Grażyna Chłoń-Rzepa

Antidepressant- and anxiolytic-like activity of 7-phenylpiperazinylalkyl-1,3-dimethyl-purine-2,6-dione derivatives with diversified 5-HT1A receptor functional profile

Continuing our earlier study in a group of purine-2,6-dione derivatives of long chain arylpiperazines (LCAPs), a series of 8-unsubstituted 7-phenylpiperazin-4-yl-alkyl (4-14) and 7-tetrahydroisoquinolinyl-alkyl (15-17) analogues were synthesized and their serotonin 5-HT1A, 5-HT2A, 5-HT6, 5-HT7 and dopamine D2 receptor affinities were determined. The study allowed us to identify some potent 5-HT1A receptor ligands with additional moderate affinity for 5-HT2A, 5-HT7 and dopamine D2 receptors. Compounds 9, 12, 13 and 14, with the highest 5HT1A receptor affinity, were selected for further functional in vivo studies and behavioural evaluation of antidepressant- and antianxiety-like activity. Compounds 9, 12 and 13 showed features of agonists of pre- and/or post-synaptic 5-HT1A receptors, whereas 14 was classified as an antagonist of postsynaptic sites. Moreover, derivatives 9 and 14 acted as antagonists of 5-HT2A receptors. In behavioural studies, compounds 9 and 13 showed antidepressant-like activity in the mouse forced swim test, and their effects were similar or stronger than those of imipramine. Compounds 9, 12 and 14 displayed potential anxiolytic-like properties in the mouse four-plate test, similar or even greater than those of the reference anxiolytic drug, diazepam.

New 8-aminoalkyl derivatives of purine-2,6-dione with arylalkyl, allyl or propynyl substituents in position 7, their 5-HT1A, 5-HT2A, and 5-HT7 receptor affinity and pharmacological evaluation

BACKGROUND Our previous studies in a group of arylpiperazine derivatives of 1,3-dimethyl-3,7-dihydro-purine-2,6-diones, aimed at chemical diversification of the purine-2,6-dione by introduction of hydrophobic substituent in a 7- or 8- position or elongation of the linker length between arylpiperazine and purine core, allowed a selection of potent 5-HT1A, 5-HT2A and 5-HT7 receptor ligands displaying anxiolytic and antidepressant properties. Continuing our research in this field, in the present studies we designed a new series of 8-aminoalkylamino (15-35) and 8-arylpiperazinylpropoxy (36-42) derivatives of 7-substituted 1,3-dimethyl-3,7-dihydropurine-2,6-dione as potential 5-HT1A, 5-HT2A and 5-HT7 receptor ligands with potential psychotropic activity. METHODS Radioligand binding assays were employed for determining the affinity and the selectivity profile of the synthesized compounds for native 5-HT1A, 5-HT2A, and cloned 5-HT6 and 5-HT7 receptors. The functional activity of the selected compounds at 5-HT1A and 5-HT2A receptors was tested in the commonly used in vivo models. Antidepressant and anxiolytic properties were evaluated in the forced swim (FST) and the four-plate test (FPT) in mice, respectively. RESULTS Among the evaluated series, selected 7-benzyl-8-((4-(4-(3-chlorophenyl)piperazin-1-yl)butyl)amino)-1,3-dimethyl-1H-purine-2,6(3H,7H)-dione (21), a mixed 5-HT1A/5-HT2A/5-HT7 receptor ligand, produced an antidepressant-like effect in FST, and exerted anxiolytic-like activity in FPT. Another pharmacologically evaluated compound 42 (a mixed 5-HT1A/5-HT7 ligand) slightly, but non-significantly attenuated the immobility time of mice in FST and was devoid of activity in FPT. CONCLUSIONS Study revealed advantage of mixed 5-HT1A/5-HT2A/5-HT7 receptor ligands over 5-HT1A/5-HT7 agents to display antidepressant- and anxiolytic-like activity. Modification of arylalkyl/allyl substituent in position 7 of purine-2,6-dione opens possibility for designing new 5-HT ligands with preserved p electron system and lower molecular weight.

7-3-Chlorophenypiperazinylalkyl derivatives of 8-alkoxy-purine-2, 6-dione as a serotonin receptor ligands with potential antidepressant activity

BACKGROUND The previous study showed that arylpiperazine can condition affinity to α-adrenoceptors, 5-HT1A/5-HT2A receptors and compounds with arylpiperazine had antidepressant-like effect. The aim of this study was to determine the antidepressant-like activity of new arylpiperazines containing novel 8-alkoxy-purine-2,6-dione fragments. METHODS New 3-chloroarylpiperazinylalkyl analogs of 8-alkoxy-purine-2,6-dione and their purine-2,6,8-trione analogs (2-5) were tested for their α1, α2, 5-HT1A,5-HT2A, and 5-HT7 receptor affinities in radioreceptor binding study. Moreover, in search for potential antidepressant properties of these compounds, the forced swim test in mice was conducted. RESULTS Compounds 2 and 3 were potent 5-HT1A receptor ligands with Ki within the range on 12-15 nM. All investigated compounds were found to be highly active 5-HT2A receptor (Ki 15-28 nM) and α1 adrenoceptor (Ki 21-89 nM) ligands. In the forced swim test all the compounds showed a significantly activity in spite of their reducing ability of locomotor activity. The most potent effect was produced by compound 4 and 5, which reduced the immobility time in this test in all used doses. CONCLUSION In our study the most potent antidepressant-like activity was produced by compounds 4 and 5, which are selective for the 5-HT2A and α1 receptors.

Analgesic and anti-inflammatory activity of 7-substituted purine-2,6-diones

BACKGROUND In an effort to develop new analgesic and anti-inflammatory agents, we determined a series of 7-substituted purine-2,6-diones. METHODS The obtained compounds (1-6) were evaluated pharmacologically in four in vivo models: the writhing syndrome, the formalin tests, the carrageenan-induced edema model and the zymosan-induced peritonitis. The influence of the investigated compounds on the phosphodiesterase (PDE) and PDE4B activity was also determined. In addition, determination of the antioxidant activity was determined by the FRAP assay. RESULTS A majority of the tested compounds showed a significant analgesic and anti-inflammatory activity. The strongest analgesic and anti-inflammatory effect was observed for 1 and 2. The active compound 1 was more efficient than theophylline in inhibiting the PDE and more efficient than rolipram in inhibiting the PDE4B activity. The tested compounds did not show significant antioxidant properties. CONCLUSION Active compounds (1-6) inhibited the PDE activity, while compound 1 significantly inhibited the PDE4B activity, what may suggest that this mechanism may be involved in their analgesic/anti-inflammatory properties.

Arylpiperazinylalkyl derivatives of 8-amino-1,3-dimethylpurine-2,6-dione as novel multitarget 5-HT/D receptor agents with potential antipsychotic activity.

Abstract A series of new 7-arylpiperazinylalkyl-1,3-dimethyl-purine-2,6-dione derivatives with diversified 8-amino substituent in 8 position was synthesized and their 5-HT1A, 5-HT2A, 5-HT6, 5-HT7, and D2 receptor affinities were determined. The binding study allowed identifying some potent 5-HT1A/5-HT2A/5-HT7/D2 ligands. The most interesting because of their multireceptor profile were 8-piperidine (30–35) and 8-dipropylamine (45–47) analogs with four and five carbon aliphatic linkers. The selected compounds 24, 31, 34, 39, 41, 43, 45, and 46 in the functional in vitro evaluation for all targeted receptors showed significant partial D2 agonist, partial 5-HT1A agonist, and 5-HT2A antagonist properties. The advantageous in vitro affinity of compound 34 for 5-HT1A and D2 receptors has been explained by means of molecular modeling, taking into consideration its partial agonist activity towards the latter one. In behavioral studies, compounds 32 and 34 revealed antipsychotic-like properties, significantly decreasing d-amphetamine-induced hyperactivity in mice.

Analgesic activity of new 8-methoxy-1,3-dimethyl-2,6-dioxo-purin-7-yl derivatives with carboxylic, ester or amide moieties

BACKGROUND The previous studies in a group of 4-arylpiperazinylalkyl derivatives of purine-2,6-dione and several other heterocyclic systems revealed their analgesic properties. In an effort to establish new analgesic agents we designed and synthesized a series of new 8-methoxy-1,3-dimethyl-2,6-dioxo-purin-7-yl derivatives with terminal carboxylic, ester or amide moieties. METHODS The obtained compounds were evaluated pharmacologically in two in vivo models: the writhing syndrome and the formalin tests. The influence of the investigated compounds on the phosphodiesterase (PDE) activity was also determined. RESULTS Majority of the tested compounds showed significant analgesic activity. The strongest analgesic and anti-inflammatory effect were observed for benzylamide (10) and 4-phenylpiperazinamide (11-14) derivatives which were more active than acetylic acid used as a reference drug (up to 23 and 36 fold increase in activity in writhing and formalin test, respectively). Several active compounds stronger than theophylline inhibited the phosphodiesterase activity. CONCLUSION The present study revealed that the presented compounds are new class of analgesic and anti-inflammatory agents and are worthy of the further evaluation regarding to their pharmacological properties.

New Arylpiperazinylalkyl Derivatives of 8‐Alkoxy‐purine‐2,6‐dione and Dihydro[1,3]oxazolo[2,3‐f]purinedione Targeting the Serotonin 5‐HT1A/5‐HT2A/5‐HT7 and Dopamine D2 Receptors

To obtain potential antidepressants and/or antipsychotics, a series of new long‐chain arylpiperazine derivatives of 8‐alkoxy‐purine‐2,6‐dione (10–24) and dihydro[1,3]oxazolo[2,3‐f]purinedione (30–34) were synthesized and their serotonin (5‐HT1A, 5‐HT2A, 5‐HT6, 5‐HT7) and dopamine (D2) receptor affinities were determined. The study allowed the identification of some potent 5‐HT1A/5‐HT7/D2 ligands with moderate affinity for 5‐HT2A sites. The binding mode of representative compounds from both chemical classes (11 and 31) in the site of 5‐HT1A receptor was analyzed in computational studies. In functional in vitro studies, the selected compounds 15 and 16 showed antagonistic properties for the evaluated receptors. 8‐Methoxy‐7‐{4‐[4‐(2‐methoxyphenyl)‐piperazin‐1‐yl]‐butyl}‐1,3‐dimethyl‐purine‐2,6‐dione (15) showed a lack of activity in terms and under the conditions of the forced swim, four plate and amphetamine‐induced hyperactivity tests in mice, probably as a result of its high first pass effect in the liver.

Structure-5-HT receptor affinity relationship in a new group of 7-arylpiperazynylalkyl and 7-tetrahydroisoquinolinylalkyl derivatives of 8-amino-1,3-dimethyl-1H-purine-2,6(3H,7H)-dione.

In our previous paper, we have reported that some 8‐alkoxy‐1,3‐dimethyl‐1H‐purine‐2,6(3H,7H)‐dione derivatives possessed high affinity and displayed agonistic activity for the serotonin 5‐HT1A receptor. In order to examine the influence of the substituent in the position 8 of the purine moiety on the affinity for the serotonin 5‐HT1A, 5‐HT2A, and 5‐HT7 receptors, a series of 7‐arylpiperazynylalkyl and 7‐tetrahydroisoquinolinylalkyl (THIQ) derivatives of 8‐amino‐1,3‐dimethyl‐1H‐purine‐2,6(3H,7H)‐dione were synthesized. All the final compounds were investigated in in vitro competition binding experiments for serotonin 5‐HT1A, 5‐HT2A, and 5‐HT7 receptors. The structure–affinity relationships for this group of compounds were discussed. For selected compounds, functional assays for the 5‐HT1A receptor were carried out. The results of the assays indicated that these groups of derivatives possessed antagonistic activity for this receptor.

Aminoalkyl Derivatives of 8-Alkoxypurine-2,6-diones: Multifunctional 5-HT1A/5-HT7 Receptor Ligands and PDE Inhibitors with Antidepressant Activity

In the search for potential psychotropic agents, a new series of 3,7‐dimethyl‐ and 1,3‐dimethyl‐8‐alkoxypurine‐2,6‐dione derivatives of arylpiperazines, perhydroisoquinolines, or tetrahydroisoquinolines with flexible alkylene spacers (5–16 and 21–32) were synthesized and evaluated for 5‐HT1A/5‐HT7 receptor affinities as well as PDE4B1 and PDE10A inhibitory properties. The 1‐(4‐(4‐(2‐hydroxyphenyl)piperazin‐1‐yl)butyl)‐3,7‐dimethyl‐8‐propoxypurine‐2,6‐dione (16) and 7‐(2‐hydroxyphenyl)piperazinylalkyl‐1,3‐dimethyl‐8‐ethoxypurine‐2,6‐diones (31 and 32) as potent dual 5‐HT1A/5‐HT7 receptor ligands with antagonistic activity produced an antidepressant‐like effect in the forced swim test in mice. This effect was similar to that produced by citalopram. All the tested compounds were stronger phosphodiesterase isoenzyme inhibitors than theophylline and theobromine. The most potent compounds, 15 and 16, were characterized by 51 and 52% inhibition, respectively, of PDE4B1 activity at a concentration of 10−5 M. Concerning the above findings, it may be assumed that the inhibition of PDE4B1 may impact on the signal strength and specificity resulting from antagonism toward the 5‐HT1 and 5‐HT7 receptors, especially in the case of compounds 15 and 16. This dual receptor and enzyme binding mode was analyzed and explained via molecular modeling studies.

In Vitro Biotransformation, Safety, and Chemopreventive Action of Novel 8-Methoxy-Purine-2,6-Dione Derivatives

Metabolic stability, mutagenicity, antimutagenicity, and the ability to scavenge free radicals of four novel 8-methoxy-purine-2,6-dione derivatives (compounds 1–4) demonstrating analgesic and anti-inflammatory properties were determined. Metabolic stability was evaluated in Cunninghamella and microsomal models, mutagenic and antimutagenic properties were assessed using the Ames and the Vibrio harveyi tests, and free radical scavenging activity was evaluated with 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay. In the Cunninghamella model, compound 2 did not undergo any biotransformation; whereas 3 and 4 showed less metabolic stability: 1–9 and 53–88% of the parental compound, respectively, underwent biotransformation reactions in different Cunninghamella strains. The metabolites detected after the biotransformation of 3 and 4 were aromatic hydroxylation and N-dealkylation products. On the other hand, the N-dealkylation product was the only metabolite formed in microsome assay. Additionally, these derivatives do not possess mutagenic potential in microbiological models (Vibrio harveyi and Salmonella typhimurium) considered. Moreover, all compounds showed a strong chemopreventive activity in the modified Vibrio harveyi strains BB7X and BB7M. However, radical scavenging activity was not the mechanism which explained the observed chemopreventive activity.