Flavones. 1. Synthesis and antihypertensive activity of (3-phenylflavonoxy)propanolamines without beta-adrenoceptor antagonism.

The synthesis of a series of (3-phenylflavonoxy)propanolamines is described. These compounds were evaluated for potential antihypertensive activity in spontaneously hypertensive rats, as well as for in vivo and in vitro evidence of beta-adrenoceptor antagonism. Some of the compounds of this series exhibited effective antihypertensive properties but did not antagonize beta-adrenergic receptors. These active compounds represent a unique series of effective antihypertensive agents that, despite possessing structural characteristics typical of beta-blockers, does not have beta-adrenergic receptor blocking activity.

Flavones. 3. Synthesis, biological activities, and conformational analysis of isoflavone derivatives and related compounds.

A series of 2-alkylisoflavone derivatives 1 was prepared with the intent to study the importance of the phenyl group (at the 3-position) of the isoflavone in imparting antihypertensive activity and the substitution effects at the 2-position of isoflavone. With the exception of the 2-isopropyl analog, the antihypertensive activity of these compounds appears to have a slow onset and long duration. None of the analogs appears better than the corresponding flavone (3) and 3-phenylflavone (2) analogs. An unsuccessful attempt to correlate the relationship between antihypertensive activity and the calculated torsional angle of C2-C3-C1'-C2' is discussed. Antiinflammatory activities of these compounds along with 7-(oxypropylamine)flavones were also evaluated and found to be not very potent. The antiinflammatory activity appears to be sensitive to steric effects of the alkyl group on the nitrogen and of substituents at the 2-position of the isoflavones, while the hydroxyl group of the propanolamine side chain is not essential.

Flavones. 2. Synthesis and structure-activity relationship of flavodilol and its analogues, a novel class of antihypertensive agents with catecholamine depleting properties.

(3-Phenyl-7-flavonoxy)propanolamines have been shown to exhibit antihypertensive activity in spontaneously hypertensive rats. Although they are structurally similar to classical beta-adrenergic blocking compounds, their activity is not due to inhibition of beta-adrenoceptors. In the present study, a series of simple flavonoxypropanolamines was prepared to further explore the structural requirements for the antihypertensive effect of these compounds. A structure-activity relationship of these derivatives indicates that the position of the oxypropanolamine side chain, the hydroxy group of the side chain, steric bulkiness and length of N substituents, degree of the N-substitution, phenyl group at the 2-position of the chromone nucleus, and substituents of the phenyl group or B ring of the flavone play significant roles in imparting pharmacological effects. In addition, there is a good correlation between the antihypertensive activity and depletion of myocardial norepinephrine. Of these analogues tested, the most effective one was flavodilol. Only the 8-substituted analogue 6 was found to be a beta-antagonist. Flavodilol was chosen for in-depth pharmacological, toxicological, and clinical evaluation.

Acute heat stress model of seizures in weanling rats: influence of prototypic anti-seizure compounds.

The present study tested the therapeutic potential for prototype anti-epilepsy drugs using an animal model of infantile febrile seizures. The model consisted of immersion of weanling rats (21 days old) in a 45 degrees C water bath for a maximum of 4 min (four exposures over a 2 week period) and observing for the progression to stage-5 seizures. All compounds were administered orally at the respective ED50 for prevention of seizures in the maximal electroshock (MES) test. Clonazepam effectively lowered the score for seizure grade, shortened the duration of seizures, as well as reduced the number of animals experiencing seizures during three of the four testing periods. MK801 reduced both the maximum seizure grade, and the number of animals experiencing seizures during sessions two and three. However, the dose of MK801 caused behavioral side effects. Valproate actively decreased seizure grade, while it modestly acted to attenuate seizure duration, extended the time to seizure onset, and reduced the number of animals experiencing seizures on testing day 1. Remacemide hydrochloride and phenobarbital were not effective. The method appears useful for evaluating the potential of agents to prevent acute febrile seizures.

Flavodilol: a new antihypertensive agent.

Flavodilol, a new antihypertensive drug, was evaluated in a variety of test systems for better understanding of its biologic properties and the nature of its mechanism of action. Oral administration of the drug to spontaneously hypertensive rats (SHR) lowered arterial blood pressure (ABP) in a dose-related manner, and doses greater than 35 mg/kg increased duration but not magnitude of the response. In contrast, oral administration of flavodilol to normotensive rats did not significantly alter ABP at 35 mg/kg, although larger doses of 75 or 150 mg/kg significantly lowered ABP. In rats with DOCA/salt hypertension, flavodilol effectively lowered ABP to a degree similar to that observed in SHR. At antihypertensive doses, flavodilol did not alter blood pressure responses to a 90 degrees head-up tilt in SHR and did not influence cardiac output in conscious SHR. In addition, flavodilol did not appear to manifest its antihypertensive activity through an interaction with beta-adrenoceptors, dopamine (DA) receptors or prostaglandin synthetase. Daily oral administration of flavodilol to SHR for 4 days resulted in augmented vasopressor responses to exogenously administered epinephrine (EPI) or norepinephrine (NE) and attenuated responses to exogenously administered tyramine. In addition, flavodilol treatment attenuated in a dose-related manner ABP and heart rate (HR) responses of pithed SHR to electrical stimulation of sympathetic nerves. We conclude that flavodilol is an effective antihypertensive drug which decreases the release of NE from postganglionic sympathetic nerves, resulting in attenuation of peripheral noradrenergic function.

Neuroprotective actions of 2-amino-N-(1,2-diphenylethyl)-acetamide hydrochloride (FPL 13950) in animal models of hypoxia and global ischemia.

2-Amino-N-(1,2-diphenylethyl)-acetamide hydrochloride (FPL 13950) has been demonstrated to have good anticonvulsant efficacy and a relative lack of acute side effects in rodents. Similar in structure to remacemide hydrochloride, it was also shown to possess weak potency as an uncompetitive antagonist of N-methyl-D-aspartic acid (NMDA) receptors. In our study FPL 13950 was profiled preclinically as a potential neuroprotective agent with respect to lengthening the survival time of rodents exposed to hypoxia, as well as for ability to protect the vulnerable CA1 pyramidal neurons of the rat and dog from the consequences of global ischemia. Under conditions of hypoxia, pretreatment of rodents with FPL 13950 resulted in an extension in the time to loss of the righting reflex (rats) and mortality (rats and mice). This occurred whether the rats were maintained at ambient body temperature or made hyperthermic. When administered after 30 min of four-vessel occlusion global ischemia for periods of either 7 (b.i.d.) or 14 days (s.i.d.), FPL 13950 exhibited protection of the vulnerable CA1 hippocampal neurons in rat. In the 14-day treatment study the CA3 neurons were evaluated and FPL 13950 was found to prevent the lesser degree of ischemic-induced damage to this hippocampal region. In ischemic rats treated with FPL 13950 for 7 days, electrophysiological responses of CA1 neurons (orthodromic and antidromic population spikes, in vitro) were also preserved after FPL 13950 treatment. FPL 13950 was administered i.v. at 30 min after 8 min of clamping the ascending aorta in dogs, followed by a b.i.d./s.i.d. dosing regimen for 1 wk. Neuronal damage to CA1 was considerable in the saline-treated ischemic animals but significantly protected in dogs receiving FPL 13950. FPL 13950 continues to serve as a potential backup candidate for remacemide HCl which is currently in clinical trials for patients with stroke and epilepsy.

[S]-AR-R 15896AR-A novel anticonvulsant: acute safety, pharmacokinetic and pharmacodynamic properties.

A rational, chemical, synthetic effort to identify promising low-affinity uncompetitive N-methyl-D-aspartic acid receptor antagonists for use as antiepileptic drugs led to the discovery of AR-R 15035AR, or [RS]-alpha-phenyl-2-pyridine-ethanamine.2HCl. Chiral separation followed by intensive in vivo screening resulted in the selection of the [S] enantiomer, AR-R 15896AR, as the best compound for further preclinical development. AR-R 15896AR prevented tonic seizures in rodents for up to 6 to 8 h in response to maximal electroshock (MES), 4-aminopyridine, bicuculline, or strychnine, as well as characteristic seizures following injections of N-methyl-DL-aspartic or kainic acids. AR-R 15896AR was ineffective in two kindling models of epilepsy, did not produce tolerance to MES, and was devoid of proconvulsant and phencyclidine-like properties in mice and rats, respectively. Therapeutic indices for AR-R 15896AR were comparable to or exceeded those for standard anticonvulsants. Orally administered AR-R 15896AR rapidly entered the rat brain and was eliminated in parallel from the plasma and plasma-free compartment. A dose-response relationship between plasma and brain levels after p.o. or i.v. administration of AR-R 15896AR and protection against MES was highly correlative. The time course for loss of protection against MES mirrored the elimination of the compound from brain and plasma. The total brain concentration (25 microM) of drug at the ED50 value (approximately 3 mg/kg) for protection against MES seizures was consistent with the reported affinity of AR-R 15896AR at the N-methyl-D- aspartic acid binding site (IC50 value = 1.3 microM). The present findings demonstrated the attractiveness of AR-R 15896AR as a candidate for further development to treat epilepsy.