Preventive effects of fructose and N‐acetyl‐L‐cysteine against cytotoxicity induced by the psychoactive compounds N‐methyl‐5‐(2‐aminopropyl)benzofuran and 3,4‐methylenedioxy‐N‐methamphetamine in isolated rat hepatocytes

Psychoactive compounds, N‐methyl‐5‐(2‐aminopropyl)benzofuran (5‐MAPB) and 3,4‐methylenedioxy‐N‐methamphetamine (MDMA), are known to be hepatotoxic in humans and/or experimental animals. As previous studies suggested that these compounds elicited cytotoxicity via mitochondrial dysfunction and/or oxidative stress in rat hepatocytes, the protective effects of fructose and N‐acetyl‐l ‐cysteine (NAC) on 5‐MAPB‐ and MDMA‐induced toxicity were studied in rat hepatocytes. These drugs caused not only concentration‐dependent (0–4 mm ) and time‐dependent (0–3 hours) cell death accompanied by the depletion of cellular levels of adenosine triphosphate (ATP) and glutathione (reduced form; GSH) but also an increase in the oxidized form of GSH. The toxic effects of 5‐MAPB were greater than those of MDMA. Pretreatment of hepatocytes with either fructose at a concentration of 10 mm or NAC at a concentration of 2.5 mm prevented 5‐MAPB?/MDMA‐induced cytotoxicity. In addition, the exposure of hepatocytes to 5‐MAPB/MDMA caused the loss of mitochondrial membrane potential, although the preventive effect of fructose was weaker than that of NAC. These results suggest that: (1) 5‐MAPB?/MDMA‐induced cytotoxicity is linked to mitochondrial failure and depletion of cellular GSH; (2) insufficient cellular ATP levels derived from mitochondrial dysfunction were ameliorated, at least in part, by the addition of fructose; and (3) GSH loss via oxidative stress was prevented by NAC. Taken collectively, these results indicate that the onset of toxic effects caused by 5‐MAPB/MDMA may be partially attributable to cellular energy stress as well as oxidative stress.     

Identification of five substituted phenethylamine derivatives 5‐MAPDB, 5‐AEDB,MDMA methylene homolog, 6‐Br‐MDMA,and 5‐APB‐NBOMe

This paper reports analytical properties of five substituted phenethylamine derivatives seized from a clandestine laboratory. These five derivatives include 5‐(2‐methylaminopropyl)‐2,3‐dihydrobenzofuran (5‐MAPDB, 1 ), 5‐(2‐aminoethyl)‐2,3‐dihydrobenzofuran (5‐AEDB, 2 ), N ,2‐dimethyl‐3‐(3,4‐methylenedioxyphenyl)propan‐1‐amine (MDMA methylene homolog, 3 ), 6‐bromo‐3,4‐methylenedioxymethamphetamine (6‐Br‐MDMA, 4 ), and 1‐(benzofuran‐5‐yl)‐N ‐(2‐methoxybenzyl)propan‐2‐amine (5‐APB‐NBOMe, 5 ). These compounds were identified by liquid chromatography‐quadrupole time‐of‐flight mass spectrometry (LC‐QTOF‐MS), gas chromatography‐mass spectrometry (GC‐MS), and nuclear magnetic resonance spectroscopy (NMR). No analytical properties about compounds 1‐4 have appeared until now, making this the first report on these compounds. Copyright © 2016 John Wiley & Sons, Ltd.     

Analytical characterization of four new ortho‐methoxybenzylated amphetamine‐type designer drugs

In a seizure of German custom authorities four N‐(ortho‐methoxybenzyl)amines with amphetamine partial structure were obtained as pure compounds: N‐(ortho‐methoxybenzyl)‐3,4‐dimethoxyamphetamine (3,4‐DMA‐NBOMe ( 1 )), N‐(ortho‐methoxybenzyl)‐4‐ethylamphetamine (4‐EA‐NBOMe ( 2 )), N‐(ortho‐methoxybenzyl)‐4‐methylmethamphetamine (4‐MMA‐NBOMe ( 3 )), and N‐(ortho‐methoxybenzyl)‐5‐(2‐aminopropyl)benzofuran (5‐APB‐NBOMe ( 4 )). The compounds have been detected in Germany for the first time and no analytical data had been previously published. Mass spectrometric (MS), infrared (IR) spectroscopic, and nuclear magnetic resonance (NMR) spectroscopic data are presented. Copyright © 2015 John Wiley & Sons, Ltd.     

Identification of (2‐aminopropyl)benzofuran (APB) phenyl ring positional isomers in Internet purchased products

5‐(2‐Aminopropyl)benzofuran (5‐APB), a ‘research chemical’ that was first reported by UK authorities to the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) in 2010, is anecdotally reported to produce a combination of stimulant and entactogenic effects. More recently, in 2011, 6‐(2‐aminopropyl)benzofuran (6‐APB) was identified by Hungarian authorities. To confirm positional isomer identity in Internet purchased products, 4‐ 5‐ 6‐ and 7‐APBs were synthesized and found to be separable by gas chromatography (as heptafluorobutyramide derivatives) and liquid chromatography. The analyses of products purchased from online vendors of ‘research chemicals’ identified the presence of 5‐ or 6‐APBs. These findings were further confirmed by liquid chromatography‐mass spectrometry and ¹H nuclear magnetic resonance spectroscopy. In products containing 6‐APB, the 4‐ positional isomer was also identified and this may have arisen during the manufacturing process. Copyright © 2013 John Wiley & Sons, Ltd.     

Cytotoxic effects of 3,4-methylenedioxy-<Emphasis Type="Italic">N</Emphasis>-alkylamphetamines,MDMA and its analogues,on isolated rat hepatocytes

The amphetamine-derived designer drugs have been illegally used worldwide as recreational drugs, some of which are known to be hepatotoxic in humans. To compare their cytotoxic effects, 3,4-methylenedioxy-N-methamphetamine (MDMA) and its related analogues, N-methyl-1-(3,4-methylenedioxyphenyl)-2-butanamine (MBDB), 3,4-(methylenedioxyphenyl)-2-butanamine (BDB) and 2-methylamino-1-(3,4-methylenedioxyphenyl)-propane-1-one (methylone) were studied in freshly isolated rat hepatocytes. MBDB caused not only concentration (0–4.0 mM)- and time (0–2 h)-dependent cell death accompanied by the formation of cell blebs, and the loss of cellular ATP and adenine nucleotide pools, and reduced glutathione levels, but also the accumulation of oxidized glutathione. Of the other analogues examined, the cytotoxicity of MBDB and BDB was greater than that of MDMA and methylone, suggesting that hepatotoxicity is generally induced by these drugs. In addition, DNA damage and the induction of reactive oxygen species were greater after the incubation of hepatocytes with MBDB (2 and 4 mM) than after that with MDMA. In isolated liver mitochondria, MBDB/BDB resulted in a greater increase in the rate of state 4 oxygen consumption than did MDMA/methylone, indicating an uncoupling effect and a decrease in the rate of state 3 oxygen consumption in a concentration dependent manner. Furthermore, MBDB resulted in mitochondrial swelling dependent on the mitochondrial permeability transition (MPT); the effect of MDMA was less than that of MBDB. Taken collectively, these results suggest that (1) the onset of cytotoxicity caused by designer drugs such as MBDB and MDMA is linked to mitochondrial failure dependent upon the induction of the MPT accompanied by mitochondrial depolarization and depletion of ATP through uncoupling of oxidative phosphorylation in rat hepatocytes, and (2) MBDB and MDMA elicit DNA damage, suggesting that nuclei as well as mitochondria are target sites of these compounds.     

Combination effects of amphetamines under hyperthermia ‐ the role played by oxidative stress

Rise in body temperature is a life‐threatening consequence of 3,4‐methylenedioxymethamphetamine (MDMA, ecstasy) abuse. We evaluated the impact of hyperthermia on the cytotoxicity of combinations of MDMA and three other amphetamines, often co‐ingested. For this, Hep G2 cells were exposed to MDMA, d ‐amphetamine, methamphetamine and 4‐methylthioamphetamine, individually or combined, at 40.5 °C. The results were compared with normothermia data (37.0 °C). Mixture additivity expectations were calculated by independent action and concentration addition (CA) models. To delineate the mechanism(s) underlying the elicited effects, a range of stress endpoints was evaluated, including quantification of reactive oxygen/nitrogen species (ROS/RNS), lipid peroxidation, reduced/oxidized glutathione (GSH/GSSG), ATP and mitochondrial membrane potential (Δψm) changes. Our data show that, in hyperthermia, amphetamines acted additively and mixture effects were accurately predicted by CA. At 40.5 °C, even slight increases in the concentrations of each drug/mixture promoted significant rises in cytotoxicity, which quickly shifted from roughly undetectable to maximal mortality. Additionally, the increase of RNS/ROS production, decrease of GSH, ATP depletion and mitochondrial impairment were exacerbated under hyperthermia. Importantly, when equieffective cytotoxic concentrations of the mixture and individual amphetamines were compared for all tested stress endpoints, mixture effects did not deviate from those elicited by individual treatments, suggesting that these amphetamines have a similar mode of action, which is not altered in combination. Concluding, our data indicate that amphetamine mixtures produce deleterious effects, even when individual drugs are combined at negligible concentrations. These effects are strongly exacerbated in hyperthermia, emphasizing the potential increased risks of ecstasy intake, especially when hyperthermia occurs concurrently with polydrug abuse. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis,In Vitro Cytotoxicity and Radiosensitizing Activity of Novel 3‐[(2,4‐Dinitrophenylamino)Alkyl] Derivatives of 5‐Fluorouracil

Previously, it was reported that 3[3‐(2,4‐dinitrophenylamino)‐propyl]‐5‐fluorouracil 8c unlike its components 5‐fluorouracil (5‐FU) 6 and 2,4‐dinitroaniline 2 in HT‐29 cells under aerobic conditions had no cytotoxicity but showed radiosensitizing activity. In this study several analogues of 8c differing in the number of linking methylene groups were prepared and tested for in vitro cytotoxicity and radiosensitizing activity under both aerobic and hypoxic conditions. Tethered compound 8a was prepared in one pot by the reaction of 5‐FU 6 with paraformaldehyde and 2,4‐dinitroaniline 2 in the presence of the concentrated hydrochloric acid, and compounds 8b–f were prepared by the reaction of N‐(bromoalkyl) ‐ 2,4‐dinitrobenzeneamines 5b–f with 1‐(t‐butoxycarbonyl)‐5‐fluorouracil 7 followed by hydrolysis of the protecting group. The cytotoxicity of the tested compounds were measured by 3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT), and propidium iodide (PI)‐digitonin assays and values of sensitization enhancement ratio (SER) as a measure of the radiosensitizing activity were measured from radiation survival curves in the absence and presence of each sensitizer for 37% survival respectively. Results showed that tethered compounds 8a–f induced time‐ and concentration‐dependent cytotoxicity under hypoxia but had no significant effect under aerobic conditions. These compounds also showed selective and concentration‐dependent radiocytotoxicity under hypoxic conditions.     

Carbon‐14 radiosynthesis of the benzofuran derivative and β‐amyloid plaque neuroimaging positron emission tomography radioligand AZD4694

In support of a metabolite study, the β‐amyloid plaque neuroimaging positron‐emission tomography radioligand AZD4694 was labeled with carbon‐14 in 10 radiosynthetic steps starting from radiolabeled carbon dioxide. [¹⁴C]AZD4694 was labeled in the benzofuran heterocycle with a specific activity of 2.1 GBq/mmol and with a radiochemical purity of >99%. The described synthesis constitutes a general method to carbon‐14‐labeled substituted benzofurans.     

Syntheses and analytical characterizations of novel (2‐aminopropyl)benzo[b]thiophene (APBT) based stimulants

Two groups of amphetamine‐like drugs with psychostimulant properties that were first developed during the course of scientific studies and later emerged as new psychoactive substances (NPS) are based on the (2‐aminopropyl)indole (API) and (2‐aminopropyl)benzofuran (APB) structural scaffolds. However, sulfur‐based analogs with a benzo[b]thiophene structure (resulting in (2‐aminopropyl)benzo[b]thiophene (APBT) derivatives) have received little attention. In the present investigation, all six racemic APBT positional isomers were synthesized in an effort to understand their structure–activity relationships relative to API‐ and APB‐based drugs. One lesson learned from the NPS phenomenon is that one cannot exclude the appearance of such substances on the market. Therefore, an in‐depth analytical characterization was performed, including various single‐ and tandem mass spectrometry (MS) and ionization platforms coupled to gas chromatography (GC) and liquid chromatography (LC), nuclear magnetic resonance spectroscopy (NMR), and solid phase and GC condensed phase infrared spectroscopy (GC‐sIR). Various derivatizations have also been explored; it was found that all six APBT isomers could be differentiated during GC analysis after derivatization with heptafluorobutyric anhydride and ethyl chloroformate (or heptafluorobutyric anhydride and acetic anhydride) under non‐routine conditions. Discriminating analytical features can also be derived from NMR, GC‐EI/CI‐ single‐ and tandem mass spectrometry, LC (pentafluorophenyl stationary phase), and various infrared spectroscopy approaches (including GC‐sIR). Availability of detailed analytical data obtained from these novel APBT‐type stimulants may be useful to researchers and scientists in cases where forensic and clinical investigations are warranted.     

3‐butyl‐6‐fluoro‐1(3H)‐isobenzofuranone (6‐F‐NBP), a derivative of dl‐n‐butylphthalide,inhibits glutamate‐induced cytotoxicity in PC12 cells

It is widely recognized that glutamate (Glu)‐induced cytotoxicity, intracellular calcium overload and the excessive free radical production are key events in the development and progression of ischemic brain injury. dl‐3‐n‐butylphthalide (NBP), an anti‐ischemic agent, has therapeutic effects in animal models of vascular dementia. The aim of the present study was to investigate the protective effect of 3‐butyl‐6‐fluoro‐1(3H)‐isobenzofuranone (6‐F‐NBP), a derivative of NBP on Glu‐induced cytotoxicity in rat pheochromocytoma (PC12) cells, and to compare this action with NBP. The results showed that after 24‐h incubation with Glu (5 mM), cell viability and mitochondrial membrane potential (MMP) were decreased. In contrast, the content of reactive oxygen species (ROS), activity of nitric oxide synthase (NOS), and apoptosis rate, as well as intracellular accumulation of [Ca²⁺]_i, were increased, 6‐F‐NBP inhibited the damage induced by Glu in a dose‐dependent manner and exerted a more potent effect than NBP, indicating that 6‐F‐NBP exhibited a protective effect against Glu‐induced cytotoxicity in cultured PC12 cells. Drug Dev Res 73: 11–17, 2012. © 2011 Wiley Periodicals, Inc.     

5‐Fluorouracil combined with apigenin enhances anticancer activity through mitochondrial membrane potential (ΔΨm)‐mediated apoptosis in hepatocellular carcinoma

The development of chemoresistance may reduce the efficacy of chemotherapeutic drugs for treating hepatocellular carcinoma (HCC). In the present study, the effects of apigenin on intensifying the chemosensitivity of HCC cells and an HCC xenograft model in response to 5‐fluorouracil (5‐FU) were investigated. Sub‐toxic concentrations of apigenin (4 μmol/L) significantly enhanced the cytotoxicity of 5‐FU (100 μg/mL) in HCC cells. In vivo, combined treatment with apigenin (20 mg/kg, five times/week for 3 weeks) and 5‐FU (20 mg/kg for 5 consecutive days) significantly inhibited the growth of HCC xenograft tumours. Annexin V–propidium iodide dual staining assays, terminal deoxyribonucleotidyl transferase‐mediated dUTP–digoxigenin nick end‐labelling assays and western blotting analysis were used to confirm the synergistic effects of apigenin and 5‐FU on HCC apoptosis. Coincubation of HCC cells with apigenin and 5‐FU increased levels of reactive oxygen species (ROS), which was followed by a decrease in the mitochondrial membrane potential (ΔΨm). In addition, combined triggered the mitochondrial apoptotic pathway, as indicated by decreased Bcl‐2 expression and loss of ΔΨm, with significant activation of caspase 3 and poly(ADP‐ribose) polymerase. The present study is the first to demonstrate that apigenin may potentiate the cytotoxicity of 5‐FU in HCC via inhibition of ROS‐mediated drug resistance and concurrent activation of the mitochondrial pathways of apoptosis.     

Mitochondrial and liver oxidative stress alterations induced by N‐butyl‐N‐(4‐hydroxybutyl)nitrosamine: relevance for hepatotoxicity

The most significant toxicological effect of nitrosamines like N‐butyl‐N‐(4‐hydroxybutyl)nitrosamine (BBN) is their carcinogenic activity, which may result from exposure to a single large dose or from chronic exposure to relatively small doses. However, its effects on mitochondrial liver bioenergetics were never investigated. Liver is the principal organ responsible for BBN metabolic activation, and mitochondria have a central function in cellular energy production, participating in multiple metabolic pathways. Therefore any negative effect on mitochondrial function may affect cell viability. In the present work, ICR male mice were given 0.05% of BBN in drinking water for a period of 12 weeks and were sacrificed one week later. Mitochondrial physiology was characterized in BBN‐ and control‐treated mice. Transmembrane electric potential developed by mitochondria was significantly affected when pyruvate–malate was used, with an increase in state 4 respiration observed for pyruvate–malate (46%) and succinate (38%). A decrease in the contents of one subunit of mitochondrial complex I and in one subunit of mitochondrial complex IV was also observed. In addition, the activity of both complexes I and II was also decreased by BBN treatment. The treatment with BBN increases the susceptibility of liver mitochondria to the opening of the mitochondrial permeability transition pore. This susceptibility could be related with the increase in the production of H₂O₂ by mitochondria and increased oxidative stress confirmed by augmented susceptibility to lipid peroxidation. These results lead to the conclusion that hepatic mitochondria are one primary target for BBN toxic action during liver metabolism. Copyright © 2011 John Wiley & Sons, Ltd.     

3‐butyl‐6‐fluoro‐1 (3H)‐isobenzofuranone,a derivative of dl‐n‐butylphthalide,attenuates hydrogen peroxide‐induced damage in PC12 cells

The anti‐cerebral ischemia agent, dl‐3‐n‐butylphthalide (NBP), is effective in models of vascular dementia in animals. The present study investigates the protective effect of 3‐butyl‐6‐fluoro‐1 (3H)‐isobenzofuranone (6‐F‐NBP), a fluoro derivative of dl‐nbutylphthalide, in hydrogen peroxide (H₂O₂)‐induced damage in PC12 cells. Exposure of PC12 cells to H₂O₂ for 24 h led to decreased cell survival, glutathione peroxidase (GSH‐PX), and mitochondrial membrane potential (MMP). In contrast, malondialdehyde (MDA) production, nitric oxide synthase (NOS) activity, nitric oxide (NO) formation, and intracellular reactive oxygen species (ROS) were increased, as was intracellular accumulation of [Ca²⁺]_i. However, pretreatment with 6‐F‐NBP markedly reversed the changes induced by H₂O₂, exhibiting a protective effect against H₂O₂‐induced cytotoxicity in PC12 cells. The compound may have therapeutic potential in the treatment of cerebral ischemia by inhibiting the oxidative damage. Drug Dev Res 72: 259–264, 2011. © 2010 Wiley‐Liss, Inc.     

4‐chloro‐1,2‐phenylenediamine Induces Apoptosis in Mardin–Darby canine kidney cells via activation of caspases

4‐Chloro‐1,2‐phenylenediamine (4‐Cl‐o‐PD) is a halogenated aromatic diamine that was used as a precursor for manufacturing permanent hair dyes. Despite its well‐documented mutagenic and carcinogenic effects in a number of in vitro and in vivo models, its cytotoxicity and mode of action have not received similar attention. Here, we investigated the effect of 4‐Cl‐o‐PD on Mardin–Darby canine kidney cells. It induced apoptosis and the evidence suggests its initiation by reactive oxygen species (ROS). The results of various assays used show a dose‐dependent (i) decrease in cell viability, (ii) increase in cells at sub‐G1 phase and the G0/G1 phase arrested in cell cycle, (iii) increase in intracellular ROS accompanied by depletion of glutathione, and (iv) that apoptotic cell death probably involves activation of both intrinsic and extrinsic pathways. © 2012 Wiley Periodicals, Inc. Environ Toxicol 29: 655–664, 2014.     

Design,Synthesis, and Antitumor Activity of (E,Z)‐1‐(dihydrobenzofuran‐5‐yl)‐3‐phenyl‐2‐(1,2,4‐triazol‐1‐yl)‐2‐propen‐1‐ones

A series of (E,Z)‐1‐(dihydrobenzofuran‐5‐yl)‐3‐phenyl‐2‐(1,2,4‐triazol‐1‐yl)‐2‐propen‐1‐ones ( C1 – C35 ) were designed and synthesized, and the structures of compounds (Z)‐ C27 and (Z)‐ C29 were confirmed by single‐crystal X‐ray diffraction. The antitumor activities of these novel compounds against cervical cancer (HeLa), lung cancer (A549), and breast cancer (MCF‐7) cell lines were evaluated in vitro. Majority of the title compounds exhibited strong antitumor activities and were much more promising than the positive control Taxol, which were also accompanied by lower cytotoxicity to normal cells. In particular, compounds (E,Z)‐ C24 exhibited the most consistent potent activities against three neoplastic cells with IC₅₀ values ranging from 3.2 to 7.1 μm . Further researches demonstrated that compounds (E,Z)‐ C24 could induce cell apoptosis and arrest cell cycle at the G2/M and S phases. Meanwhile, the structure–activity relationship between the configurations and cytotoxicity of the compounds was also investigated.     

Synthesis,docking studies,and pharmacological evaluation of 5HT2C ligands containing the N′‐cyanoisonicotinamidine or N′‐cyanopicolinamidine nucleus

N′‐Cyanoisonicotinamidine and N′‐cyanopicolinamidine derivatives, linked to an arylpiperazine moiety, were prepared and their affinities to the 5‐HT_1A, 5‐HT_2A, and 5‐HT_2C receptors were evaluated. Several of the newly synthesized compounds, tested by binding studies, showed nanomolar affinity at the 5‐HT_1A and 5‐HT_2C receptors and moderate or no affinity for other relevant receptors (D₁, D₂, α₁, and α₂). Compound 8e (K_i = 21.4 nM) was the most affine for the 5‐HT_2C receptor, showing, at the same time, a high selectivity with respect to the other receptors analyzed. Compounds 4a and 4c , instead, showed an interesting mixed 5‐HT_1A/5‐HT_2C activity with K_i values of 21.3/11.5 and 23.2/6.48 nM, respectively. The compounds with better affinity and selectivity binding profiles toward 5‐HT_2C ( 4a , 4c , 8b , and 8e ) were selected for further in vivo assays to determine their functional activity. Finally, to rationalize the obtained results, molecular docking studies were performed. The results of the pharmacological studies showed that compounds 4a , 8b , and 8e exerted antidepressant‐like effects and 4a and 8e revealed also significant anxiolytic properties. Among the developed derivatives, the most promising compound seems to be 4a , which displayed antipsychotic‐, antidepressant‐ and anxiolytic‐like properties. No side effects, like catalepsy, motor‐impairment or ethanol‐potentiating effects, were observed after the injection of the tested compounds.     

Exploration of 5‐(5‐nitrothiophen‐2‐yl)‐4,5‐dihydro‐1H‐pyrazoles as selective,multitargeted antimycobacterial agents

We report the biological evaluation of 5‐(5‐nitrothiophen‐2‐yl)‐4,5‐dihydro‐1H‐pyrazole derivatives against bacteria, eukaryotic cell lines and the assessment of their mechanisms of action to determine their prospects of being developed into potent antituberculosis agents. The compounds were evaluated for their antibacterial property against Mycobacterium tuberculosis H37Rv, multidrug‐resistant M. tuberculosis, Mycobacterium bovis BCG, Mycobacterium aurum, Escherichia coli, and Staphylococcus aureus using high‐throughput spot‐culture growth inhibition assay. They were found to be selective toward slow‐growing mycobacteria and Gram‐positive bacteria. In M. bovis BCG, they exhibited a bactericidal mode of action. Cytotoxicity was assessed in human THP‐1 and murine RAW 264.7 cell lines, and the compounds showed a lower cytotoxicity potential when compared with their antibacterial activity. They were found to be excellent whole‐cell efflux pump inhibitors of the mycobacterial surrogate M. aurum, performing better than known efflux pump inhibitor verapamil. The 5‐nitrothiophene moiety was identified for the first time as a prospective inhibitor scaffold of mycobacterial arylamine N‐acetyltransferase enzyme, which is the key enzyme in metabolizing isoniazid, a first‐line antituberculosis drug. The two aforementioned findings make the compounds potential hits in the development of adjunctive tuberculosis therapy.     

Synthesis and preliminary characterization of radioiodinated benzofuran‐3‐yl‐(indol‐3‐yl)maleimide derivatives as potential SPECT imaging probes for the detection of glycogen synthase kinase‐3β (GSK‐3β) in the brain

We report on the synthesis and preliminary characterization of two radioiodinated benzofuran‐3‐yl‐(indol‐3‐yl)maleimides, 3‐(benzofuran‐3‐yl)‐4‐(5‐[¹²⁵I]iodo‐1‐methyl‐1H‐indol‐3‐yl)‐1H‐pyrrole‐2,5‐dione ([¹²⁵I]5), and 3‐(5‐[¹²⁵I]iodo‐1‐methyl‐1H‐indol‐3‐yl)‐4‐(6‐methoxybenzofuran‐3‐yl)‐1H‐pyrrole‐2,5‐dione ([¹²⁵I]6), as the first potential SPECT imaging probes targeting glycogen synthase kinase‐3β (GSK‐3β). In this study, we used ¹²⁵I as a surrogate of ¹²³I because of its ease of use. The radioiodinated ligands were prepared from the corresponding tributyltin precursors through an iododestannylation reaction using hydrogen peroxide as an oxidant with a radiochemical yield of 10–30%. In vitro binding experiments suggested that both compounds show high affinity for GSK‐3β at a level similar to a known GSK‐3β inhibitor. Biodistribution studies with normal mice revealed that the radioiodinated compounds display sufficient uptake into (1.8%ID/g at 10 min postinjection) and clearance from the brain (1.0%ID/g at 60 min postinjection). These preliminary results suggest that the further optimization of radioiodinated benzofuran‐3‐yl‐(indol‐3‐yl)maleimide derivatives may facilitate the development of clinically useful SPECT imaging probes for the in vivo detection of GSK‐3β.     

Bioactive N‐terminal undecapeptides derived from parathyroid hormone: the role of α‐helicity*

Abstract: The N‐terminal 1–34 segment of parathyroid hormone (PTH) is fully active in vitro and in vivo and it can reproduce all biological responses in bone characteristic of the native intact PTH. Recent studies have demonstrated that N‐terminal fragments presenting the principal activating domain such as PTH(1–11) and PTH(1–14) with helicity‐enhancing substitutions yield potent analogues with PTH(1–34)‐like activity. To further investigate the role of α‐helicity on biological potency, we designed and synthesized by solid‐phase methodology the following hPTH(1–11) analogues substituted at positions 1 and/or 3 by the sterically hindered and helix‐promoting C^α‐tetrasubstituted α‐amino acids α‐amino isobutyric acid (Aib), 1‐aminocyclopentane‐1‐carboxylic acid (Ac₅c) and 1‐aminocyclohexane‐1‐carboxylic acid (Ac₆c): Ac₅c‐V‐Aib‐E‐I‐Q‐L‐M‐H‐Q‐R‐NH₂ ( I ); Aib‐V‐Ac₅c‐E‐I‐Q‐L‐M‐H‐Q‐R‐NH₂ ( II ); Ac₆c‐V‐Aib‐E‐I‐Q‐L‐M‐H‐Q‐R‐NH₂ ( III ); Aib‐V‐Ac₆c‐E‐I‐Q‐L‐M‐H‐Q‐R‐NH₂ ( IV ); Aib‐V‐Aib‐E‐I‐Q‐L‐M‐H‐Q‐R‐NH₂ ( V ); S‐V‐Aib‐E‐I‐Q‐L‐M‐H‐Q‐R‐NH₂ ( VI ), S‐V‐Ac₅c‐E‐I‐Q‐L‐M‐H‐Q‐R‐NH₂ ( VII ); Ac₅c‐V‐S‐E‐I‐Q‐L‐M‐H‐Q‐R‐NH₂ ( VIII ); Ac₆c‐V‐S‐E‐I‐Q‐L‐M‐H‐Q‐R‐NH₂ ( IX ); Ac₅c‐V‐Ac₅c‐E‐I‐Q‐L‐M‐H‐Q‐R‐NH₂ ( X ); Ac₆c‐V‐Ac₆c‐E‐I‐Q‐L‐M‐H‐Q‐R‐NH₂ ( XI ). All analogues were biologically evaluated and conformationally characterized in 2,2,2‐trifluoroethanol (TFE) solution by circular dichroism (CD). Analogues I – V , which cover the full range of biological activity observed in the present study, were further conformationally characterized in detail by nuclear magnetic resonance (NMR) and computer simulations studies. The results of ligand‐stimulated cAMP accumulation experiments indicated that analogues I and II are active, analogues III , VI and VII are very weakly active and analogues IV , V , VIII–XI are inactive. The most potent analogue, I exhibits biological activity 3500‐fold higher than that of the native PTH(1–11) and only 15‐fold weaker than that of the native sequence hPTH(1–34). Remarkably, the two most potent analogues, I and II , and the very weakly active analogues, VI and VII , exhibit similar helix contents. These results indicate that the presence of a stable N‐terminal helical sequence is an important but not sufficient condition for biological activity.     

Potent bradykinin antagonists containing N‐benzylglycine or N‐benzyl‐l‐alanine in position 8

Abstract: Two new analogues of a previously designed bradykinin (BK) antagonist, d ‐Arg‐Arg‐Pro‐Hyp‐Gly‐Thi‐Ser‐d ‐Phe‐Thi‐Arg, substituted in position 8 by N‐benzylglycine and N‐benzyl‐l ‐alanine were designed, synthesized and bioassayed. The results show an impressive enhancement of B₂ antagonistic potencies of both peptides in comparison with the model. In two further analogues these modifications were combined with acylation of the N‐terminus with 1‐adamantanacarboxylic acid. Acylated analogues exhibited higher antagonistic potency in comparison with the parent compounds, however, the range of effect was not as high as in previously described cases. The activity of analogues was assessed by their ability to inhibit vasodepressor response to exogenous BK (rat blood pressure test). Our results may be of value in the design of more potent BK antagonists.