Amphiphilic alpha-tocopherol analogues as inhibitors of brain lipid peroxidation.

Neurological disorders, such as stroke, trauma, tardive dyskinesia, Alzheimer's and Parkinson's diseases, may be partially attributed to excessive exposition of the nervous tissue to oxygen-derived radicals. A novel water-soluble alpha-tocopherol analogue, 2,3-dihydro-2,2,4,6,7-pentamethyl-3-(4-methylpiperazino) methyl-1-benzofuran-5-ol dihydrochloride (MDL), is a potent radical scavenger. Following subcutaneous administration to mice, MDL inhibited the lipid peroxidation induced in the 100-fold diluted brain homogenates, with an ID50 of 8 mg/kg. Rapid brain penetration, within 30-60 min postadministration, and even distribution into different brain areas were observed. MDL was also detected after oral administration. In brain homogenate undergoing lipid peroxidation, MDL prevented the consumption of an equal amount of alpha-tocopherol, while inhibiting the concomitant malondialdehyde formation. The radical scavenging capacity of MDL was superior to that of alpha-tocopherol, although the peak and half-peak potentials were not significantly different. However, MDL was much less lipophilic, the partition coefficient (log P) at the octanol/water interface being 1.91. Although it is yet unknown, whether the applied criteria sufficiently predict its usefulness, beneficial effects of MDL may be expected in the above mentioned disorders.

Cardioselective ammonium, phosphonium, and sulfonium analogues of alpha-tocopherol and ascorbic acid that inhibit in vitro and ex vivo lipid peroxidation and scavenge superoxide radicals.

Analogues of alpha-tocopherol and ascorbic acid with permanently cationic substituents, i.e., phosphonium (8, 9), sulfonium (11), acylhydrazinium (13, 14), and ammonium (1, 16, 21), were synthesized, and the 2R and 2S enantiomers of the alpha-tocopherol analogues 1, 8, 11, and 13 were separated. The compounds were found to scavenge lipoperoxyl and superoxide radicals in vitro and accumulate in heart tissue (cardioselectivity) as demonstrated by measurement of ex vivo inhibition of lipid peroxidation in mouse heart homogenates and confirmed by HPLC determination of drug concentrations for 1 and 11. The 2R and 2S enantiomers of 1 inhibited ex vivo lipid peroxidation to an equal extent. Thus the in vivo uptake into myocytes (cardioselectivity) is independent of the geometry at the chiral center and common to permanently cationic compounds.

2,3-Dihydro-1-benzofuran-5-ols as analogues of alpha-tocopherol that inhibit in vitro and ex vivo lipid autoxidation and protect mice against central nervous system trauma.

A series of alpha-tocopherol analogues was synthesized with potential therapeutic value for such pathological conditions as stroke and trauma. A set of criteria such as the inhibition of in vitro lipid peroxidation, superoxyl radical scavenging, and brain penetration, as measured by ex vivo inhibition of lipid peroxidation, was applied to select the most effective compound. 2,3-Dihydro-2,2,4,6,7-pentamethyl-3-[(4-methylpiperazino)methyl]-1 - benzofuran-5-ol dihydrochloride (22) was selected because of its superior antioxidant properties and better brain penetration. This compound also protected mice against the effects of head injury. The criteria thus turned out to be useful for the characterization of a neuroprotective analogue of alpha-tocopherol.

Myocardial protection by a cardioselective free radical scavenger.

Oxygen-derived free radicals are involved in myocardial reperfusion injury. In the present study MDL 74,405 (S-(-)-3,4-dihydro-6-hydroxy-N,N,N-2,5,7,8-heptamethyl-2H-1-benzo pyran-2-ethanaminium 4-methylbenzenesulfonate), a hydrophilic derivative of alpha-tocopherol, has been shown to inhibit lipid peroxidation in rat brain homogenate, ex vivo lipid peroxidation in mouse heart and to accumulate in myocardial tissue. Infused i.v. MDL 74,405 induced a dose-related reduction of myocardial infarct size in pentobarbitone-anaesthetised rats subjected to 60 min coronary artery ligation followed by 30 min reperfusion. Similarly i.v. infusion of MDL 74,405 beginning 10 min before coronary artery occlusion (60 min) until 30 min after the onset of reperfusion (8 days) caused a decrease of infarct size associated with an increase in aortic flow. Plasma levels of creatine phosphokinase were significantly reduced. In isolated infarcted hearts, obtained from MDL 74,405-treated rats after 8 days of reperfusion and perfused according to the Langendorff technique, an increase in the contractility index (+) and (-) dP/dtmax was apparent. In isolated non-infarcted rat hearts subjected to 30 min no-flow global ischaemia, perfusion with MDL 74,405 resulted in an increase in heart rate and the contractility indices (+) dP/dtmax, and left ventricular systolic pressure during reperfusion. In conclusion MDL 74,405, is a cardioselective free radical scavenger, that reduces myocardial infarct size and attenuates post-ischaemic dysfunction.

Protection of infarcted, chronically reperfused hearts by an alpha-tocopherol analogue.

Free radicals may cause part of the irreversible injury which occurs during myocardial infarction and reperfusion. In the present study MDL 73404, a hydrophilic, cardioselective, free radical scavenger analogue of alpha-tocopherol, was evaluated for its effects on infarct size as well as on indicators of reperfusion injury. A pentobarbitone-anaesthetised rat model of coronary artery ligation (60 min; followed by 8 days of reperfusion) was used. Intravenous infusion of MDL 73404 (3 mg/kg per h) began 10 min before occlusion until 30 min after the onset of reperfusion. MDL 73404 reduced (P < 0.02) the elevated serum levels of thiobarbituric acid reactive substances and plasma levels of creatine phosphokinase (P < 0.01). An increase in cardiac output and heart rate together with a decrease (P < 0.01) in infarct size was evident in rats that had received MDL 73404, 8 days previously. Isolated infarcted hearts obtained from rats after 8 days of reperfusion had greater (P < 0.01) + dP/dt max, -dP/dt max, left ventricular systolic pressure and coronary flow after MDL 73404 compared to saline-treated controls. Infusion of [14C]MDL 73404, during the time of occlusion resulted in a concentration of 14.5 +/- 2.2 mg eq/g in the non-ischaemic ventricular tissue and a concentration of 3.0 +/- 0.4 mg eq/g in the area at risk. After infusion for the 30 min of reperfusion, 6.4 +/- 0.2 mg eq/g was detected in the non-ischaemic ventricular tissue but only 3.1 +/- 0.5 mg eq/g in the area at risk.(ABSTRACT TRUNCATED AT 250 WORDS)

Protective effects of an alpha-tocopherol analogue against myocardial reperfusion injury in rats.

Free radicals may cause part of the irreversible injury which occurs during myocardial infarction and reperfusion. In the present study MDL 73404, an alpha-tocopherol analogue which is a free radical scavenger has been evaluated for its effects on infarct size in an anaesthetised rat model of coronary artery ligation (60 min) and reperfusion (30 min). Intravenous infusion of the compound began 10 min before occlusion until the end of reperfusion. MDL 73404 (0.3-3 mg/kg per h) reduced infarct size, although not in a dose-related manner. Infusion of MDL 73404 (3 mg/kg per h) commencing 30 min before reperfusion until the end of reperfusion also induced a significant reduction in infarct size. In the isolated rat heart (Langendorff technique) subjected to 30 min no-flow global ischaemia, pretreatment with MDL 73404 (0.03 and 0.1 mM) in the perfusion buffer and during 30 min of reperfusion resulted in a significant increase in the maximal pressure development (+dP/dt max) and relaxation (-dP/dt max), left ventricular systolic pressure and heart rate during reperfusion, whereas left ventricular diastolic pressure was significantly reduced. In contrast, only one control heart out of five exhibited signs of recovery. Replacement, for 2 min, with a cardioplegic solution before the 30 min period of ischemia resulted in an increased heart rate and contractility during reperfusion compared to hearts that did not receive the cardioplegic solution. The presence of MDL 73404 (0.03 and 0.1 mM) in the perfusion fluid induced an additional increase in left ventricular systolic pressure to the pre-ischaemic levels. MDL 73404 may have potential for cardioprotective use in acute reperfusion of the myocardium following ischaemia.

Cardioselectivity of alpha-tocopherol analogues, with free radical scavenger activity, in the rat.

MDL74270 (6-acetyloxy-3,4-dihydro-N,N,N,2,5,7, 8-heptamethyl-2H-1-benzopyran-2-ethanaminium, 4-methylbenzenesulfonate) is a quaternary amine analogue of alpha-tocopherol with free radical scavenger properties. Rats were injected iv with [14C]MDL74270 (0.91 mg/kg), and whole blood and heart tissue were sampled. Five min after drug, the heart tissue/blood ratio (T/B) of radioactivity was 3.5, whereas at 1 hr it was 20.1 and remained at this value up to at least 6 hr. After iv administration the t 1/2 of radioactivity in blood was 6.3 hr, but po blood levels could not be quantified. The 0- to 96-hr urinary elimination of radioactivity was 39.9 +/- 5.7% of the dose after iv and only 1.2 +/- 0.4% after po administration, conversely, 44.7 +/- 5.2% was excreted in feces after iv and 79.1 +/- 17.4% after po administration. These results confirmed poor oral absorption of the compound. Tissue distribution of [14C]MDL74270 was compared with that of its tertiary amine analogue [14C]MDL74366 in rat heart, skeletal muscle, brain, and whole blood, after iv administration (1 mg/kg). The heart T/B was above 20, 1-6 hr after [14C]MDL74270, whereas it was less than 2 after [14C]MDL74366. Over the 1- to 6-hr time interval, skeletal muscle T/B varied from 1.8 to 5 compared with 1.5 to 0.6 for [14C] MDL74366. Brain T/B was higher after the tertiary amine compound. Results showed marked cardioselectivity of radioactivity after [14C] MDL74270. Differential centrifugation of heart homogenates showed that radioactivity was equally distributed between the major subcellular fractions studied.(ABSTRACT TRUNCATED AT 250 WORDS)

A cardioselective, hydrophilic N,N,N-trimethylethanaminium alpha-tocopherol analogue that reduces myocardial infarct size.

The alpha-tocopherol analogue 3,4-dihydro-6-hydroxy-N,N,N,2,5,7,8- heptamethyl-2H-1-benzopyran-2-ethanaminium 4-methylbenzenesulfonate (1a, MDL 73404) and its O-acetate 1b (MDL 74270) were synthesized. Compound 1a was found to be hydrophilic (log P = -0.60) and to prevent lipid autoxidation in rat brain homogenate with an IC50 of 1.7 +/- 0.9 microM. Tissue distribution studies with [14C]-1b in rats (1 mg/kg iv) showed that radioactivity accumulates in the heart (ratio 20:1 vs blood after 1 h). Infusion of 1 mg/kg per h of 1b bromide reduced infarct size by 54% in rats subjected to coronary artery occlusion for 60 min followed by reperfusion for 30 min, compared to saline-infused controls. By comparison, the tertiary amine analogue 5 was found not to accumulate in heart tissue, to be an equally effective free-radical scavenger in vitro, but to require a higher dose to reduce infarct size in rats. This shows that the cardioselectivity of compound 1 contributes to its potency in salvaging myocardial tissue in rats after ischemia and reperfusion.

Effect of a cardioselective alpha-tocopherol analogue on reperfusion injury in rats induced by myocardial ischaemia.

Free radicals may cause some of the irreversible injury which occurs during myocardial ischaemia and reperfusion. In the present study the effects of a cardioselective, free radical scavenger, MDL 74270, which is an analogue of alpha-tocopherol, on myocardial infarct size in an anaesthetised rat model of coronary artery ligation (60 min) and reperfusion (30 min) has been evaluated. Infusion of MDL 74270 (0.3-3.0 mg/kg per h) commencing 10 min before occlusion until the end of reperfusion significantly reduced infarct size. The highest dose also caused a significant reduction in serum creatine phosphokinase levels. Similar findings have been obtained with the bromide salt of MDL 74270. Tissue distribution studies with 14C-labelled MDL 74270 and its tertiary amine analogue (MDL 74366) showed heart/blood ratios of total radioactivity, 1-6 h after i.v. administration, greater than 20 after MDL 74270 and around 1 after MDL 74366. The importance of accumulation of total radioactivity in the heart after MDL 74270 is supported by the fact that MDL 74366 was 30 times less potent as a myocardial protector in the ligation/reperfusion studies. It is concluded that MDL 74270 has potential for cardioprotective use in conditions of acute reperfusion.

A water-soluble quaternary ammonium analog of alpha-tocopherol, that scavenges lipoperoxyl, superoxyl and hydroxyl radicals.

The new water-soluble ammonium-analog of alpha-tocopherol (vitamin E) (compound 1: 3,4-dihydro-6-hydroxy-N,N, N-2,5,7,8-heptamethyl-2H-1-benzopyran-2-ethanaminium 4-methylbenzenesulfonate) and its tertiary amine derivative (compound 2: 3,4-dihydro-2-(2-dimethylaminoethyl)-2,5,7,8-tetramethyl-2H-1-benzopyran -6-ol hydrochloride) were investigated as scavengers of oxygen-derived free radicals. Compounds 1 and 2 were at least 40 times more potent inhibitors of Fe-driven heart microsomal lipid peroxidation than Trolox. While the alpha-tocopherol analogs had the same potency as scavengers of xanthine/xanthine oxidase-generated superoxyl radicals, the thiol compounds D,L-penicillamine and N-2-mercaptopropionyl glycine reacted at a much slower rate. The O-acetyl derivatives of compounds 1 and 2 were not scavengers of superoxyl radicals. Considerable differences between the alpha-tocopherol analogs were observed in their competition with 2-deoxyribose for hydroxyl radicals (OH.). Compound 2 was equipotent with Trolox and thiourea, whereas the reactivity of these substances was diminished by more than 30% as compared to compound 1. Although showing lower reactivity, the O-acetyl derivatives of compounds 1 and 2 were active nevertheless as OH.-scavengers. The previously reported high potency of compound 1 in reducing infarct size during myocardial ischemia/reperfusion appears to be due to its radical-scavenging properties, likely to be enhanced by its previously described cardioselectivity.

Pharmacology of enoximone.

Enoximone is a new cardiotonic agent, active by both intravenous and oral routes of administration, that is being studied clinically for the treatment of patients with congestive heart failure. The animal pharmacology pertinent to the clinical development of enoximone is reviewed. Direct positive inotropic, positive chronotropic and vasodilator properties have been demonstrated for enoximone in several in vivo and in vitro preparations. However, positive inotropism and vasodilation are the principal effects of this agent with the inotropic effect being the most prominent. In anesthetized dogs, the cardiovascular effects produced by enoximone (0.1 to 1 mg/kg) were not accompanied by significant alterations in myocardial oxygen consumption. Cardiac function was improved by enoximone in anesthetized dogs given myocardial depressant amounts of propranolol. Studies in vivo and in vitro have indicated that the actions of enoximone are direct and not mediated by stimulation of adrenergic receptors, histaminic receptors, cholinergic receptors, Ca++-adenosine triphosphatase, Mg++-adenosine triphosphatase, adenyl cyclase or inhibition of Na+, K+-adenosine triphosphatase. However, enoximone reversed the depressant effects of verapamil in the dog heart-lung preparation; this suggests that its action resulted in the activation of slow calcium channels. Enoximone was found to be potent and highly selective inhibitor of a high affinity cyclic adenosine monophosphate-phosphodiesterase type IV-phosphodiesterase from dog heart, whereas standard inhibitors (e.g., 3-isobutyl-1-methylxanthine and papaverine) inhibit all 3 cardiac phosphodiesterases. Further, enoximone produced an increase in cyclic adenosine monophosphate, but not cyclic guanosine monophosphate, in the isolated, blood perfused dog papillary muscle during the peak inotropic effect.(ABSTRACT TRUNCATED AT 250 WORDS)

4-Aroyl-1,3-dihydro-2H-imidazol-2-ones, a new class of cardiotonic agents.

A series of 4-aroyl-1,3-dihydro-2H-imidazol-2-ones was synthesized and evaluated for pharmacological activity in the anesthetized dog. Most members of this series produced dose-related increases in cardiac contractile force as well as relatively minor increases in heart rate and decreases in systemic arterial blood pressure that were not blocked by propranolol. In general, 4-methoxy or 4-methylthiobenzoyl substitution afforded compounds of greatest inotropic potency. 1,3-Dihydro-4-(4-methoxybenzoyl)-5-methyl-2H-imidazol-one (6) was shown to produce a dose-related positive inotropic effect and reverse the depressant effect of pentobarbital on cardiac pump function in the dog heart-lung preparation. The cardiotonic activity of this series may have important utility in the treatment of congestive heart failure. 1,3-Dihydro-4-[4-(methylthio)benzoyl]-5-methyl-2H-imidazol-2-one (17) was chosen for human studies and is currently undergoing clinical trials.

Salicylamide derivatives related to medroxalol with alpha- and beta-adrenergic antagonist and antihypertension activity.

Analogues of medroxalol (1) were prepared in which the carboxamide function, the phenolic hydroxy group, and the aralkylamine side chain were modified. N-alkyl-substituted amide analogues of 1 showed diminishing beta-blocking activity with increasing steric bulk of the alkyl group. This allowed the conclusion that deactivation of the phenolic hydroxy group of 1 by the carbonyl group of the amide function is responsible for the beta-adrenergic antagonistic properties of 1. This conclusion was strengthened by the finding that the phenolic O-methyl analogue 5-[2-[[3-(1,3-benzodioxol-5-yl)-1-methylpropyl]amino]-1hydroxyethyl]-2-methoxybenzamide (13) was found to have enhanced beta-adrenergic blocking activity. The finding that 13 also had decreased alpha-blocking activity compared to 1 indicated that the phenolic hydroxy group of 1 enhances alpha-adrenergic antagonism. The finding that 1 and 13 showed such a large difference in relative alpha- to beta-blocking potency while exhibiting approximately equal antihypertensive activity in spontaneously hypertensive rats was surprising. In indicated that pharmacologic properties other than alpha- and beta-adrenergic blockade may contribute to the antihypertensive activity of medroxalol. One of the analogues in which the aralkylamine side chain of 1 was replaced by a fragment of a known alpha-adrenergic receptor blocker, 2-hydroxy-5-[1-hydroxy-2-[4-(2-methylphenyl)-1-piperazinyl]ethyl]benzamide (22), showed an interesting pharmacologic profile of potential therapeutic usefulness.

5-(Tetradecyloxy)-2-furancarboxylic acid and related hypolipidemic fatty acid-like alkyloxyarylcarboxylic acids.

5-(Tetradecyloxy)-2-furancarboxylic acid (91, RMI 14514) was found to lower blood lipids and to inhibit fatty acid synthesis with minimal effects on liver weight and liver fat content. This fatty acid-like compound represents a new class of hypolipidemic agent; it is effective in rats and monkeys. The compound resulted from discovery of hypolipidemic activity in certain beta-keto esters, postulation and confirmation of the corresponding benzoic acids as active metabolites, and systematic exploration of the structure--activity relationships.

(2-Piperidine)- and (2-pyrrolidine)ethanones and -ethanols as inhibitors of blood platelet aggregation.

(E)-4-[4-(Methylthio)phenyl]-1-(2-piperidinyl)-3-buten-2-one hydrochloride (44, RMI 14 133A) was found to inhibit ADP-induced aggregation of blood platelets. It was selected from a large series of (2-piperidinyl)- and (2-pyrrolidinyl)ethanones synthesized by a modified Schopf reaction from enolate magnesium salts of beta-keto acids and 2,3,4,5-tetrahydropyridine trimer or 3,4-dihydro-2H-pyrrole trimer, respectively. Evaluation of the compounds was carried out in vitro on human blood platelets. Structure-activity relationships are discussed. 44 also inhibited platelet aggregation ex vivo in guinea pigs. Subacute toxicity evaluation in dogs and guinea pigs showed it to have an unfavorable therapeutic ratio. 1-[4'-Chloro(1,1'-biphenyl)-4-yl-a1-2-(2-piperdinyl)ethanone hydrochloride (18, RMI 12436A) was found to lower serum cholesterol levles in rats with concurrent accumulation of (3beta)-cholesta-5,7-dien-3-ol, suggesting inhibition of 7-dehydrocholesterol delta7-reductase.

Bis-basic-substituted polycyclic aromatic compounds. A new class of antiviral agents. 7. Bisalkamine esters of 9-oxoxanthene-2,7-dicarboxylic acid, 3,6-bis-basic ethers of xanthen-9-one, and 2,7-bis(aminoacyl)xanthen-9-ones-xanthenes, and -thioxanthenes.

3,6-Bis[2-(dimethylamino)ethoxy]-9H-xanthen-9-one dihydrochloride (4, RMI 10874DA) and 1,1'-(9H-xanthene 2,7-diyl)bis[2-(dimethylamino)ethanone] dihydrochloride (16, RMI 11513DA) were found to prolong survival of mice infected with lethal challenges of encephalomyocarditis (EMC) virus. They were effective by oral as well as subcutaneous administration and showed broad-spectrum antiviral activity. They were selected for preclinical evaluation from the five series of compounds named in the title that were synthesized in analogy to tilorone and related fluorenone derivatives, described earlier. In addition to 4 and 16, compounds 11, 12, 17, and 18 showed high antiviral activity on oral as well as subcutaneous administration. High antiviral activity on subcutaneous admistration was found in the bisalkamine esters 1,2, and 14, the bis(aminoacyl)xanthenes 23 and 26, the bis(aminoalkylene)xanthene 31, the bis(aminoacyl)thioxanthenes 34-40, and the bis-basic ethers of 9-benzylide-nexanthenes 41 and 42. Structure-activity relationships showed a decrease of oral activity with increased length of side chains and increased molecular weight of dialkylamino substituents of 3,6-bis-basic ethers of xanthen-9-one and of 2,7-bis(aminoacyl)xanthenes and-xanthen-9-ones. At least one carbonyl or alkenyl function in conjugation to the xanthene nucleus either at the 9 position of the nucleus or in the side chains is required for high antiviral activity.

Substituted alpah-methylbenzyl and tricyclic arylalkyl lactamimides as inhibitors of blood platelet aggregation.

N-[1-(p-Phenoxyphenyl)ethyl]hexahydro-2H-azepin-2-imine hydrochloride (10) and N-[1-(2-dibenzothienyl)-ethyl]hexahydro-2H-azepin-2-imine hydrochloride (22) were found to inhibit in vitro aggregation of human blood platelets induced by ADP with minimal release of procoagulant platelet factor 3. The compounds were selected from a series of substituted alpha-methylbenzyl and tricyclic arylalkyl lactamimides that were free of hypoglycemic and diuretic effects. Compounds 10 and 22, as well as N-[1-(1-naphthyl)ethyl]hexahydro-2H-azepin-2-imine hydrochloride (I) and N-(2,2-diphenylpentyl)hexahydro-2H-azepin-2-imine hydrochloride (II), were evaluated for effects on ADP-induced platelet aggregation after repeated oral administration to guinea pigs. Compound II (RMI 12,366A) showed in vivo activity in this system 2 h after the last of four daily doses of 100 mg/kg po.

Hypoglycemic alpha-cycloalkylphenylmehtyl, furanalkyl, and thiophenealkyl lactamimides.

A series of alpha-cycloalkylphenylmethyl lactamimides and a series of furan- and thiophenealkyl lactamimides were prepared for biological evaluation as an extension of earlier finding of hypoglycemic activity in lactamimides. Compounds 7, 20, 23, 25, 29, and 32 produced pronounced hypoglycemia after oral administration to fasted, glucose-primed rats.