Design,Synthesis, and Biological Evaluation of 1‐(thiophen‐2‐yl)‐9H‐pyrido[3,4‐b]indole Derivatives as Anti‐HIV‐1 Agents

A novel series of 1‐(thiophen‐2‐yl)‐9H‐pyrido [3,4‐b]indole derivatives were synthesized using DL‐tryptophan as starting material. All the compounds were characterized by spectral analysis such as ¹H NMR, Mass, IR, elemental analysis and evaluated for inhibitory potency against HIV‐1 replication. Among the reported analogues, compound 7g exhibited significant anti‐HIV activity with EC₅₀ 0.53 μm and selectivity index 483; compounds 7e , 7i , and 7o displayed moderate activity with EC₅₀ 3.8, 3.8, and 2.8 μm and selectivity index >105, >105, and 3.85, respectively. Interestingly, compound 7g inhibited p24 antigen expression in acute HIV‐1_IIIB infected cell line C8166 with EC₅₀ 1.1 μm . In this study, we also reported the Lipinski rule of 5 parameters, predicted toxicity profile, drug‐likeness, and drug score of the synthesized analogues.     

Synthesis and Anticonvulsant Activity of N‐(2‐Hydroxy‐ethyl)amide Derivatives

A series novel of N‐(2‐hydroxyethyl)amide derivatives was synthesized and screened for their anticonvulsant activities by the maximal electroshock (MES) test, and their neurotoxicity was evaluated by the rotarod test (Tox). The maximal electroshock test showed that N‐(2‐hydroxyethyl)decanamide 1g , N‐(2‐hydroxyethyl)palmitamide 1l , and N‐(2‐hydroxyeth‐yl)stearamide 1n were found to show a better anticonvulsant activity and also had lower toxicity than the marked anti‐epileptic drug valproate. In the anti‐MES potency test, these compounds exhibited median effective doses (ED₅₀) of 22.0, 23.3, 20.5 mg/kg, respectively, and median toxicity doses (TD₅₀) of 599.8, >1000, >1000 mg/kg, respectively, resulting in a protective index (PI) of 27.5, >42.9, >48.8, respectively. This is a much better protective index than that of the marked anti‐epileptic drug valproate (PI = 1.6). To further investigate the effects of the anticonvulsant activity in several different models, compounds 1g , 1l , and 1n were tested having evoked convulsions with chemical substances, including pentylenetetrazloe, isoniazide, 3‐mercaptopropionic acid, bicuculline, thiosemicarbazide, and strychnine.     

Synthesis,biological evaluation,and molecular docking studies of novel 3‐aryl‐5‐(alkyl‐thio)‐1H‐1,2,4‐triazoles derivatives targeting Mycobacterium tuberculosis

A small library of new 3‐aryl‐5‐(alkyl‐thio)‐1H‐1,2,4‐triazoles was synthesized and screened for the antimycobacterial potency against Mycobacterium tuberculosis H₃₇Ra strain and Mycobacterium bovis BCG both in active and dormant stage. Among the synthesized library, 25 compounds exhibited promising anti‐TB activity in the range of IC₅₀0.03–5.88 μg/ml for dormant stage and 20 compounds in the range of 0.03–6.96 μg/ml for active stage. Their lower toxicity (>100 μg/ml) and higher selectivity (SI = >10) against all cancer cell lines screened make them interesting compounds with potential antimycobacterial effects. Furthermore, to rationalize the observed biological activity data and to establish a structural basis for inhibition of M. tuberculosis, the molecular docking study was carried out against a potential target MTB CYP121 which revealed a significant correlation between the binding score and biological activity for these compounds. Cytotoxicity and in vivo pharmacokinetic studies suggested that 1,2,4‐triazole analogues have an acceptable safety index, in vivo stability and bio‐availability.     

New alkenyl derivative from Piper malacophyllum and analogues: Antiparasitic activity against Trypanosoma cruzi and Leishmania infantum

Alkylphenols isolated from Piper malacophyllum (Piperaceae), gibbilimbols A and B, showed interesting activity against the parasites Trypanosoma cruzi and Leishmania infantum. In continuation to our previous work, a new natural product from the essential oil of the leaves of P. malacophyllum was isolated, the 5‐[(3E)‐oct‐3‐en‐1‐il]‐1,3‐benzodioxole, and also a new set of five compounds was prepared. The antiparasitic activity of the natural product was evaluated in vitro against these parasites, indicating potential against the promastigote/trypomastigote/amastigote forms (IC₅₀ 32–83 μm ) of the parasites and low toxicity (CC₅₀ > 200 μm ) to mammalian cells. The results obtained to the synthetic compounds indicated that the new derivatives maintained the promising antiparasitic activity, but the cytotoxicity was considerably lowered. The amine derivative LINS03011 displayed the most potent IC₅₀ values (13.3 and 16.7 μm ) against amastigotes of T. cruzi and L. infantum, respectively, indicating comparable activity to the phenolic prototype LINS03003, with threefold decreased (CC₅₀ 73.5 μm ) cytotoxicity, leading the selectivity index (SI) towards the parasites up to 24.5. In counterpart, LINS03011 has not shown membrane disruptor activity in SYTOX Green model. In summary, this new set showed the hydroxyl is not essential for the antiparasitic activity, and its substitution could decrease the toxicity to mammalian cells.     

Multilaboratory evaluation of 15 bioassays for (eco)toxicity screening and hazard ranking of engineered nanomaterials: FP7 project NANOVALID

Within EU FP7 project NANOVALID, the (eco)toxicity of 7 well-characterized engineered nanomaterials (NMs) was evaluated by 15 bioassays in 4 laboratories. The highest tested nominal concentration of NMs was 100?mg/l. The panel of the bioassays yielded the following toxicity order: Ag?>?ZnO?>?CuO?>?TiO_2?>_?MWCNTs?>?SiO_2?>_?Au. Ag, ZnO and CuO proved very toxic in the majority of assays, assumingly due to dissolution. The latter was supported by the parallel analysis of the toxicity of respective soluble metal salts. The most sensitive tests/species were Daphnia magna (towards Ag NMs, 24-h EC_50?=_?0.003?mg Ag/l), algae Raphidocelis subcapitata (ZnO and CuO, 72-h EC_50?=_?0.14?mg Zn/l and 0.7?mg Cu/l, respectively) and murine fibroblasts BALB/3T3 (CuO, 48-h EC_50?=_?0.7?mg Cu/l). MWCNTs showed toxicity only towards rat alveolar macrophages (EC_50?=_?15.3?mg/l) assumingly due to high aspect ratio and TiO₂ towards R. subcapitata (EC_50?=_?6.8?mg Ti/l) due to agglomeration of TiO₂ and entrapment of algal cells. Finally, we constructed a decision tree to select the bioassays for hazard ranking of NMs. For NM testing, we recommend a multitrophic suite of 4 in vitro (eco)toxicity assays: 48-h D. magna immobilization (OECD202), 72-h R. subcapitata growth inhibition (OECD201), 30-min Vibrio fischeri bioluminescence inhibition (ISO2010) and 48-h murine fibroblast BALB/3T3 neutral red uptake in vitro (OECD129) representing crustaceans, algae, bacteria and mammalian cells, respectively. Notably, our results showed that these assays, standardized for toxicity evaluation of “regular” chemicals, proved efficient also for shortlisting of hazardous NMs. Additional assays are recommended for immunotoxicity evaluation of high aspect ratio NMs (such as MWCNTs).     

Design,synthesis, biological evaluation,and docking study of 4‐isochromanone hybrids bearing N‐benzyl pyridinium moiety as dual binding site acetylcholinesterase inhibitors (part II)

A series of novel 4‐isochromanone compounds bearing N‐benzyl pyridinium moiety were designed and synthesized as acetylcholinesterase (AChE) inhibitors. The biological evaluation showed that most of the target compounds exhibited potent inhibitory activities against AChE. Among them, compound 1q possessed the strongest anti‐AChE activity with an IC₅₀ value of 0.15 nm and high AChE/BuChE selectivity (SI > 5,000). Moreover, compound 1q had low toxicity in normal nerve cells and was relatively stable in rat plasma. Together, the current finding may provide a new approach for the discovery of novel anti‐Alzheimer's disease agents.     

Identification of dehydroxy isoquine and isotebuquine as promising antileishmanial agents

Traditional antimalarial drugs based on 4‐aminoquinolines have exhibited good antiproliferative activities against Leishmania parasites; however, their clinical use is currently limited. To identify new 4‐aminoquinolines to combat American cutaneous leishmaniasis, we carried out a full in vitro evaluation of a series of dehydroxy isoquines and isotebuquines against two Leishmania parasites such as Leishmania braziliensis and Leishmania mexicana. First, the antiproliferative activity of the quinolines was studied against the promastigote forms of L. braziliensis and L. mexicana parasites, finding that five of them exhibited good antileishmanial responses with micromolar IC₅₀ values ranging from 3.84 to 10 μM. A structure‐activity relationship analysis gave evidence that a piperidine or a morpholine attached as N‐alkyamino terminal substituent as well as the inclusion of an extra phenyl ring attached at the aniline ring of the isotebuquine core constitute important pharmacophores to generate the most active derivatives, with antileishmanial responses by far superior to those found for the reference drug, glucantime. All compounds showed a relatively low toxicity on human dermis fibroblasts, with CC₅₀ ranging from 69 to >250 μM. The five most active compounds displayed moderate to good antileishmanial activity against the intracellular amastigote form of L. braziliensis, compared to the reference drug. In particular, compound 2j was identified as the most potent agent against antimony‐resistant amastigotes of L. braziliensis with acceptable biological response and selectivity, emerging as a promising candidate for further in vivo antileishmanial evaluation. Diverse mechanism‐of‐action studies and molecular docking simulations were performed for the most active 4‐aminoquinoline.     

Synthesis and Antitumor Activity of Novel Nitrogen Mustard‐Linked Chalcones

A series of nitrogen mustard‐linked chalcones were synthesized and evaluated for their antitumor activity in vitro against the K562 and HepG2 cell lines. The aldol condensation of [N,N‐bis(chloroethyl)‐3‐amino]‐acetophenone ( 2 ) with aromatic aldehydes afforded the nitrogen mustard‐linked chalcones. Among the analogs tested, compounds 5e and 5k exhibited significant anti‐proliferation activities against K562 cells with IC₅₀ values of 2.55 and 0.61 µM, respectively, which revealed higher cell toxicity than the standard drugs cisplatin (IC₅₀ > 200 µM) and adriamycin (IC₅₀ = 14.88 µM). The methoxyl and N,N‐dimethyl groups on the B‐ring of the chalcone frame enhanced the inhibitory activities against both the K562 and HepG2 cell lines. The structure–activity relationship study indicated that the inhibitory activities significantly varied with the position(s) and species of the substituted group(s).     

Effect of 3‐Alkylpyridine Marine Alkaloid Analogues in Leishmania Species Related to American Cutaneous Leishmaniasis

A series of oxygenated analogues of marine 3‐alkylpyridine alkaloids were synthesized, and their leishmanicidal activity was assayed. All compounds were prepared from 3‐pyridinepropanol in few steps and in good yields. The key step for the synthesis of these compounds was a classic Williamson etherification under phase‐transfer conditions. Besides toxicity in peritoneal macrophages, the compounds exhibited a significant leishmanicidal activity. Of twelve compounds tested, five showed a strong leishmanicidal activity against promastigote forms of Leishmania amazonensis and L. braziliensis with IC₅₀ below 10 μm . Compounds 11 , 14 , 15, and 16 showed a strong leishmanicidal activity on intracellular amastigotes (IC₅₀ values of 2.78; 0.27; 1.03, and 1.33 μm , respectively), which is unlikely to be owing to the activation of nitric oxide production by macrophages.     

Some Hydrazones of 2‐Aroylamino‐3‐methylbutanohydrazide: Synthesis,Molecular Modeling Studies,and Identification as Stereoselective Inhibitors of HIV‐1

In accordance with our antiviral drug development attempt, acylhydrazone derivatives bearing amino acid side chains were synthesized for the evaluation of their antiviral activity against various types of viruses. Among these compounds, 8 _S , 11 _S , and 12 _S showed anti‐HIV‐1 activity with a 50% inhibitory concentration (IC₅₀) = 123.8 µM (selectivity index, SI > 3), IC₅₀ = 12.1 µM (SI > 29), IC₅₀ = 17.4 µM (SI > 19), respectively. Enantiomers 8 _R , 11 _R , and 12 _R were inactive against the HIV‐1 strain III_B. Hydrazones 8 _S , 11 _S , and 12 _S which were active against HIV‐1 wild type showed no inhibition against a double mutant NNRTI‐resistant strain (K103N;Y181C). Molecular docking calculations of R‐ and S‐enantiomers of 8 , 11 , and 12 were performed using the hydrazone‐bound novel site of HIV‐1 RT.     

Synthesis and Biological Evaluation of Pyrazoline Derivatives Bearing an Indole Moiety as New Antimicrobial Agents

1‐(p‐Methylphenyl)‐3,5‐diaryl‐2‐pyrazoline derivatives ( 2a–f ) were synthesized via the treatment of 1‐(1H‐indol‐3‐yl)‐3‐aryl‐2‐propen‐1‐ones ( 1a–f ) with p‐methylphenylhydrazine hydrochloride in hot acetic acid. The structures of these compounds were elucidated by IR, ¹H NMR, and mass spectral data and elemental analysis. These compounds were investigated for their antimicrobial activity. Brine‐Shrimp lethality assay was carried out to determine the toxicity of the compounds. Compound 2e , which is the pyrazoline derivative bearing the 2,5‐dichlorophenyl moiety, can be identified as the most promising agent against Klebsiella pneumoniae (ATCC 13883) and Candida glabrata (ATCC 36583) due to its inhibitory effects on K. pneumoniae and C. glabrata with a MIC value of 100 µg/mL as a non‐toxic agent (LC₅₀ > 1000 µg/mL).     

Assessment of Leishmanicidal and Trypanocidal Activities of Aliphatic Diamine Derivatives

Leishmanicidal and trypanocidal activity of seventeen lipophilic diamines was evaluated in vitro against Leishmania braziliensis, L. chagasi, and Trypanosoma cruzi. Twelve compounds presented anti‐Leishmania and six showed anti‐T. cruzi amastigote activity. Compound 14 (N‐tetradecyl‐1,4‐butanediamine) was the most active against both L. braziliensis (IC₅₀ = 2.6 μm ) and L. chagasi (IC₅₀ = 3.0 μm ) which showed a selectivity index (SI) >100. N‐decyl‐1,6‐hexanediamine (compound 9 ) presented an IC₅₀ = 1.6 μm and SI >187 and was over six times more potent than the reference drug benznidazole against T. cruzi. Treatment of infected or uninfected macrophages with compounds 9 and 14 did not induce significant TNFα and NO production. Four compounds ( 15 , 16 , 22 , and 23 ) inhibited 78.9%, 77.7%, 83.7%, and 70.1% of rTRLb activity, respectively, and compound 23 inhibited 73.3% of rTRTc activity at 100 μm . A concentration‐dependent effect on mitochondrial membrane depolarization was observed in T. cruzi epimastigotes treated with compound 9 , suggesting this mechanism may be involved in the trypanocidal effect. On the contrary, in L. braziliensis promastigotes treated with compound 14 , no mitochondrial depolarization was observed. Our results demonstrate that N‐decyl‐1,6‐hexanediamine and N‐tetradecyl‐1,4‐butanediamine are promising molecules for the development of novel leading compounds against T. cruzi and Leishmania spp., particularly given a possible alternative mechanism of action.     

Evaluation of Structurally Diverse Benzoazepines Clubbed with Coumarins as Mycobacterium tuberculosis Agents

Tuberculosis caused by Mycobacterium tuberculosis remains a leading cause of mortality worldwide into 21st century. In continuation with our anti‐tuberculosis research programme, in this work, we have prepared molecularly diverse coumarins clubbed with benzothiazepines as well as its aza‐analogues‐benzodiazepines by molecular hybridization. The resulting compounds were screened for their M. tuberculosis activity against H₃₇Rv strains using microplate alamar blue assay. Among the designed diversity, the compounds 5k, 5n and 5o were found significantly active in primary anti‐tuberculosis assay at minimum inhibitory concentration <6.25 μm . Moreover, the IC₅₀ values of 5k and 5o in level‐2 screening were observed as >10 μg/mL and 3.63 μg/mL, respectively. Design and synthesis of more focused library and its three‐dimensional quantitative structure activity relationship analysis are underway.     

Basic apoptotic and necrotic cell death in human liver carcinoma (HepG2) cells induced by synthetic azamacrocycle

Treatment of diseases with synthetic materials has been an aspiration of mankind since the dawn of human development. In this research, three complex compounds of azamacrocycle (TD1, TD2, and TD3) were synthesized, and experiments were conducted to determine whether their toxicity to human liver carcinoma (HepG₂) cells is associated with apoptotic and/or necrotic cell death. Cell survival was determined by MTT assay. Apoptosis and necrosis were measured by annexin V FITC/PI assay using the flow cytometry and by propidium iodide (PI) assay using the cellometer vision. HepG₂ cells were treated with different concentrations of azamacrocycles for 48 h. Results from MTT assay indicated that all the three azamacrocycles significantly (p < 0.05) reduce cell viability in a dose‐dependent manner, showing 48 h‐LD₅₀ values of about 37.97, 33.60, and 19.29 μM, for TD3, TD1 and TD2, respectively. Among the three compounds tested, TD2 showed the most pronounced cytotoxic activity against HepG₂ cells, being about twofold more potent than TD3. The order of toxicity was TD2 > TD1 > TD3. Because TD2 exerted the most cytotoxic activity against HepG₂ cells, it was used in the subsequent apoptosis and necrosis‐related experiments. The flow cytometry assessment showed a strong dose‐response relationship with regard to TD2 exposure and annexin V/PI positive cells. PI assay data indicated that TD2 exposure increased the proportion of fluorescence positive cells. Overall, our results indicate that azamacrocycle toxicity to HepG₂ cells is associated with apoptotic and necrotic cell death resulting from phosphatidylserine externalization and loss of membrane integrity. © 2012 Wiley Periodicals, Inc. Environ Toxicol 29: 605–611, 2014.     

In vitro activity profiling of Cumyl‐PEGACLONE variants at the CB1 receptor: Fluorination versus isomer exploration

Synthetic cannabinoid receptor agonists (SCRAs) are one of the largest groups of new psychoactive substances monitored in Europe. SCRAs are known to typically exert higher cannabinoid activity than tetrahydrocannabinol from cannabis, thereby entailing a greater health risk. Both Cumyl‐PEGACLONE and 5F‐Cumyl‐PEGACLONE were not controlled by the national legislation upon their first detection in Germany in 2016 and 2017, respectively, and have been linked to several fatalities. In this study, the CB₁ receptor activity of these compounds, together with two newly synthesized structural isomers (Cumyl‐PEGACLONE ethylbenzyl isomer and n‐propylphenyl isomer), was assessed using two different in vitro receptor‐proximal bioassays, monitoring the recruitment of either β‐arrestin2 (β‐arr2) or a modified G protein (mini‐Gα_i) to the activated CB₁ receptor. In terms of both potency and relative efficacy, Cumyl‐PEGACLONE and 5F‐Cumyl‐PEGACLONE were found to exert strong CB₁ activation, with sub‐nanomolar EC₅₀ values and efficacy values exceeding those of the reference agonist JWH‐018 threefold (β‐arr2 assay) or almost twofold (mini‐Gα_i assay). The ethylbenzyl and n‐propylphenyl isomers exhibited a strongly reduced CB₁ activity (EC₅₀ values >100 nM; efficacy <40% relative to JWH‐018), which is hypothesized to originate from steric hindrance in the ligand‐binding pocket. None of the evaluated compounds exhibited significant biased agonism. In conclusion, the functional assays applied here allowed us to demonstrate that 5‐fluorination of Cumyl‐PEGACLONE is not linked to an intrinsically higher CB₁ activation potential and that the ethylbenzyl and n‐propylphenyl isomers yield a strongly reduced CB₁ activation.     

Secochiliolide ester derivatives: Preparation and evaluation of their antitrypanosomal and antimalarial efficacy

In the present study, a series of new esters of secochiliolide acid (SA), a diterpene isolated from Nardophyllum bryoides, were synthesized in good yield. All compounds were evaluated for their in vitro antiparasitic properties (on Plasmodium falciparum and Trypanosoma brucei brucei) and cytotoxicity (on WI38, normal mammalian cells). They displayed moderate antitrypanosomal activity with IC₅₀ values between 2.55 and 18.14 μm , with selectivity indices >10, and low antiplasmodial effects with IC₅₀ > 29 μm . The only exception was the n‐hexyl ester of SA, which showed a strong and selective antiplasmodial activity (IC₅₀ = 1.99 μm and selectivity index = 117.0). The in vivo antimalarial efficacy of this compound was then assessed according to the 4‐day suppressive test of Peters in mice. An intraperitoneal treatment at 50 mg kg^?1 day^?1 induced a slight parasitaemia reduction by 56% which was statistically significant on day 4 post‐infection and an increase in the survival time.     

Synthesis and calcium channel modulation effects of isopropyl 1,4‐dihydro‐2,6‐dimethyl‐3‐nitro‐4‐phenylpyridine‐5‐carboxylates possessing ortho‐, meta‐, and para‐CH2S(O)nMe and –S(O)nMe (n = 0–2) phenyl substituents

A group of isopropyl 1,4‐dihydro‐2,6‐dimethyl‐3‐nitro‐4‐phenylpyridine‐5‐carboxylates ( 13–15 ) possessing ortho‐, meta‐, and para‐CH₂S(O)nMe and –S(O)nMe (n = 0–2) phenyl substituents were synthesized using a modified Hantzsch reaction. Calcium channel (CC) modulating activities were determined using guinea pig ileum longitudinal smooth muscle (GPILSM) and guinea pig left atrium (GPLA) in vitro assays. This class of –CH₂S(O)nMe and –S(O)nMe (n = 0–2) compounds ( 13–15a–f ) exhibited weaker CC antagonist activity on GPILSM (IC₅₀ = > 1.1 × 10^–5 to 4.1 × 10^–6 M range) than the reference drug nifedipine (IC₅₀ = 1.4 × 10^–8 M). The oxidation state of the sulfur atom was a determinant of smooth muscle CC antagonist activity where the relative activity profile was generally thio ( 13 , ‐CH₂SMe, ‐SMe) and sulfonyl ( 15 , ‐CH₂SO₂Me, ‐SO₂Me) > sulfinyl ( 14 , ‐CH₂SOMe, ‐SOMe). The point of attachment of the phenyl substituent was a determinant of activity for the –CH₂SMe ( 13a–c ), ‐CH₂SOMe ( 14a–c ) and SOMe ( 14d–f ) isomers where the relative potency order was meta and para > ortho. Compounds in this group ( 13–15 ), unlike Bay K 8644 (EC₅₀ = 2.3 × 10^–7 M on GPILSM), did not exhibit an agonist effect on GPILSM. The meta‐CH₂SMe ( 13b ), ortho‐CH₂SMe ( 13c ), meta‐SMe ( 13e ), and ortho‐CH₂SO₂Me ( 15c ) C‐4 phenyl derivatives exhibited respectable in vitro cardiac positive inotropic activities (EC₅₀ = 1.00 × 10^–6 to 7.57 × 10^–6 M range) relative to the reference drug Bay K 8644 (EC₅₀ = 7.70 × 10^–7 M) in the GPLA assay. In contrast to Bay K 8644, which acts as an undesirable calcium channel agonist on smooth muscle (GPILSM), compounds 13b (IC₅₀ = 4.11 × 10^–6 M), 13c (IC₅₀ = 2.29 × 10^–5 M), 13e (IC₅₀ = > 1.20 × 10^–5 M) and 15c (IC₅₀ = 6.22 × 10^–6 M) exhibited a desirable simultaneous calcium channel antagonist effect on smooth muscle at a similar ( 13b , 15c ), or lower ( 13c , 13e ), concentration relative to its cardiac agonist EC₅₀ value. Model compounds such as 13b , 13c , 13e , and 15c , that exhibit dual cardioselective agonist / smooth muscle selective antagonist activities, represent a novel type of 1,4‐dihydropyridine CC modulators that offer a potential approach to drug discovery targeted toward the treatment of congestive heart failure and for use as probes to study the structure–function relationship of calcium channels. Drug Dev. Res. 51:177–186, 2000. © 2001 Wiley‐Liss, Inc.     

Design,synthesis and antitrypanosomatid activities of 3,5‐diaryl‐isoxazole analogues based on neolignans veraguensin,grandisin and machilin G

Using bioisosterism as a medicinal chemistry tool, 16 3,5‐diaryl‐isoxazole analogues of the tetrahydrofuran neolignans veraguensin, grandisin and machilin G were synthesized via 1,3‐dipolar cycloaddition reactions, with yields from 43% to 90%. Antitrypanosomatid activities were evaluated against Trypanosoma cruzi, Leishmania (L.) amazonensis and Leishmania (V.) braziliensis. All compounds were selective for the Leishmania genus and inactive against T. cruzi. Isoxazole analogues showed a standard activity on both promastigotes of L. amazonensis and L. braziliensis. The most active compounds were 15 , 16 and 19 with IC₅₀ values of 2.0, 3.3 and 9.5 μM against L. amazonensis and IC₅₀ values of 1.2, 2.1 and 6.4 μM on L. braziliensis, respectively. All compounds were noncytotoxic, showing lower cytotoxicity (>250 μM) than pentamidine (78.9 μM). Regarding the structure–activity relationship (SAR), the methylenedioxy group was essential to antileishmanial activity against promastigotes. Replacement of the tetrahydrofuran nucleus by an isoxazole core improved the antileishmanial activity.     

Automated swimming activity monitor for examining temporal patterns of toxicant effects on individual Daphnia magna

Aquatic pollutants are often biologically active at low concentrations and impact on biota in combination with other abiotic stressors. Traditional toxicity tests may not detect these effects, and there is a need for sensitive high‐throughput methods for detecting sublethal effects. We have evaluated an automated infra‐red (IR) light‐based monitor for recording the swimming activity of Daphnia magna to establish temporal patterns of toxicant effects on an individual level. Activity was recorded for 48 h and the sensitivity of the monitor was evaluated by exposing D. magna to the reference chemicals K₂Cr₂O₇ at 15, 20 and 25 °C and 2,4‐dichlorophenol at 20 °C. Significant effects (P < 0.001) of toxicant concentrations, exposure time and incubation temperatures were observed. At 15 °C, the swimming activity remained unchanged for 48 h at sublethal concentrations of K₂Cr₂O₇ whereas activity at 20 and 25 °C was more biphasic with decreases in activity occurring after 12–18 h. A similar biphasic pattern was observed after 2,4‐dichlorophenol exposure at 20 °C. EC₅₀ values for 2,4‐dichlorophenol and K₂Cr₂O₇ determined from automated recording of swimming activity showed increasing toxicity with time corresponding to decreases in EC₅₀ of 0.03–0.07 mg l^–1 h^–1. EC₅₀ values determined after 48 h were comparable or lower than EC₅₀ values based on visual inspection according to ISO 6341. The results demonstrated that the swimming activity monitor is capable of detecting sublethal behavioural effects that are toxicant and temperature dependent. The method allows EC values to be established at different time points and can serve as a high‐throughput screening tool in toxicity testing. Copyright © 2015 John Wiley & Sons, Ltd.