Anna Rapacz

Preliminary evaluation of pharmacological properties of some xanthone derivatives

A series of xanthone derivatives were synthesized and examined for electrocardiographic, antiarrhythmic, hypotensive and anticonvulsant activities as well as for alpha(1)- and beta(1)-adrenergic binding affinities. Among the investigated compounds, some of them exhibited significant antiarrhythmic and/or hypotensive activity. The data obtained via receptor binding assay are in agreement with pharmacological results and could explain antiarrhythmic and/or hypotensive activity of the newly synthesized structures.

Synthesis and Evaluation of Antidepressant‐like Activity of Some 4‐Substituted 1‐(2‐methoxyphenyl)Piperazine Derivatives

A series of new derivatives of N‐(2‐methoxyphenyl)piperazine have been synthesized for their affinity toward serotonergic receptors and for their potential antidepressant‐like activity. They have been evaluated toward receptors 5‐HT1A, 5‐HT6, and 5‐HT7, as well as in vivo in the tail suspension, locomotor activity, and motor co‐ordination tests. All the tested compounds proved very good affinities toward 5‐HT1A and 5‐HT7 receptors. The most promising compound was 1‐[(2‐chloro‐6‐methylphenoxy)ethoxyethyl]‐4‐(2‐methoxyphenyl)piperazine hydrochloride, exhibiting affinity toward receptors Ki <1 nm (5‐HT1A) and Ki = 34 nm (5‐HT7). Antidepressant‐like activity (tail suspension test) was observed at 2.5 mg/kg b.w. (mice, i.p.), and the effect was stronger than that observed for imipramine (5 mg/kg b.w.). Sedative activity was observed at ED50 (locomotor test, mice, i.p.) = 17.5 mg/kg b.w. and neurotoxicity was observed at TD50 (rotarod, mice, i.p.) = 53.2 mg/kg b.w.

Design, synthesis and biological evaluation of new hybrid anticonvulsants derived from N-benzyl-2-(2,5-dioxopyrrolidin-1-yl)propanamide and 2-(2,5-dioxopyrrolidin-1-yl)butanamide derivatives

The purpose of this study was to synthesize the library of 33 new N-benzyl-2-(2,5-dioxopyrrolidin-1-yl)propanamides, 2-(3-methyl-2,5-dioxopyrrolidin-1-yl)propanamides, and 2-(2,5-dioxopyrrolidin-1-yl)butanamides as potential new hybrid anticonvulsant agents. These hybrid molecules join the chemical fragments of well-known antiepileptic drugs (AEDs) such as ethosuximide, levetiracetam, and lacosamide. The coupling reaction of the 2-(2,5-dioxopyrrolidin-1-yl)propanoic acid, 2-(3-methyl-2,5-dioxopyrrolidin-1-yl)propanoic acid, or 2-(2,5-dioxopyrrolidin-1-yl)butanoic acid with the appropriately substituted benzylamines in the presence of the coupling reagent, N,N-carbonyldiimidazole (CDI) generated the final compounds 4-36. Spectral data acquired via (1)H NMR, (13)C NMR, and LC-MS confirmed the chemical structures of the newly prepared compounds. The initial anticonvulsant screening was performed in mice intraperitoneally (ip), using the maximal electroshock seizure (MES) and subcutaneous pentylenetetrazole (scPTZ) seizure tests. The rotarod test determined the acute neurological toxicity (NT). The results of preliminary pharmacological screening revealed that 25 compounds showed protection in half or more of the animals tested in the MES and/or scPTZ seizure models at the fixed dose of 100mg/kg. The broad spectra of activity across the preclinical seizure models displayed compounds 4, 7, 8, 13, 15-18, 24, and 26. The quantitative pharmacological studies in mice demonstrated the highest protection for compounds 4 (ED50 MES=67.65 mg/kg, ED50scPTZ=42.83 mg/kg); 8 (ED50 MES=54.90 mg/kg, ED50scPTZ=50.29 mg/kg); and 20 (ED50scPTZ=47.39 mg/kg). These compounds were distinctly more potent and provided better safety profiles in the rotarod test compared to valproic acid or ethosuximide, which were used as model AEDs. Compound 8 underwent only a slight metabolic change by the human liver microsomes (HLMs), and also did not affect the activity of human cytochrome P450 isoform, CYP3A4, in the in vitro assays.

Design, synthesis, and anticonvulsant activity of new hybrid compounds derived from 2-(2,5-dioxopyrrolidin-1-yl)propanamides and 2-(2,5-dioxopyrrolidin-1-yl)butanamides.

The library of 27 new 1-(4-phenylpiperazin-1-yl)- or 1-(morpholin-4-yl)-(2,5-dioxopyrrolidin-1-yl)propanamides and (2,5-dioxopyrrolidin-1-yl)butanamides as potential new hybrid anticonvulsant agents was synthesized. These hybrid molecules join the chemical fragments of well-known antiepileptic drugs (AEDs) such as ethosuximide, levetiracetam, and lacosamide. Compounds 5, 10, 11, and 24 displayed the broad spectra of activity across the preclinical seizure models, namely, the maximal electroshock (MES) test, the subcutaneous pentylenetetrazole (scPTZ) test, and the six-hertz (6 Hz) model of pharmacoresistant limbic seizures. The highest protection was demonstrated by 11 (ED50 MES = 88.4 mg/kg, ED50 scPTZ = 59.9 mg/kg, ED50 6 Hz = 21.0 mg/kg). This molecule did not impair the motor coordination of animals in the chimney test even at high doses (TD50 > 1500 mg/kg), yielding superb protective indexes (PI MES > 16.97, PI PTZ > 25.04, PI 6 Hz > 71.43). As a result, 11 displayed distinctly better safety profile than clinically relevant AEDs ethosuximide, lacosamide, or valproic acid.

Antidepressant- and Anxiolytic-Like Effects of New Dual 5-HT1A and 5-HT7 Antagonists in Animal Models

The aim of this study was to further characterize pharmacological properties of two phenylpiperazine derivatives: 1-{2-[2-(2,6-dimethlphenoxy)ethoxy]ethyl}-4-(2-methoxyphenyl)piperazynine hydrochloride (HBK-14) and 2-[2-(2-chloro-6-methylphenoxy)ethoxy]ethyl-4-(2- methoxyphenyl)piperazynine dihydrochloride (HBK-15) in radioligand binding and functional in vitro assays as well as in vivo models. Antidepressant-like properties were investigated in the forced swim test (FST) in mice and rats. Anxiolytic-like activity was evaluated in the four-plate test in mice and elevated plus maze test (EPM) in rats. Imipramine and escitalopram were used as reference drugs in the FST, and diazepam was used as a standard anxiolytic drug in animal models of anxiety. Our results indicate that HBK-14 and HBK-15 possess high or moderate affinity for serotonergic 5-HT2, adrenergic α1, and dopaminergic D2 receptors as well as being full 5-HT1A and 5-HT7 receptor antagonists. We also present their potent antidepressant-like activity (HBK-14—FST mice: 2.5 and 5 mg/kg; FST rats: 5 mg/kg) and (HBK-15—FST mice: 1.25, 2.5 and 5 mg/kg; FST rats: 1.25 and 2.5 mg/kg). We show that HBK-14 (four-plate test: 2.5 and 5 mg/kg; EPM: 2.5 mg/kg) and HBK-15 (four-plate test: 2.5 and 5 mg/kg; EPM: 5 mg/kg) possess anxiolytic-like properties. Among the two, HBK-15 has stronger antidepressant-like properties, and HBK-14 displays greater anxiolytic-like activity. Lastly, we demonstrate the involvement of serotonergic system, particularly 5-HT1A receptor, in the antidepressant- and anxiolytic-like actions of investigated compounds.

Design, synthesis and biological activity of new amides derived from 3-methyl-3-phenyl-2,5-dioxo-pyrrolidin-1-yl-acetic acid.

A series of new 3-methyl-3-phenyl-2,5-dioxo-pyrrolidin-1-yl-acetamides (6-23) has been synthesized and evaluated for their anticonvulsant activity in the maximal electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ) seizure tests after intraperitoneal injection in mice. The acute neurological toxicity was determined using the rotarod test. The in vivo preliminary pharmacological results showed that in the whole series only two compounds (15, 21) were devoid of activity, whereas other molecules revealed protection in at least one animal model of epilepsy (MES or/and scPTZ). The in vivo quantitative studies in mice showed that in the MES test the most active were 1-{2-[4-(2-methoxyphenyl)-piperazin-1-yl]-2-oxo-ethyl}-3-methyl-3-phenyl-pyrrolidine-2,5-dione (17), 1-{2-[4-(4-fluorophenyl)-piperazin-1-yl]-2-oxo-ethyl}-3-methyl-3-phenyl-pyrrolidine-2,5-dione (8), and its 2-fluorophenyl analog (7) with ED50 values of 97.51 mg/kg (17), 104.11 mg/kg (8), and 114.68 mg/kg (7), respectively. In the scPTZ screen the most potent were compound 6 with an ED50 = 40.87 mg/kg, and 4-benzylpiperidine derivative 22 - ED50 = 60.00 mg/kg. Furthermore, selected compounds 8, 14, 17, and 23 were tested in the psychomotor seizure 6-Hz test. Compounds 7, 8, and 17 revealed significant analgesic activity in the formalin model of tonic pain in mice, without impairment of the motor coordination in the chimney test. The in vitro binding studies showed that the mechanism of anticonvulsant activity may be partially related with the influence on the voltage-gated sodium and calcium channels. The mutagenic and antimutagenic effects of 13, 17, and 22 were evaluated using the novel Vibrio harveyi assay.

Antidepressant-like activity of a new piperazine derivative of xanthone in the forced swim test in mice: The involvement of serotonergic system

BACKGROUND The studied compound: 3-chloro-5-{[4-(2-hydroxyethyl)piperazin-1-yl]methyl}-9H-xanthen-9-one dihydrochloride (HBK-6) is a new xanthone derivative. In this study we investigated its antidepressant-like properties and possible mechanism of action. METHODS Antidepressant-like activity was evaluated in the forced swim test (FST) in mice. The influence on locomotor activity in mice was analyzed to determine whether the observed in FST effect is specific. Rotarod test was used to determine neurotoxic properties. RESULTS HBK-6 reduced immobility time in mice in FST at the doses 5 and 10mg/kg, whereas fluoxetine (FX) at 15 mg/kg, reboxetine (RX) at 10mg/kg and bupropion (BPR) at 5mg/kg. Joint administration of sub-effective doses of HBK-6 and FX, but not RX or BPR, reduced immobility in mice in FST. HBK-6 at the dose 5mg/kg did not show activity in FST after pretreatment with p-chlorophenylalanine. The studied xanthone derivative at the doses 5 and 10mg/kg did not impair motor coordination in mice. CONCLUSIONS We demonstrated that HBK-6 has a potent antidepressant-like activity in FST, stronger than that of FX and RX, and seems to mediate its effect through serotonergic system. Moreover, at antidepressant-like doses it does not show neurotoxic properties. Given the promising results, HBK-6 may have potential in the treatment of depression, but this needs extended studies.

Evaluation of anticonvulsant and antinociceptive properties of new N-Mannich bases derived from pyrrolidine-2,5-dione and 3-methylpyrrolidine-2,5-dione

The aim of the present experiments was to examine anticonvulsant activity of new pyrrolidine-2,5-dione and 3-methylpyrrolidine-2,5-dione derivatives in animal models of epilepsy. In addition, the possible collateral antinociceptive activity was assessed. Anticonvulsant activity was investigated in the electroconvulsive threshold (MEST) test and the pilocarpine-induced seizure models in mice. Antinociceptive activity was examined in the hot plate and the formalin tests in mice. Considering the drug safety evaluation, the Vibrio harveyi test was used to estimate anti/mutagenic activity. To determine the plausible mechanism of anticonvulsant action, for two chosen compounds (12 and 23), in vitro binding assays were carried out. All of the tested compounds revealed significant anticonvulsant activity in the MEST test. Compounds 12 and 23 displayed anticonvulsant effect also in pilocarpine-induced seizures. Four of the tested compounds (12, 13, 15, and 24) revealed analgesic activity in the hot plate test as well as in the first phase of the formalin test, and all of them were active in the second phase of the formalin test. The possible mechanism of action of compounds 12 and 23 is the influence on the neuronal voltage-sensitive sodium and L-type calcium channels. The obtained results indicate that in the group of pyrrolidine-2,5-diones, new anticonvulsants with collateral analgesic properties can be found.

The antidepressant-like activity of 6-methoxy-2-[4-(2-methoxyphenyl)piperazin-1-yl]-9H-xanthen-9-one involves serotonergic 5-HT1A and 5-HT2A/C receptors activation

Xanthone derivatives have been shown to posses many biological properties. Some of them act within the central nervous system and show neuroprotective or antidepressant-like properties. Taking this into account we investigated antidepressant-like activity in mice and the possible mechanism of action of 6-methoxy-2-[4-(2-methoxyphenyl)piperazin-1-yl]-9H-xanthen-9-one (HBK-11) - a new xanthone derivative. We demonstrated that HBK-11 produced antidepressant-like effects in the forced swim test and tail suspension test, comparable to that of venlafaxine. The combined treatment with sub-effective doses of HBK-11 and fluoxetine (but not reboxetine or bupropion) significantly reduced the immobility in the forced swim test. Moreover, the antidepressant-like activity of HBK-11 in the aforementioned test was blocked by p-chlorophenylalanine, and significantly reduced by serotonergic 5HT1A receptor antagonist - WAY-1006335 and 5HT2A/C receptor antagonist - ritanserin. As none of the above treatments influenced the spontaneous locomotor activity, it can be concluded that HBK-11 mediates its activity through a serotonergic system, and its antidepressant-like effect involves 5HT1A and 5HT2A/C receptor activation. Furthermore, at antidepressant-like doses HBK-11 did not cause the mice to display locomotor deficits in rotarod or chimney tests. Considering the pharmacokinetic profile, HBK-11 demonstrated rapid absorption after i.p. administration, high clearance value, short terminal half-life, very high volume of distribution and incomplete bioavailability. The compound studied had good penetration into the brain tissue of mice. Since studied xanthone derivative seems to present interesting, untypical mechanism of antidepressant-like action i.e. 5HT2A/C receptor activation, it may have a potential in the treatment of depressive disorders, and surely requires further studies.

Synthesis, Physicochemical, and Anticonvulsant Properties of New N-Mannich Bases Derived from Pyrrolidine-2,5-dione and Its 3-Methyl Analog

A series of 22 new N‐[(4‐phenylpiperazin‐1‐yl)‐methyl]‐3‐methyl‐pyrrolidine‐2,5‐dione and pyrrolidine‐2,5‐dione derivatives were synthesized and evaluated for their anticonvulsant activities in the maximum electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ) seizure tests after intraperitoneal injection into mice. The neurotoxicity was determined applying the rotarod test. The in vivo results in mice showed that seven compounds were effective in the MES or/and scPTZ seizure tests. The quantitative evaluation in both tests after i.p. administration into mice revealed that the most active compounds were N‐[{4‐(3,4‐dichlorophenyl)‐piperazin‐1‐yl}‐methyl]‐3‐methylpyrrolidine‐2,5‐dione (12) with ED50 = 16.13 mg/kg (MES), ED50 = 133.99 mg/kg (scPTZ) and N‐[{4‐(3,4‐dichlorophenyl)‐piperazin‐1‐yl}‐methyl]‐pyrrolidine‐2,5‐dione (23) with ED50 = 37.79 mg/kg (MES), ED50 = 128.82 mg/kg (scPTZ), whereas N‐[{4‐(3‐trifluoromethylphenyl)‐piperazin‐1‐yl}‐methyl]‐pyrrolidine‐2,5‐dione (24) was effective only in the MES test with ED50 = 16.37 mg/kg. These molecules showed higher potency and also lower neurotoxicity than the reference antiepileptic drugs such as ethosuximide and valproic acid.