analogues have been synthesized. Interestingly, two of the new compounds, 11c and 11e, which did not show any appreciable affinity for the melatonin receptor, were found to be potent inhibitors of lipid peroxidation in rat liver microsomes. Analogue 11c, in particular, is a better antioxidant than melatonin.

Novel potent inhibitors of lipid peroxidation with protective effects against reperfusion arrhythmias

A series of new compounds that contain lipoic acid and trolox connected through spacers were synthesized and examined for their antioxidant activity and their protective effects against reperfusion arrhythmias in isolated heart preparations. All compounds tested are strong inhibitors of lipid peroxidation in rat liver microsomal membranes induced by ferrous ions and ascorbate. N-(3,4-Dihydro-6-hydroxy-2,5,7,8-tetramethyl-2H-1-benzopyran-2-carbonyl)-N'-(1,2-dithiolane-3-pentanoyl)-1,2-phenylenediamine (13) exhibits anti-lipid peroxidation activity at the nanomolar range. N-(3,4-Dihydro-6-hydroxy-2,5,7,8-tetramethyl-2H-1-benzopyran-2-carbonyl)-N'-(1,2-dithiolane-3-pentanoyl)ethylenediamine (10) and 13 totally suppressed reperfusion arrhythmias.

Synthesis, antiretroviral and antioxidant evaluation of a series of new benzo[b]furan derivatives

The antiretroviral and anti-oxidant profile of a series of new C-2 and C-7 substituted benzo[b]furans was explored by employing well established antiviral and antioxidant protocols. The most potent antioxidant compound tested was analog 7, which bears an OH at C-7 and a benzoyl group at C-2. In the influenza A type H3N2 virus screens analog 8a was almost five-fold more active than its counterparts and equipotent to rimantadine and amantadine. In the influenza B screening all of the new compounds tested were at least ten-fold more active than the control drug amantadine. The anti-HIV screening, using acutely infected MT-4 cells, showed that compound 8f (n = 4), was fifteen-fold more active than its monomer congeners, 8a and 8c, d and almost five-fold more potent than monomer 8b and dimer 8f (n = 3).

Reduction of gastrointestinal toxicity of NSAIDs via molecular modifications leading to antioxidant anti-inflammatory drugs

Reactive oxygen species and free radical reactions are related to several pathologic conditions including inflammation and gastric ulceration. The latter is the major undesired side-effect of almost all NSAIDs. Since this effect of NSAIDs is greatly influenced not only by the type of cyclooxygenase which is inhibited but also by the acidic nature of the molecule, we considered it interesting to modify their structure in such a way that it would lead to an antioxidant, neutral molecule or a molecule with greatly reduced acidic character. Thus, we synthesized amide derivatives of four well-known NSAIDs, i.e. diclofenac acid, tolfenamic acid, ibuprofen and indomethacin, with cysteamine, a well-known antioxidant. The synthesized derivatives, with demonstrated good anti-inflammatory and antioxidant activities, showed very significant reduction of ulcerogenicity in the investigation of gastrointestinal (GI) toxicity. As indices of ulcerogenic toxicity in rats, we used the mortality (%), the incidence of GI ulcers (%), body weight reduction (g/100 g BW) and the incidence of melena. All amide derivatives of the NSAIDs with cysteamine were almost non-toxic in the GI tract, under our experimental conditions, in contrast to their parent NSAIDs. These results are attributed to the acquired antioxidant activity as well as to the reduction of acidic character compared with the parent compounds. Therefore, it can be concluded that the combination of these two properties, anti-inflammatory and antioxidant activity, with a simultaneous drastic reduction of acidic character, may lead to the development of novel, useful anti-inflammatory and cytoprotective pharmacomolecules, with potentially important therapeutic applications.

Allosteric modulation of the adenosine A(1) receptor. Synthesis and biological evaluation of novel 2-amino-3-benzoylthiophenes as allosteric enhancers of agonist binding

Novel allosteric enhancers of agonist binding to the rat adenosine A(1) receptor are described. The lead compound for the new series was PD 81,723 ((2-amino-4, 5-dimethyl-3-thienyl)[3-(trifluoromethyl)phenyl]methanone), a compound previously reported by Bruns and co-workers (Mol. Pharmacol. 1990, 38, 950-958). The 4,5-dimethyl group and the benzoyl moiety were targets for further modifications, leading to series of 4, 5-dialkyl (12a-g), of tetrahydrobenzo (12h-u), and of tetrahydropyridine (13a-g) derivatives. A number of compounds, in particular 12b, 12e, 12j, 12n, and 12u, proved superior to PD 81,723. Their EC(50) values for enhancing the binding of the adenosine A(1) receptor agonist N(6)-cyclopentyladenosine to the receptor were lower, and/or their antagonistic activity on the adenosine A(1) receptor was shown to be diminished.

Antioxidant activity of guaiazulene and protection against paracetamol hepatotoxicity in rats

The effect of guaiazulene, a lipophilic azulene derivative widely found in nature, on radical-mediated processes is examined. The ability of guaizulene to inhibit rat hepatic microsomal membrane lipid peroxidation and to scavenge hydroxyl radicals, as well as to interact with 1,1-diphenyl-2-picrylhydrazyl radical (DPPH), was estimated. It was found that guaiazulene can inhibit lipid peroxidation very significantly, having an IC50 value of 9.8 microM. It can also scavenge hydroxyl radicals and interact with DPPH. The protection afforded by guaiazulene to rats with paracetamol-induced liver injury was also investigated. Paracetamol hepatotoxicity is caused by the reactive metabolite N-acetyl-p-benzoquinone imine (NAPQI), which causes oxidative stress and glutathione (GSH) depletion. Hepatic cytosolic protein, GSH, glutathione transferase and glutathione reductase levels are determined as indices of hepatic injury with or without the administration of guaiazulene. It was found that all parameters affected by paracetamol are restored to normal by guaiazulene treatment, while the administration of guaiazulene alone has no effect on the performed tests compared with the control values. It was concluded that the significant protection against paracetamol-induced GSH depletion and hepatic damage afforded by guaiazulene is probably connected with its antioxidant activity. A molecular mechanism of action of guaiazulene is suggested.

Effect of guaiazulene on some cytochrome P450 activities. Implication in the metabolic activation and hepatotoxicity of paracetamol

The in vitro and in vivo effect of guaiazulene, a natural azulene derivative, on rat hepatic cytochrome P450 (CYP) is investigated. Furthermore, paracetamol hepatotoxicity is induced in rats and the activity of specific cytochrome P450 forms, involved in the metabolic activation of paracetamol to the toxic metabolite N-acetyl-p-benzoquinone imine (NAPQI) is examined, after the administration of guaiazulene, using diagnostic cytochrome P450 substrates. It is found that guaiazulene inhibited considerably CYP1A2 and CYP2B1 and had a weak effect on CYP1A1 in rat hepatic microsomal fractions. Guaiazulene administered to rats did not produce any macroscopic toxic effect and caused no change of liver weight, microsomal protein and total cytochrome P450 content. Guaiazulene inhibited CYP1A2 activity in rats with or without paracetamol intoxication. Considering that CYP1A2 participates in the formation of NAPQI, as well as in the metabolic activation of several toxic and carcinogenic compounds, these results, in combination with the antioxidant activity of guaiazulene that we have found in previous investigations, indicate potential useful applications of guaiazulene.

Investigation of the effect of chamazulene on lipid peroxidation and free radical processes

Oxygen toxicity and related free radical reactions are implicated in numerous pathophysiological conditions, like atherosclerosis, inflammation, gastric ulceration, neuronal degeneration, tumour promotion. The flowers of Matricaria chamomilla, Asteraceae, have been used therapeutically for conditions in which oxidative stress is supposed to be implicated. We considered interesting to investigate the effect of Chamazulene, the active substance of chamomile, on free radical processes. Membrane lipid peroxidation was induced by Fe2+/ascorbate and assessed as the 2-thiobarbituric acid reactive material. The hydroxyl radical scavenging activity was studied as the competition of Chamazulene with DMSO for HO. generated by Fe3+/ascorbate. Finally, the interaction of Chamazulene with the N-centered stable free radical DPPH was estimated photometrically (517 nm). It was found that Chamazulene inhibited lipid peroxidation in a concentration and time dependent manner presenting an IC50 of 18 microM after 45 min incubation. It could also inhibit the autoxidation of DMSO (33 mM) by 76% at 25 mM, and had a weak capacity to interact with DPPH. In conclusion, Chamazulene presents interesting properties concerning radical processes.