The novel trisubstituted pyran derivative D-142 has triple monoamine reuptake inhibitory activity and exerts potent antidepressant-like activity in rodents

Design Strategies, Chemistry and Therapeutic Insights of Multi-target Directed Ligands as Antidepressant Agents

Depression is one of the major disorders of the central nervous system worldwide and causes disability and functional impairment. According to the World Health Organization, around 265 million people worldwide are affected by depression. Currently marketed antidepressant drugs take weeks or even months to show anticipated clinical efficacy but remain ineffective in treating suicidal thoughts and cognitive impairment. Due to the multifactorial complexity of the disease, single-target drugs do not always produce satisfactory results and lack the desired level of therapeutic efficacy. Recent literature reports have revealed improved therapeutic potential of multi-target directed ligands due to their synergistic potency and better safety. Medicinal chemists have gone to great extents to design multitarget ligands by generating structural hybrids of different key pharmacophores with improved binding affinities and potency towards different receptors or enzymes. This article has compiled the design strategies of recently published multi-target directed ligands as antidepressant agents. Their biological evaluation, structural-activity relationships, mechanistic and in silico studies have also been described. This article will prove to be highly useful for the researchers to design and develop multi-target ligands as antidepressants with high potency and therapeutic efficacy.

Novel Potent Dopamine-Norepinephrine and Triple Reuptake Uptake Inhibitors Based on Asymmetric Pyran Template and Their Molecular Interactions with Monoamine Transporters

We have carried out a structural exploration of (2S,4R,5R)-2-(bis(4-fluorophenyl)methyl)-5-((4-methoxybenzyl)amino)tetrahydro-2H-pyran-4-ol (D-473) to investigate the influence of various functional groups on its aromatic ring, the introduction of heterocyclic aromatic rings, and the alteration of the stereochemistry of functional group on the pyran ring. The novel compounds were tested for their affinities for the dopamine transporter (DAT), serotonin transporter (SERT), and norepinephrine transporter (NET) in the brain by measuring their potency in inhibiting monoamine neurotransmitter uptake. Our studies identified some of the most potent dopamine-norepinephrine reuptake inhibitors known to-date like D-528 and D-529. The studies also led to development of potent triple reuptake inhibitors such as compounds D-544 and D-595. A significant influence from the alteration of the stereochemistry of the hydroxyl group on the pyran ring of D-473 on transporters affinities was observed indicating stereospecific preference for interaction. The inhibitory profiles and structure-activity relationship of lead compounds were further corroborated by molecular docking studies at the primary binding sites of monoamine transporters. The nature of interactions found computationally correlated well with their affinities for the transporters.

Hybrids of Coumarin Derivatives as Potent and Multifunctional Bioactive Agents: A Review

BACKGROUND

Coumarins exhibit a plethora of biological activities, e.g. antiinflammatory and anti-tumor. Molecular hybridization technique has been implemented in the design of novel coumarin hybrids with several bioactive groups in order to obtain molecules with better pharmacological activity and improved pharmacokinetic profile.

OBJECTIVE

Therefore, we tried to gather as many as possible biologically active coumarin hybrids referred in the literature till now, to delineate the structural characteristics in relation to the activities and to have a survey that might help the medicinal chemists to design new coumarin hybrids with drug-likeness and varied bioactivities.

RESULTS

The biological activities of the hybrids in most of the cases were found to be different from the biological activities presented by the parent coumarins. The results showed that the hybrid molecules are more potent compared to the standard drugs used in the evaluation experiments.

CONCLUSION

Conjugation of coumarin with varied pharmacophore groups/druglike molecules responsible for different biological activities led to many novel hybrid molecules, with a multitarget behavior and improved pharmacokinetic properties.

Revisiting the validity of the mouse tail suspension test: Systematic review and meta-analysis of the effects of prototypic antidepressants

Animal models in neuropsychiatric research need validation. One way to address external validity is systematic reviews and meta-analyses. The present study presents a meta-analysis of the effects of antidepressants in the mouse tail suspension test (TST). A PubMed search identified studies that examined imipramine and fluoxetine effects in the TST. Inclusion criteria were testing in the light phase; trial duration was six minutes; immobility time scored 6 or (last) 4 min; adult mice; acute intraperitoneal (IP) administration. Effect sizes (ES) were estimated using Cohen's d, heterogeneity of ES with Cochran's Q test, correlations between dose and ES with Pearson's correlation and differences between strains with Analysis of variance. Results show that antidepressants decrease immobility time in the TST and a correlation between drug dose and ES but no effects of strain. We suggest that the TST is a valid tool to quantitatively, consistently and reproducibly capture the immobility-reducing aspects of fluoxetine and imipramine and that the lack of strain effects is due to small number of experiments in many of the strains.

Efficient and Green Synthesis of 2,2′-(Arylmethylene)Bis-4-Pyrones in an Ionic Liquid [bmim+][BF4–]

A series of sixteen 2,2′-(arylmethylene)bis(3-hydroxy-6-methyl-4H-pyran-4-ones) have been prepared in high yield via an ammonium acetate-catalysed three-component reaction of an aromatic aldehyde (1 equiv.) and allomaltol (2 equiv.) in an ionic liquid [bmim+][BF4–]. The reaction work-up is simple and the ionic liquid can be easily separated from the product and reused.

The endocannabinoid system and NGF are involved in the mechanism of action of resveratrol: a multi-target nutraceutical with therapeutic potential in neuropsychiatric disorders

RATIONALE

Resveratrol is a polyphenolic compound with antioxidant, anti-inflammatory, and neuroprotective effects. It has also shown antidepressant-like effects in the behavioral studies; however, its mechanism(s) of action merit further evaluation.

OBJECTIVES

The interaction between the nerve growth factor (NGF) and endocannabinoid system (eCBs) and their contribution to the antidepressant or emotional activity prompted us to evaluate their implications in the mechanism of action of resveratrol.

METHODS

After single and 4-week intraperitoneal (i.p.) once-daily injections of resveratrol (40, 80, and 100 mg/kg), amitriptyline (2.5, 5, and 10 mg/kg), or clonazepam (10, 20, and 40 mg/kg) into male Wistar rats, eCB and NGF contents were quantified in the brain regions implicated in the modulation of emotions by isotope-dilution liquid chromatography/mass spectrometry and Bio-Rad protein assay, respectively. In the case of any significant alteration of brain eCB or NGF level, the effect of pre-treatment with cannabinoid CB1 or CB2 receptor antagonist (AM251 or SR144528) was investigated.

RESULTS

Four-week treatment with resveratrol or amitriptyline resulted in a significant and sustained enhancement of NGF and eCB contents in dose-dependent and brain region-specific manner. Neither acute nor 4-week treatment with clonazepam affected brain eCB or NGF contents. Pre-treatment with AM251 (3 mg/kg), but not SR144528, prevented the enhancement of NGF protein levels. AM251 exhibited no effect by itself.

CONCLUSIONS

Resveratrol like the classical antidepressant, amitriptyline, affects brain NGF and eCB signaling under the regulatory drive of CB1 receptors.

Triple reuptake inhibitors as potential next-generation antidepressants: a new hope?

The current therapy for depression is less than ideal with remission rates of only 25-35% and a slow onset of action with other associated side effects. The persistence of anhedonia originating from depressed dopaminergic activity is one of the most treatment-resistant symptoms of depression. Therefore, it has been hypothesized that triple reuptake inhibitors (TRIs) with potency to block dopamine reuptake in addition to serotonin and norepinephrine transporters should produce higher efficacy. The current review comprehensively describes the development of TRIs and discusses the importance of evaluation of in vivo transporter occupancy of TRIs, which should correlate with efficacy in humans.

Development of potent dopamine-norepinephrine uptake inhibitors (DNRIs) based on a (2S,4R,5R)-2-benzhydryl-5-((4-methoxybenzyl)amino)tetrahydro-2H-pyran-4-ol molecular template

Current therapy of depression is less than ideal with remission rates of only 25-35% and response rates of 45-60%. It has been hypothesized that a dysfunctional dopaminergic system in the mesocorticolimbic pathway in depressive disorder may lead to development of anhedonia associated with loss of pleasure and interest along with loss of motivation. The current antidepressants do not address dopamine dysfunction which might explain their low efficacy. In this report, we have described an SAR study on our pyran-based triple reuptake inhibitors (TRIs) which are being investigated as the next-generation antidepressants. In the present work we demonstrate that our lead TRIs can be modified with appropriate aromatic substitutions to display a highly potent SSRI profile for compounds 2a and 4a (Ki (SERT); 0.71 and 2.68nM, respectively) or a potent DNRI profile for compounds 6b and 6h (Ki (DAT/NET); 8.94/4.76 and 13/7.37nM, respectively). Compounds 4g-4i exhibited potencies at all three monoamine transporters. The results provide insights into the structural requirements for developing selective dual- and triple-uptake inhibitors from a unique pyran molecular template for an effective management of depression and related disorders.

Pharmacological and behavioral characterization of D-473, an orally active triple reuptake inhibitor targeting dopamine, serotonin and norepinephrine transporters

Major depressive disorder (MDD) is a debilitating disease affecting a wide cross section of people around the world. The current therapy for depression is less than adequate and there is a considerable unmet need for more efficacious treatment. Dopamine has been shown to play a significant role in depression including production of anhedonia which has been one of the untreated symptoms in MDD. It has been hypothesized that drugs acting at all three monoamine transporters including dopamine transporter should provide more efficacious antidepressants activity. This has led to the development of triple reuptake inhibitor D-473 which is a novel pyran based molecule and interacts with all three monoamine transporters. The monoamine uptake inhibition activity in the cloned human transporters expressed in HEK-293 cells (70.4, 9.18 and 39.7 for DAT, SERT and NET, respectively) indicates a serotonin preferring triple reuptake inhibition profile for this drug. The drug D-473 exhibited good brain penetration and produced efficacious activity in rat forced swim test under oral administration. The optimal efficacy dose did not produce any locomotor activation. Microdialysis experiment demonstrated that systemic administration of D-473 elevated extracellular level of the three monoamines DA, 5-HT, and NE efficaciously in the dorsal lateral striatum (DLS) and the medial prefrontal cortex (mPFC) area, indicating in vivo blockade of all three monoamine transporters by D-473. Thus, the current biological data from D-473 indicate potent antidepressant activity of the molecule.

Design and synthesis of new series of coumarin-aminopyran derivatives possessing potential anti-depressant-like activity

A new series of coumarin based aminopyran derivatives were designed, synthesized and evaluated for their preclinical antidepressant effect on Swiss albino mice. Among the series, compounds 21, 25, 26, 27, 32 and 33 exhibited significant activity profile in forced swimming test (FST). Compound 27 was most efficacious, which at a very low dose of 0.5mg/kg reduced the time of immobility by 86.5% as compared to the standard drug fluoxetine (FXT) which reduced the immobility time by 69.8% at the dose of 20mg/kg, ip. In addition, all active compounds were screened in dose dependent manner (at doses of 0.25, 0.5, 1mg/kg ip) in FST and tail suspension test (TST). Interestingly, all active compounds did not caused any significant alteration of locomotor activity in mice as compared to control, indicating that the hybrids did not produce any motor impairment effects. The results indicate that coumarin-aminopyran derivatives may have potential therapeutic value for the management of mental depression.

Flexible and biomimetic analogs of triple uptake inhibitor 4-((((3S,6S)-6-benzhydryltetrahydro-2H-pyran-3-yl)amino)methyl)phenol: Synthesis, biological characterization, and development of a pharmacophore model

In this study we have generated a pharmacophore model of triple uptake inhibitor compounds based on novel asymmetric pyran derivatives and the newly developed asymmetric furan derivatives. The model revealed features important for inhibitors to exhibit a balanced activity against dopamine transporter (DAT), serotonin transporter (SERT), and norepinephrine transporter (NET). In particular, a 'folded' conformation was found common to the active pyran compounds in the training set and was crucial to triple uptake inhibitory activity. Furthermore, the distances between the benzhydryl moiety and the N-benzyl group as well as the orientation of the secondary nitrogen were also important for TUI activity. We have validated our findings by synthesizing and testing novel asymmetric pyran analogs. The present work has also resulted in the discovery of a new series of asymmetric tetrahydrofuran derivatives as novel TUIs. Lead compounds 41 and 42 exhibited moderate TUI activity. Interestingly, the highest TUI activity by lead tetrahydrofuran compounds for example, 41 and 42, was exhibited in a stereochemical preference similar to pyran TUI for example, D-161.

Structural exploration of (3S,6S)-6-benzhydryl-N-benzyltetrahydro-2H-pyran-3-amine analogues: identification of potent triple monoamine reuptake inhibitors as potential antidepressants

To further explore the basic structural motifs (3S,6S)-6-benzhydryl-N-benzyltetrahydro-2H-pyran-3-amine and (2S,4R,5R)-2-benzhydryl-5-(benzylamino)tetrahydro-2H-pyran-4-ol, developed by our research group, for monoamine transport inhibition, we designed and synthesized various structurally altered analogues. The new compounds were tested for their affinities for the dopamine transporter (DAT), the serotonin transporter (SERT), and the norepinephrine transporter (NET) in rat brain by measuring their capacity to inhibit the uptake of [(3)H]DA, [(3)H]5-HT, and [(3)H]NE, respectively. Our results point to novel compounds with a TUI, DNRI, SNRI, or SSRI profile. Among the TUIs, compound 2 g exhibited a balanced potency for all three monoamine transporters (K(i): 60, 79, and 70.3 nM for DAT, SERT, and NET, respectively). In the rat forced swim test, compound 2 g produced a significant decrease in immobility in drug-treated rats relative to vehicle, indicating a potential antidepressant property.