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The crystal structure of the dopamine D3 receptor (D3R) in complex with eticlopride inspired the design of bitopic ligands that explored (1) N-alkylation of the eticlopride's pyrrolidine ring, (2) shifting of the position of the pyrrolidine nitrogen, (3) expansion of the pyrrolidine ring system, and (4) incorporation of O-alkylations at the 4-position. Structure activity relationships (SAR) revealed that moving the N- or expanding the pyrrolidine ring was detrimental to D2R/D3R binding affinities. Small pyrrolidine N-alkyl groups were poorly tolerated, but the addition of a linker and secondary pharmacophore (SP) improved affinities. Moreover, O-alkylated analogues showed higher binding affinities compared to analogously N-alkylated compounds, e.g., O-alkylated 33 (D3R, 0.436 nM and D2R, 1.77 nM) vs the N-alkylated 11 (D3R, 6.97 nM and D2R, 25.3 nM). All lead molecules were functional D2R/D3R antagonists. Molecular models confirmed that 4-position modifications would be well-tolerated for future D2R/D3R bioconjugate tools that require long linkers and or sterically bulky groups. more...

The need for safer pain-management therapies with decreased abuse liability inspired a novel drug design that retains μ-opioid receptor (MOR)-mediated analgesia, while minimizing addictive liability. We recently demonstrated that targeting the dopamine D3 receptor (D3R) with highly selective antagonists/partial agonists can reduce opioid self-administration and reinstatement to drug seeking in rodent models without diminishing antinociceptive effects. The identification of the D3R as a target for the treatment of opioid use disorders prompted the idea of generating a class of ligands presenting bitopic or bivalent structures, allowing the dual-target binding of the MOR and D3R. Structure-activity relationship studies using computationally aided drug design and in vitro binding assays led to the identification of potent dual-target leads (23, 28, and 40), based on different structural templates and scaffolds, with moderate (sub-micromolar) to high (low nanomolar/sub-nanomolar) binding affinities. Bioluminescence resonance energy transfer-based functional studies revealed MOR agonist-D3R antagonist/partial agonist efficacies that suggest potential for maintaining analgesia with reduced opioid-abuse liability. more...

The non-medical use of opioids has become a national crisis in the USA. Developing non-opioid pharmacotherapies for controlling this opioid epidemic is urgent. Dopamine D

The crystal structure of the dopamine D(3) receptor (D(3)R) in complex with eticlopride inspired the design of bitopic ligands that explored 1) N-alkylation of eticlopride’s pyrrolidine ring, 2) shifting the position of the pyrrolidine nitrogen, 3) expanding the pyrrolidine ring system, and 4) incorporating O-alkylations at the 4-position. Structure Activity Relationships (SAR) revealed that moving the N- or expanding the pyrrolidine ring was detrimental to D(2)R/D(3)R binding affinities. Small pyrrolidine N-alkyl groups were poorly tolerated, but addition of a linker and secondary pharmacophore (SP) improved affinities. Moreover, O-alkylated analogues showed higher binding affinities compared to analogously N-alkylated compounds, e.g., O-alkylated 33 (D(3)R, 0.436 nM and D(2)R, 1.77 nM) vs. the N-alkylated 11 (D(3)R, 6.97 nM and D(2)R, 25.3 nM). All lead molecules were functional D(2)R/D(3)R antagonists. Molecular models confirmed that 4-position modifications would be well-tolerated for future D(2)R/D(3)R bioconjugate tools that require long linkers and or sterically bulky groups. more...

Opioid and cocaine abuse are major public health burdens. Existing medications for opioid use disorder are limited by abuse liability and side effects, whereas no treatments are currently approved in the United States for cocaine use disorder. Dopamine D(3) receptor (D(3)R) antagonists have shown promise in attenuating opioid and cocaine reward and mitigating relapse in preclinical models. However, translation of D(3)R antagonists to the clinic has been hampered by reports that the D(3)R antagonists GSK598,809 (5-(5-((3-((1S,5R)-1-(2-fluoro-4-(trifluoromethyl)phenyl)-3-azabicyclo[3.1.0]hexan-3-yl)propyl)thio)-4-methyl-4H-1,2,4-triazol-3-yl)-4-methyloxazole) and SB-277,011A (2-(2-((1r,4r)-4-(2-oxo-2-(quinolin-4-yl)ethyl)cyclohexyl)ethyl)-1,2,3,4-tetrahydroisoquinoline-6-carbonitrile) have adverse cardiovascular effects in the presence of cocaine. Recently, we developed two structurally novel D(3)R antagonists, R-VK4-40 and R-VK4-116, which are highly selective for D(3)R and display translational potential for treatment of opioid use disorder. Here, we tested whether R-VK4-40 ((R)-N-(4-(4-(2-Chloro-3-ethylphenyl)piperazin-1-yl)-3-hydroxybutyl)-1H-indole-2-carboxamide) and R-VK4-116 ((R)-N-(4-(4-(3-Chloro-5-ethyl-2-methoxyphenyl)piperazin-1-yl)-3-hydroxybutyl)-1H-indole-2-carboxamide) have unwanted cardiovascular effects in the presence of oxycodone, a prescription opioid, or cocaine in freely moving rats fitted with surgically implanted telemetry transmitters. We also examined cardiovascular effects of the D(3)R antagonist, SB-277,011A, and L-741,626 (1-((1H-indol-3-yl)methyl)-4-(4-chlorophenyl)piperidin-4-ol), a dopamine D(2) receptor–selective antagonist, for comparison. Consistent with prior reports, SB-277,011A increased blood pressure, heart rate, and locomotor activity alone and in the presence of cocaine. L-741,626 increased blood pressure and heart rate. In contrast, R-VK4-40 alone dose-dependently reduced blood pressure and heart rate and attenuated oxycodone-induced increases in blood pressure and oxycodone or cocaine-induced increases in heart rate. Similarly, R-VK4-116 alone dose-dependently reduced cocaine-induced increases in blood pressure and heart rate. These results highlight the safety of new D(3)R antagonists and support the continued development of R-VK4-40 and R-VK4-116 for the treatment of opioid and cocaine use disorders. SIGNIFICANCE STATEMENT: Opioid and cocaine abuse are major public health challenges and new treatments that do not adversely impact the cardiovascular system are needed. Here, we show that two structurally novel dopamine D(3) receptor antagonists, R-VK4-40 and R-VK4-116, do not potentiate, and may even protect against, oxycodone- or cocaine-induced changes in blood pressure and heart rate, supporting their further development for the treatment of opioid and/or cocaine use disorders. more...

Because of the large degree of homology among dopamine D2-like receptors, discovering ligands capable of discriminating between the D2, D3, and D4 receptor subtypes remains a significant challenge.... more...

Literature reports suggest that pyrazoles and hydrazides are potential antimicrobial pharmocophores. Considering this fact, a series of nineteen conjugates containing hybrids of bis-pyrazole scaffolds joined through a hydrazide linker were synthesized and further evaluated for their antimicrobial activity against a panel of Gram-positive and Gram-negative bacteria along with Candida albicansMTCC 3017 strain. Although the derivatives exhibited good antibacterial activity, some of the derivatives (13d, 13j, 13l, 13p, and 13r) showed excellent anti-Candida activity with MICs values of 3.9 μg/ml, which was equipotent to that of the standard Miconazole (3.9 μg/ml), which has inspired us to further explore their anti-Candida activity. The same compounds were also tested for anti-biofilm studies against various Candida strains and among them, compounds 13l and 13r efficiently inhibited the formation of fungal biofilms. Field emission scanning electron micrographs revealed that one of the promising compound 13r showed cell damage and in turn cell death of the Candida strain. These potential conjugates (13l and 13r) also demonstrated promising ergosterol biosynthesis inhibition against some of the strains C. albicans, which were further validated through molecular docking studies. In silico computational studies were carried out to predict the binding modes and pharmacokinetic parameters of these conjugates. more...

Microbes possess a vast reservoir of bioactive compounds, including cyclic lipopeptides (CLPs). In the present study, an exopolymeric biosurfactant composed of lipoheptapeptides was isolated and identified from a marine algicolous bacterial isolate, Bacillus atrophaeus strain AKLSR1, endophytic to Padina tetrastromatica. The lipopeptides were characterized by using FT-IR, NMR, GC–MS and UPLC-ESI-Q-Tof-MS/MS spectroscopic studies. Structural analysis unveiled five CLP variants that formed one major polymeric lipopeptide. These cyclic lipoheptapeptides represent a new class of surfactin family, with significant variations in the fatty acid chain length and amino acid substitutions in the peptide moiety as compared to standard lipopeptides of surfactin family. The critical micelle concentration of this biosurfactant is 0.9 mg L−1 at a surface tension of 28 mN m−1. Polymeric biosurfactant showed stable emulsification index against various organic solvents and vegetable oils. CLPs showed substantial mortality of different cancer cell lines but no toxicity towards normal human lung cell line, MRC5. Further, mechanistic studies revealed cell cycle arrest, ROS accumulation, nuclear fragmentation and cell death. Our studies indicated that CLPs induced apoptosis in lung carcinoma cell line, A549. Anti-proliferative effect of CLPs produced by marine algicolous B. atrophaeus strain AKLSR1 suggests that it could be further explored for biomedical applications. more...

Marine microbes secrete exopolymeric substances (EPS), which surrounds the biofilm and inhibits the fungal growth. Elucidation of the structure and function of the extracellular exopolymeric substances is of vital relevance therapeutically. The active compound responsible for bioactivity was purified and characterized using TLC, LC/MS/MS, GC/MS and FT-IR. Bioactivity of the characterized cyclic peptides (CLPs) against azole resistant and susceptible Candida strains were examined for growth and biofilm formation using scanning electron microscopy, flow cytometry, confocal microscopy. In the present study we identified bioactive cyclic peptides from marine isolated Neobacillus drentensis that exhibited promising tensio-active properties and antifungal efficacy against azole resistant and susceptible Candida albicans. The cluster is composed of five CLP isoforms which were sequenced and identified as new peptides with compositional and structural variations in the amino acid sequence and fatty acid chain. In vitro cytotoxic activity of CLPs was tested in human fibroblast normal cells. We have observed that the CLPs repressed the Candida albicans growth and multiplication by inhibiting the biofilm formation and disruption of branching filamentous hyphae. CLPs have been found to arrest the C. albicans cell cycle by a block at G1-S transition followed by apoptotic cell death. The current studies suggest these natural marine derived CLPs function as potential anti-biofilm agents against azole C. albicans resistant strains. more...

In an attempt to develop potent and selective anticancer agents, a series of 15 conjugates of 1,4-dihydroindeno[1,2-c]pyrazole chalcone (12a-o) were designed, synthesized and evaluated for their antiproliferative activity against MCF7, A549, MDA-MB-231, HCT116 and SKBR3 human cancer cell lines. Among them, 12h, 12l and 12m showed IC50 values: 3.82, 5.33 and 4.21 μM, respectively, on A549 cell with respect to the positive control, Erlotinib (IC50 value: 10.26 μM). Detailed biological assays showed accumulation of mitotic cells in G2/M phase. In addition, Western blot analysis and immunofluorescence study revealed inhibition of EGFR and Akt pathways. In silico computational studies were also carried out to predict the binding modes and pharmacokinetic parameters of these conjugates. more...

A series of 1, 4-dihydroindeno-[1,2-c] pyrazole linked oxindole conjugates have been synthesized by using Knoevenagel condensation method and further evaluated for their antiproliferative activity against HeLa, A549 and MDA-MB-231 human cancer cell lines along with HEK-293 (normal human embryonic kidney cells). Among the derivatives, compounds 12a, 12b, and 12d showed excellent cytotoxicity with IC50 values ranging between 1.33 to 4.33 μM. Furthermore, detailed biological assays showed that there was accumulation of mitotic cells in G2/M phase, disruption of microtubule network and increase in the G2/M checkpoint proteins (Cyclin B1 and CDK1). Moreover, compound 12d with IC50 value of 1.33 μM showed significant upregulation of tumor suppressor proteins like p53, p21 and pro-apoptotic Bax. The molecular docking analysis demonstrated that these congeners occupy the colchicine binding pocket of the tubulin. more...

Two novel series comprising of forty two compounds have been synthesized by conjugating quinoline scaffold with chalcone as well as pyrazoline motifs. All the synthesized conjugates were tested for their antibacterial, antifungal and anti-tubercular activities. Several of these novel compounds exhibited good to appreciable antibacterial activity against the tested bacterial strains. Compounds 4 j and 7 b were found to be the promising candidates exhibiting MIC 4 μg/mL against B. subtilisMTCC 121 and M. luteus MTCC 2470. Moreover, several conjugates significantly inhibited growth of certain fungal organisms. Furthermore, some of the conjugates displayed moderate anti-tubercular activity against both H37RV as well as RifR strains. The binding modes and effect of the C4 quinoline substitution on the activity have been studied using computational techniques. Methyl group enhances the antimicrobial activity upon replacement by aromatic phenyl group and this is supported by the experimental data. more...

Dopamine D(3) receptors (D(3)R) play a critical role in neuropsychiatric conditions including substance use disorders (SUD). Recently, we reported a series of N-(3-hydroxy-4-(4-phenylpiperazin-1yl)butyl)-1H-indole-2-carboxamide analogues as high affinity and selective D(3)R lead molecules for the treatment of opioid use disorders (OUD). Further optimization led to a series of analogues that replaced the 3-OH with a 3-F in the linker between the primary pharmacophore (PP) and secondary pharmacophore (SP). Among the 3-F-compounds, 9b demonstrated the highest D(3)R binding affinity (K(i) = 0.756 nM) and was 327-fold selective for D(3)R over D(2)R. In addition, modification of the PP or SP with a 3,4-(methylenedioxy)phenyl group was also examined. Further, an enantioselective synthesis as well as chiral HPLC methods were developed to give enantiopure R- and S-enantiomers of the four lead compounds. Off-target binding affinities, functional efficacies, and metabolic profiles revealed critical structural components for D(3)R selectivity as well as drug-like features required for development as pharmacotherapeutics. more...

Due to the large degree of homology among dopamine D(2)-like receptors, discovering ligands capable of discriminating between the D(2), D(3) and D(4) receptor subtypes remains a significant challenge. Previous work has exemplified the use of bitopic ligands as a powerful strategy in achieving subtype selectivity for agonists and antagonists alike. Inspired by the potential for chemical modification of the D(3) preferential agonists (+)-PD128,907 (1) and PF592,379 (2), we synthesized bitopic structures to further improve their D(3)R selectivity. We found the (2S,5S) conformation of scaffold 2 resulted in a privileged architecture with increased affinity and selectivity for the D(3)R. In addition, a cyclopropyl moiety incorporated into the linker and full resolution of the chiral centers resulted in lead compound 53 and the eutomer 53a that demonstrate significantly higher D(3)R binding selectivities than the reference compounds. Moreover, the favorable metabolic stability in rat liver microsomes supports future studies in in vivo models of dopamine system dysregulation. more...

A series of imidazo[2,1-b]thiazole linked triazole conjugates were synthesized by using Huisgen 1,3-dipolar cyclo-addition reaction (click chemistry approach) and evaluated for their antiproliferative activity against some human cancer cell lines like, HeLa (cervical), DU-145 (prostate), A549 (lung), MCF-7 (breast) and HepG2 (liver). Among them, Conjugates 4g and 4h demonstrated a significant antiproliferative effect against human lung cancer cells (A549) with IC50 values of 0.92 and 0.78 μM respectively. Flow cytometric analysis revealed that these conjugates induced cell cycle arrest in G2/M phase in A549 lung cancer cells. The tubulin polymerization assay and immunofluorescence analysis showed that these conjugates effectively inhibit microtubule assembly in cell free and cell based (A549) experiment respectively. Moreover, the apoptosis inducing properties were evaluated by Hoechst staining, mitochondrial membrane potential and Annexin V-FITC assay. Further, western blot analysis was performed for proapoptotic protein Bax and antiapoptotic protein Bcl-2 and the results demonstrated that there was up regulation of Bax and down regulation of Bcl-2 suggesting that these compounds induced apoptosis in human lung cancer cells, A549. more...

Prescription opioid abuse is a global crisis. New treatment strategies for pain and opioid use disorders are urgently required. We evaluated the effects of R-VK4-40, a highly selective dopamine (DA) D(3) receptor (D(3)R) antagonist, on the rewarding and analgesic effects of oxycodone, the most commonly abused prescription opioid, in rats and mice. Systemic administration of R-VK4-40 dose-dependently inhibited oxycodone self-administration and shifted oxycodone dose-response curves downward in rats. Pretreatment with R-VK4-40 also dose-dependently lowered break-points for oxycodone under a progressive-ratio schedule. To determine whether a DA-dependent mechanism underlies the impact of D(3) antagonism in reducing opioid reward, we used optogenetic approaches to examine intracranial self-stimulation (ICSS) maintained by optical activation of ventral tegmental area (VTA) DA neurons in DAT-Cre mice. Photoactivation of VTA DA in non-drug treated mice produced robust ICSS behavior. Lower doses of oxycodone enhanced, while higher doses inhibited, optical ICSS. Pretreatment with R-VK4-40 blocked oxycodone-enhanced brain-stimulation reward. By itself, R-VK4-40 produced a modest dose-dependent reduction in optical ICSS. Pretreatment with R-VK4-40 did not compromise the antinociceptive effects of oxycodone in rats, and R-VK4-40 alone produced mild antinociceptive effects without altering open-field locomotion or rotarod locomotor performance. Together, these findings suggest R-VK4-40 may permit a lower dose of prescription opioids for pain management, potentially mitigating tolerance and dependence, while diminishing reward potency. Hence, development of R-VK4-40 as a therapy for the treatment of opioid use disorders and/or pain is currently underway. more...

Aiming to develop a new target for the anticancer treatment, a series of 5'H-spiro[indoline-3,4'-pyrrolo [1,2-a]quinoxalin]-2-ones has been synthesized by simple, highly efficient and environmentally friendly method in excellent yields under catalyst-free conditions using ethanol as a green solvent. A simple filtration of the reaction mixture and subsequent drying affords analytically pure products. The synthesized derivatives were evaluated for their antiproliferative activity against five different human cancer cell lines, among the congeners compound 3n showed significant cytotoxicity against the human prostate cancer (DU-145). Flow cytometric analysis revealed that this compound induces cell cycle arrest in the G0/G1 phase and Western blot analysis suggested that reduction in Cdk4 expression level leads to apoptotic cell death. This was further confirmed by mitochondrial membrane potential ((ΔΨm), Annexin V-FITC assay and docking experiments. Furthermore, it was observed that there is an increase in expression levels of cyclin dependent kinase inhibitors like Cip1/p21 and Kip1/p27. more...

A series of twenty one compounds with pyrazole and oxindole conjugates were synthesized by Knoevenagel condensation and investigated for their antiproliferative activity on different human cancer cell lines. The conjugates are comprised of a four ring scaffold; the structural isomers 12b and 12c possess chloro-substitution in the D ring. Among the congeners 12b, 12c, and 12d manifested significant cytotoxicity and inhibited tubulin assembly. Treatments with 12b, 12c and 12d resulted in accumulation of cells in G2/M phase, disruption of microtubule network, and increase in cyclin B1 protein. Zebrafish screening revealed that 12b, and 12d caused developmental defects. Docking analysis demonstrated that the congeners occupy the colchicine binding pocket of tubulin. more...

A series of new (Z)-3-(arylamino)-1-(2-(arylamino)pyridin-3-yl)prop-2-en-1-one conjugates 9a–p were synthesized and evaluated for their cytotoxic activity against some human cancer cell lines. Some of the treated compounds like 9a, 9g and 9j showed significant activity with IC50 values ranging from 0.51 to 1.29 μM. Flow cytometry results revealed that for A549 cells these compounds caused accumulation of cells in the G2/M phase. Interestingly, compound 9a demonstrated a considerable inhibitory effect on tubulin polymerization and showed significant inhibition of tubulin polymerization with an IC50 value of 1.34 μM, whereas nocodazole showed antitubulin activity with an IC50 value 2.64 μM. Further, Hoechst staining and activation of caspase-3 suggested that these conjugates induced cell death by apoptosis. Fluorescence based competitive colchicine binding assay and docking studies suggest that these conjugates 9a and 9g bind to the tubulin perfectly at the colchicine binding site. more...

A series of imidazopyridine/imidazopyrimidine-benzimidazole conjugates (11a–t) were synthesized and evaluated for their antiproliferative activity. All of these conjugates showed moderate to improved cytotoxic activity against the human cervical (Hela), lung (A549), prostate (DU-145) and melanoma (B-16) cancer cell lines. Among them, conjugates 11i and 11p showed significant antiproliferative activity against lung cancer cell line A549 with IC50 values 1.48 and 1.92 μM, respectively. Flow cytometric analysis revealed that these conjugates induced cell cycle arrest at G2/M phase in the A549 cell line leading to caspase-3-dependent apoptotic cell death. The tubulin polymerization assay (IC50 of 11i is 2.06 μM and 11p is 2.26 μM) and immuofluorescence analysis displayed that these conjugates effectively inhibit microtubule assembly at both the molecular and cellular levels in A549 cells. Further, Hoechst staining, caspase-3 activation assay, DNA fragmentation analysis and Annexin V-FITC assay also suggested that these compounds induced cell death by apoptosis. Furthermore, molecular docking studies indicated that these conjugates efficiently interact and bind with tubulin protein. Overall, the present study demonstrates that the synthesis of imidazopyridine/imidazopyrimidine-benzimidazole conjugates as promising tubulin inhibitors with G2/M phasecell cycle arrest and apoptotic-inducing ability. more...

A new class of pyrazole and isoxazole conjugates were synthesized and evaluated for their cytotoxic activity against various human cancer cell lines. These compounds have shown significant cytotoxicity with lower IC50 values. FACS results revealed that A549 cells treated with these compounds arrested cells at the G2/M phase of the cell cycle apart from activating cyclin B1 protein levels. Particularly, compounds 9a and 9b demonstrated a remarkable inhibitory effect on tubulin polymerization and showed a pronounced inhibitory effect on tubulin polymerization with IC50 values of 1.28 μM and 0.28 μM respectively, whereas nocodazole, a positive control, has shown lower antitubulin activity with an IC50 value of 2.64 μM. Furthermore, these compounds induced apoptosis by loss of mitochondrial membrane potential, propidium iodide (PI) staining and the activation of caspase-3. Results of a fluorescence based competitive colchicine binding assay suggest that these conjugates bind successfully at the colchicine binding site of tubulin. These investigations reveal that such conjugates containing pyrazole with a trimethoxy phenyl ring and indole moieties have potential for the development of newer chemotherapeutic agents. more...

The present study illustrates the optimization and characterization of β-glucosidase from a bacterial isolate, strain SG9. Sixty-eight different variables were first screened by one factor at a time method. The screened variable optimization was then performed by Plackett-Burman design followed by Box-Behnken response surface methodology. Thirty-one variables were screened, of which five variables were found to be significant. Box-Behnken design was then performed using the most significant variables, viz., esculin, K2HPO4 and MgSO4. The maximum enzyme activity was observed with an optimal medium composition of esculin (1.9 g/L), K2HPO4 (0. 5 g/L) and MgSO4 (0.3 g/L) with a predicted value of 3392.01 IU. The maximum β-glucosidase production achieved was 3340 IU. The bacterial strain was identified by 16S rRNA gene sequence and biochemical characterization. The strain was identified as Bacillus stratosphericus and is a first report of its kind. more...

Prescription opioid abuse is a global crisis. New treatment strategies for pain and opioid use disorders are urgently required. We evaluated the effects of R-VK4-40, a highly selective dopamine (DA) D3 receptor (D3R) antagonist, on the rewarding and analgesic effects of oxycodone, the most commonly abused prescription opioid, in rats and mice. Systemic administration of R-VK4-40 dose-dependently inhibited oxycodone self-administration and shifted oxycodone dose-response curves downward in rats. Pretreatment with R-VK4-40 also dose-dependently lowered break-points for oxycodone under a progressive-ratio schedule. To determine whether a DA-dependent mechanism underlies the impact of D3 antagonism in reducing opioid reward, we used optogenetic approaches to examine intracranial self-stimulation (ICSS) maintained by optical activation of ventral tegmental area (VTA) DA neurons in DAT-Cre mice. Photoactivation of VTA DA in non-drug treated mice produced robust ICSS behavior. Lower doses of oxycodone enhanced, while higher doses inhibited, optical ICSS. Pretreatment with R-VK4-40 blocked oxycodone-enhanced brain-stimulation reward. By itself, R-VK4-40 produced a modest dose-dependent reduction in optical ICSS. Pretreatment with R-VK4-40 did not compromise the antinociceptive effects of oxycodone in rats, and R-VK4-40 alone produced mild antinociceptive effects without altering open-field locomotion or rotarod locomotor performance. Together, these findings suggest R-VK4-40 may permit a lower dose of prescription opioids for pain management, potentially mitigating tolerance and dependence, while diminishing reward potency. Hence, development of R-VK4-40 as a therapy for the treatment of opioid use disorders and/or pain is currently underway. This article is part of the Special Issue entitled 'New Vistas in Opioid Pharmacology'. more...

A series of new imidazo[2,1-b][1,3,4]thiadiazole–chalcones were synthesized by Claisen–Schmidt condensation and evaluated for their cytotoxic activity against various human cancer cell lines. These compounds showed moderate to appreciable antiproliferative activities. Interestingly, compounds like 11a and 11b exhibited significant cytotoxic activity with IC50 values ranging from 0.65 to 2.25 μM in certain cancer cell lines. The structure–activity relationship (SAR) studies reveal that 3,4,5-trimethoxy group containing compounds showed superior cytotoxic activity against selected cancer cell lines compared to other chalcones. These compounds showed G0/G1 phase arrest, apart from activation of caspase-3 and 8 in DU-145 cells. The growth inhibitory effect of these compounds was associated with a decrease in cell cycle regulatory protein cyclin D1 and increase in cyclin dependent kinase inhibitors like Cip1/p21 and Kip1/p27. more...

A simple, greener and highly efficient method for the synthesis of functionalized quinoxalines has been developed employing L-proline as a catalyst in water. To the best of our knowledge this transformation is achieved for the first time using an organic catalyst. A small library of quinoxaline–sulphonamide conjugates have been synthesized using this protocol. The newly synthesized conjugates have been tested for their cytotoxicity and antimicrobial activity against several bacterial strains including one fungal strain. The majority of the compounds have exhibited significant cytotoxicity as well as antimicrobial activity. Compounds 5a, 5b and 5d were found to be promising with respect to both cytotoxicity and antimicrobial activity. more...

A library of 2,5-disubstituted 1,3,4-oxadiazole derivatives of (E)-2-aryl-5-(3,4,5-trimethoxystyryl)-1,3,4-oxadiazoles 4(a–o) and (E)-2-aryl-5-(2-benzo[d][1,3]dioxol-5-yl)vinyl)-1,3,4-oxadiazoles 5(a–q) were synthesized and evaluated for their in vitro acetylcholinesterase (AChE) inhibitory activity. All the synthesized compounds exhibited moderate to good inhibitory activity toward the AChE enzyme. Among the oxadiazole derivatives examined, compounds 4a, 4g, 5c, and 5m (IC50 values of 24.89, 13.72, 37.65, and 19.63 μM, respectively) were found to be promising inhibitors of AChE. Molecular protein–ligand docking studies were examined for these compounds using GOLD docking software and their binding conformations were determined and the simultaneous interactions mode was also established for the potent derivatives. more...

A number of linezolid-like oxazolidino-sulfonamides (7a–y and 8a–b) were designed and synthesized with a view to develop antimicrobial agents with improved properties. Most of the synthesized compounds showed good to moderate activity against a panel of standard Gram-positive and Gram-negative bacteria and fungal strains. The compounds 7i and 7v exhibited significant activity, with a MIC value of 2.0–6.0 μg/mL against a panel of Gram-positive and Gram-negative bacteria. These compounds also showed activity against Candida albicans, with a MIC value of 4.0 μg/mL. A correlation of the antimicrobial activity with calculated lipophilicity values (C log P) is also presented. more...

Cancer has been established as the "Emperor of all maladies". In recent years, medicinal chemistry has focused on identifying novel anti-cancer compounds; though discovery of these compounds appears to be a herculean task. In present study, we synthesized forty pyrazolochalcone conjugates and explored their cytotoxic activity against a panel of sixty cancer cell lines. Fifteen conjugates of the series showed excellent growth inhibition (13b-e, 13h-j, 14c-d, 15 a, 15 c-d, 16b, 16d and 18f; GI50 for MCF-7: 0.4-20 μM). Conjugates 13b, 13c, 13d, 16b and 14d were also evaluated for their cytotoxic activity in human breast cancer cell line (MCF-7). The promising candidates induced cell cycle arrest, mitochondrial membrane depolarization and apoptosis in MCF-7 cells at a 2 μM concentration. Furthermore, inhibition of PI3K/Akt/mTOR pathway-regulators such as PI3K, p-PI3K, p-AKT, and mTOR were observed; as well as upregulation of p-GSK3β and tumor-suppressor protein, PTEN. Our study indicates that pyrazolochalcone conjugates could serve as potential leads in the development of tailored cancer therapeutics. more...

Aiming to develop a new target for the anticancer treatment, a series of 5'H-spiro[indoline-3,4'-pyrrolo [1,2-a]quinoxalin]-2-ones has been synthesized by simple, highly efficient and environmentally friendly method in excellent yields under catalyst-free conditions using ethanol as a green solvent. A simple filtration of the reaction mixture and subsequent drying affords analytically pure products. The synthesized derivatives were evaluated for their antiproliferative activity against five different human cancer cell lines, among the congeners compound 3n showed significant cytotoxicity against the human prostate cancer (DU-145). Flow cytometric analysis revealed that this compound induces cell cycle arrest in the G0/G1 phase and Western blot analysis suggested that reduction in Cdk4 expression level leads to apoptotic cell death. This was further confirmed by mitochondrial membrane potential ((ΔΨm), Annexin V-FITC assay and docking experiments. Furthermore, it was observed that there is an increase in expression levels of cyclin dependent kinase inhibitors like Cip1/p21 and Kip1/p27. more...

In an ongoing survey of the bioactive potential of microorganisms from Ladakh, India, the culture medium of a bacterial strain of a new Pseudomonas sp., strain ICTB-745, isolated from an alkaline soil sample collected from Leh, Ladakh, India, was found to contain metabolites that exhibited broad-spectrum antimicrobial and biosurfactant activities. Bioactivity-guided purification resulted in the isolation of four bioactive compounds. Their chemical structures were elucidated by (1)H and (13)C NMR, 2D-NMR (HMBC, HSQC, (1)H,(1)H-COSY, and DEPT- 135), FT-IR, and mass spectroscopic methods, and were identified as 1-hydroxyphenazine, phenazine-1-carboxylic acid (PCA), rhamnolipid-1 (RL-1), and rhamnolipid-2 (RL-2). These metabolites exhibited various biological activities like antimicrobial and efficient cytotoxic potencies against different human tumor cell lines such as HeLa, HepG2, A549, and MDA MB 231. RL-1 and RL-2 exhibited a dose-dependent antifeedant activity against Spodoptera litura, producing about 82.06% and 73.66% antifeedant activity, whereas PCA showed a moderate antifeedant activity (63.67%) at 60 microgram/cm2 area of castor leaf. Furthermore, PCA, RL-1, and RL-2 exhibited about 65%, 52%, and 47% mortality, respectively, against Rhyzopertha dominica at 20 microgram/ml. This is the first report of rhamnolipids as antifeedant metabolites against Spodoptera litura and as insecticidal metabolites against Rhyzopertha dominica. The metabolites from Pseudomonas sp. strain ICTB-745 have interesting potential for use as a biopesticide in pest control programs. more...

Selective high-affinity antagonists for the dopamine D3 receptor (D3R) are sought for treating substance use disorders. Positron emission tomography (PET) with an effective D3R radioligand could be a useful tool for the development of such therapeutics by elucidating pharmacological specificity and target engagement in vivo. Currently, a D3R-selective radioligand does not exist. The D3R ligand, N-(4-(4-(3-chloro-2-methoxyphenyl)piperazin-1-yl)butyl)-1H-indole-2-carboxamide (BAK4-51, 1), has attractive properties for PET radioligand development, including full antagonist activity, very high D3R affinity, D3R selectivity, and moderate lipophilicity. We labeled 1 with the positron-emitter carbon-11 (t1/2 = 20.4 min) in the methoxy group for evaluation as a radioligand in animals with PET. However, [11C]1 was found to be an avid substrate for brain efflux transporters and lacked D3R-specific signal in rodent and monkey brain in vivo. more...

A series of phenstatin/isocombretastatin-oxindole conjugates was synthesized and tested for their cytotoxic activity against five human cancer cells such as prostate (DU-145), lung (A549), colon (HT-29), breast (MCF-7), liver (HepG2) cancer cells with IC50 values ranging from 0.049 to 38.90 μM. Amongst them, two conjugates (5c and 5d) showed broad spectrum of antiproliferative efficacy on lung cancer cells with an IC50 value of 79 nM and 93 nM, respectively, whereas on colon cancer cells with an IC50 values 45 nM and 49 nM, respectively. In addition, cell cycle assay revealed that these conjugates (5c and 5d) arrest at the G2/M phase and leads to apoptotic cell death which was confirmed by Annexin V-FITC and mitochondrial membrane depolarization. Further, the tubulin polymerization assay analysis results suggest that these conjugates particularly 5c and 5d exhibit significant inhibitory effect on the tubulin assembly with an IC50 value of 1.23 μM and 1.01 μM, respectively. Molecular docking studies indicated that these compounds (5c and 5d) occupy the colchicine binding site of the tubulin. more...

As pyrazole and isoxazole based derivatives are well-known for displaying a considerable biological profile, an attempt has been made to unravel their cytotoxic potential. In this context, a number of pyrazole/isoxazole linked arylcinnamide conjugates (15a–o and 21a–n) have been synthesized by employing a straight forward route. The basic structure comprised three ring scaffolds (A, B and C): methoxyphenyl rings as A and C rings and a five membered heterocyclic ring (pyrazole or isoxazole) as the B-ring. To achieve clear understanding, these derivatives are categorized as pyrazole-phenylcinnamides (PP) and isoxazole-phenylcinnamides (IP). These compounds have been evaluated for their ability to inhibit the growth of various human cancer cell lines such as HeLa, DU-145, A549 and MDA-MB231 and most of them exhibit considerable cytotoxic effects. Some of them like 15a, 15b, 15e, 15i and 15l exhibit promising cytotoxicity in HeLa cells (IC50 = 0.4, 1.8, 1.2, 2.7 and 1.7 μM). Amongst them 15a, 15b and 15e were taken up for detailed biological studies, they were found to arrest the cells in the G2/M phase of the cell cycle. Moreover, they were investigated for their effect on the microtubular cytoskeletal system by using a tubulin polymerization assay, immunofluroscence and molecular docking studies; interestingly they demonstrate a significant inhibition of tubulin polymerization. more...

Quinoxaline (Vd) is further transformed via reduction of the nitro group and sulfonylation of the resulting amine yielding arylsulfonamides, e.

A series of phenstatin/isocombretastatin–chalcones were synthesized and screened for their cytotoxic activity against various human cancer cell lines. Some representative compounds exhibited significant antiproliferative activity against a panel of sixty human cancer cell lines of the NCI, with GI50 values in the range of 0.11 to 19.0 μM. Three compounds (3b, 3c and 3e) showed a broad spectrum of antiproliferative efficacy on most of the cell lines in the sub-micromolar range. In addition, all the synthesized compounds (3a–l and 4a–l) displayed moderate to excellent cytotoxicity against breast cancer cells such as MCF-7 and MDA-MB-231 with IC50 values in the range of 0.5 to 19.9 μM. Moreover, the tubulin polymerization assay and immunofluorescence analysis results suggest that some of these compounds like 3c and 3e exhibited significant inhibitory effect on the tubulin assembly with an IC50 value of 0.8 μM and 0.6 μM respectively. A competitive binding assay suggested that these compounds bind at the colchicine-binding site of tubulin. A cell cycle assay revealed that these compounds arrest at the G2/M phase and lead to apoptotic cell death. Furthermore, this was confirmed by Hoechst 33258 staining, activation of caspase 9, DNA fragmentation, Annexin V-FITC and mitochondrial membrane depolarization. Molecular docking studies indicated that compounds like 3e occupy the colchicine binding site of tubulin. more...

A series of novel pyrano[3,2-c]carbazole derivatives have been synthesized by a simple one-pot, three component reaction of aromatic aldehydes, malononitrile–ethyl cyanoacetate and 4-hydroxycarbazoles catalyzed by triethylamine. The antiproliferative activity of the derivatives on various cancer cell lines such as MDA-MB-231, K562, A549 and HeLa was investigated. Among 9a–p, congeners 9a, 9c, 9g and 9i showed profound antiproliferative activity with IC50 values ranging from 0.43 to 8.05 μM and induced apoptosis significantly by inhibiting tubulin polymerization. Cell-based biological assays demonstrated that treatment of cell lines with compounds 9a, 9c, 9g and 9i results in G2/M phase arrest of the cell cycle. Moreover the derivatives significantly disrupted the microtubule network, produced an elevation of cyclinB1 protein levels and induced apoptosis by increasing the caspase-3 levels. In particular, 9i strongly inhibited tubulin assembly compared to the positive control CA-4. Molecular docking studies demonstrated that all the lead compounds selectively occupy the colchicine binding site of the tubulin polymer. more...

In an attempt to develop potent and selective anticancer agents, a series of twenty arylpyrazole linked benzimidazole conjugates (10a-t) were designed and synthesized as microtubule destabilizing agents. The joining of arylpyrazole to the benzimidazole moiety resulted in a four ring (A, B, C and D) molecular scaffold that comprises of polar heterocyclic rings in the middle associated with rotatable single bonds and substituted aryl rings placed in the opposite directions. These conjugates were evaluated for their ability to inhibit the growth of sixty cancer cell line panel of the NCI. Among these some conjugates like 10a, 10b, 10d, 10e, 10p and 10r exhibited significant growth inhibitory activity against most of the cell lines ranging from 0.3 to 13μM. Interestingly, the conjugate 10b with methoxy group on D-ring expressed appreciable cytotoxic potential. A549 cells treated with some of the potent conjugates like 10a, 10b and 10d arrested cells at G2/M phase apart from activating cyclin-B1 protein levels and disrupting microtubule network. Moreover, these conjugates effectively inhibited tubulin polymerization with IC50 values of 1.3-3.8μM. Whereas, the caspase assay revealed that they activate the casepase-3 leading to apoptosis. Particularly 10b having methoxy substituent induced activity almost 3 folds higher than CA-4. Furthermore, a competitive colchicine binding assay and molecular modeling analysis suggests that these conjugates bind to the tubulin successfully at the colchicine binding site. These investigations reveal that such conjugates having pyrazole and benzimidazole moieties have the potential in the development of newer chemotherapeutic agents. more...

A number of pyrazole-oxadiazole conjugates were synthesized and evaluated for their ability to function as antiproliferative agents on various human cancer cell lines. These conjugates are comprised of pyrazole and oxadiazole scaffolds closely attached to each other without any spacer as two structural classes. The Type I class has a trimethoxy substituent and the type II class has a 3,4-(methylenedioxy) substituent on their A rings. Among these conjugates 11a, 11d and 11f manifest potent cytotoxicity with IC50 values ranging from 1.5 μM to 11.2 μM and inhibit tubulin polymerization with IC50 values of 1.3 μM, 3.9 μM and 2.4 μM respectively. The cell cycle assay showed that treatment with these conjugates results in accumulation of cells in the G2/M phase and disrupts the microtubule network. Elucidation of zebrafish embryos revealed that the conjugates cause developmental defects. Molecular docking simulations determined the binding modes of these potent conjugates at the colchicine site of tubulin. more...

A series of aminostilbene-arylpropenones were designed and synthesized by Michael addition and were investigated for their cytotoxic activity against various human cancer cell lines. Some of the investigated compounds exhibited significant antiproliferative activity against a panel of 60 human cancer cell lines of the US National Cancer Institute, with 50 % growth inhibition (GI50) values in the range from < 0.01 to 19.9 μM. One of the compounds showed a broad spectrum of antiproliferative efficacy on most of the cell lines, with a GI50 value of < 0.01 μM. All of the synthesized compounds displayed cytotoxicity against A549 (non-small-cell lung cancer), HeLa (cervical carcinoma), MCF-7 (breast cancer), and HCT116 (colon carcinoma) with 50 % inhibitory concentration (IC50) values ranging from 0.011 to 8.56 μM. A cell cycle assay revealed that these compounds arrested the G2/M phase of the cell cycle. Two compounds exhibited strong inhibitory effects on tubulin assembly with IC50 values of 0.71 and 0.79 μM. Moreover, dot-blot analysis of cyclin B1 demonstrated that some of the congeners strongly induced cyclin B1 protein levels. Molecular docking studies indicated that these compounds occupy the colchicine binding site of tubulin. more...

A series of β-carboline–benzimidazole conjugates bearing a substituted benzimidazole and an aryl ring at C3 and C1 respectively were designed and synthesized. The key step of their preparation was determined to involve condensation of substituted o-phenylenediamines with 1-(substituted phenyl)-9H-pyrido[3,4-b]indole-3-carbaldehyde using La(NO3)3·6H2O as a catalyst and their cytotoxic potential was evaluated. Conjugates 5a, 5d, 5h and 5r showed enhanced cytotoxic activity (GI50 values range from 0.3 to 7.1 μM in most of the human cancer cell lines) in comparison to some of the previously reported β-carboline derivatives. To substantiate the cytotoxic activity and to understand the nature of interaction of these conjugates with DNA, spectroscopy, DNA photocleavage and DNA topoisomerase I inhibition (topo-I) studies were performed. These conjugates (5a, 5d and 5r) effectively cleave pBR322 plasmid DNA in the presence of UV light. In addition, the effect of these conjugates on DNA Topo I inhibition was studied. The mode of binding of these new conjugates with DNA was also examined by using both biophysical as well as molecular docking studies, which supported their multiple modes of interaction with DNA. Moreover, an in silico study of these β-carboline–benzimidazole conjugates reveals that they possess drug-like properties. more...

A library of imidazopyridine-oxindole conjugates was synthesised and investigated for anticancer activity against various human cancer cell lines. Some of the tested compounds, such as 10 a, 10 e, 10 f, and 10 k, exhibited promising antiproliferative activity with GI50 values ranging from 0.17 to 9.31 μM. Flow cytometric analysis showed that MCF-7 cells treated by these compounds arrested in the G2 /M phase of the cell cycle in a concentration-dependent manner. More particularly, compound 10 f displayed a remarkable inhibitory effect on tubulin polymerisation. All the compounds depolarised mitochondrial membrane potential and caused apoptosis. These results are further supported by the decreased phosphorylation of Akt at Ser473. Studies on embryonic development revealed that the lead compounds 10 f and 10 k caused delay in the development of zebra fish embryos. Docking of compound 10 f with tubulin protein suggested that the imidazo[1,2-a]pyridine moiety occupies the colchicine binding site of tubulin. more...

In an effort to discover new anti-tubercular agents, a series of new diarylpyrrole–oxazolidinone conjugates have been designed and synthesized. The anti-tubercular activity of these new conjugates ( 4a – n and 5a – d ) against Mycobacterium tuberculosis H 37 Rv and drug resistance strains such as M. tuberculosis Rif R and M. tuberculosis XDR are discussed, wherein compound 4i has been found to be the most potent amongst the series. MTT assay was performed on the active conjugates of the series ( 4b – f , 4i and 5c ) against mouse macrophage (J-774) cells to evaluate cytotoxic effects and selective index values. In addition, these conjugates ( 4a – n and 5a – d ) are also tested against a panel of Gram-positive and Gram-negative bacterial strains. The docking studies have been carried out to provide some insight into the mechanism of action for this class of compounds. more...