Methnaridine is an orally bioavailable,fast‐killing and long‐acting antimalarial agent that cures Plasmodium infections in mice

Background and PurposeMalaria is one of the deadliest diseases in the world. Novel chemotherapeutic agents are urgently required to combat the widespread Plasmodium resistance to frontline drugs. Here, we report the discovery of a novel benzonaphthyridine antimalarial, methnaridine, which was identified using a structural optimization strategy.Experimental ApproachAn integrated pharmacological approach was used to evaluate the antimalarial profile of methnaridine. The pharmacokinetic properties of methnaridine were investigated along with the associated safety profile. Host immune response patterns were also analysed.Key ResultsMethnaridine exhibited potent antimalarial activity against P. falciparum (3D7: IC₅₀ = 0.0066 μM; Dd2: IC₅₀ = 0.0056 μM). In P. berghei‐infected mice, oral administration effectively suppressed parasitemia (ED₅₀ = 0.52 mg·kg⁻¹·day⁻¹) and cured the established infection (CD₅₀ = 10.13 mg·kg⁻¹·day⁻¹). These results are equivalent to or better than those of other antimalarial agents in clinical use. Notably, a four‐dose oral regimen at a dosage of 25 mg·kg⁻¹ achieved a complete cure of P. berghei infection in mice. Methnaridine exhibited a rapid parasiticidal profile (PCT₉₉ = 36.0 h) and showed no cross‐resistance to chloroquine. Pharmacokinetic studies revealed that methnaridine is readily absorbed, long‐lasting and slowly cleared. The safety profile of methnaridine is also satisfactory (maximum tolerated dose = 1,125 mg·kg⁻¹). In addition, following methnaridine treatment, infection‐induced Th1 immune response was almost fully alleviated in mice.Conclusion and ImplicationsMethnaridine is an orally bioavailable, fast‐acting and long‐lasting agent with excellent antimalarial properties. Our study highlights the potential of methnaridine for clinical development as a promising antimalarial candidate.     

Antimalarial,antiplasmodial and analgesic activities of root extract of Alchornea laxiflora

Context: Alchornea laxiflora (Benth.) Pax. &; Hoffman (Euphorbiaceae) root decoctions are traditionally used in the treatment of malaria and pain in Nigeria.

Objective: To assess the antimalarial, antiplasmodial and analgesic potentials of root extract and fractions against malarial infections and chemically-induced pains.

Material and methods: The root extract and fractions of Alchornea laxiflora were investigated for antimalarial activity against Plasmodium berghei infection in mice, antiplasmodial activity against chloroquine sensitive (Pf 3D7) and resistant (Pf INDO) strains of Plasmodium falciparum using SYBR green assay method and analgesic activity against experimentally-induced pain models. Acute toxicity study of the extract, cytotoxic activity against HeLa cells and GCMS analysis of the active fraction were carried out.

Results: The root extract (75–225?mg/kg, p.o.) with LD₅₀ of 748.33?mg/kg exerted significant (p?P. berghei infection in suppressive, prophylactive and curative tests. The root extract and fractions also exerted moderate activity against chloroquine sensitive (Pf 3D7) and resistant (Pf INDO) strains of P. falciparum with the ethyl acetate fraction exerting the highest activity with IC₅₀ value of 38.44?±?0.89?μg/mL (Pf 3D7) and 40.17?±?0.78?μg/mL (Pf INDO). The crude extract was not cytotoxic to HeLa cells with LC₅₀ value >100?μg/mL. The crude extract and ethyl acetate fraction exerted significant (p?Discussion and conclusions: These results suggest that the root extract/fractions of A. laxiflora possess antimalarial, antiplasmodial and analgesic potentials and these justify its use in ethnomedicine to treat malaria and pain.     

Antimalarial quassinoids: past,present and future

This review is a compilation of the investigations reported to date on the sources, isolation, chemistry and antimalarial activities of natural quassinoids and their synthetic and semisynthetic analogs. It also provides an analysis of the in vitro structure–activity relationship of quassinoids for further evaluation in animal models. The introduction of non-nitrogenous antimalarial drugs has created a new era of malaria chemotherapy to treat Plasmodium falciparum strains that are resistant to existing nitrogenous drugs and the rising incidence of the deadly cerebral malaria. Many antimalarial quassinoids are discovered from simaroubaceous plants that are used traditionally to treat fever and malaria, thereby reiterating the critical role of ethnopharmacology as a rich source of novel drug discovery.     

Isolation,crystal structure determination and cholinesterase inhibitory potential of isotalatizidine hydrate from Delphinium denudatum

Context: Delphinium denudatum Wall (Ranunculaceae) is a rich source of diterpenoid alkaloids and is widely used for the treatment of various neurological disorders such as epilepsy, sciatica and Alzheimer’s disease.

Objective: The present study describes crystal structure determination and cholinesterase inhibitory potential of isotalatazidine hydrate isolated from the aerial part of Delphinium denudatum.

Materials and methods: Phytochemical investigation of Delphinium denudatum resulted in the isolation of isotalatazidine hydrate in crystalline form. The molecular structure of the isolated compound was established by X-ray diffraction. The structural data (bond length and angles) of the compound were calculated by Density Functional Theory (DFT) using B3LYP/6-31?+?G (p) basis set. The cholinesterase inhibitory potential of the isolated natural product was determined at various concentrations (62.5, 125, 250, 500 and 1000?μg/mL) followed by molecular docking to investigate the possible inhibitory mechanism of isotalatazidine hydrate.

Results: The compound crystallized in hexagonal unit cell with space group P6_5. Some other electronic properties such as energies associated with HOMO-LUMO, band gaps, global hardness, global electrophilicity, electron affinity and ionization potential were also calculated by means of B3LYP/6-31?+?G (p) basis set. The compound showed competitive type inhibition of both acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) with IC₅₀ values of 12.13?μM and 21.41?μM, respectively.

Discussion and conclusion: These results suggest that isotalatazidine hydrate is a potent dual cholinesterase inhibitor and can be used as a target drug in Alzheimer diseases. This is first report indicating isotalatazidine hydrate with anticholinesterase potential.     

Quinic acid derivatives as sialyl Lewis(x)-mimicking selectin inhibitors: design, synthesis, and crystal structure in complex with E-selectin

A search for noncarbohydrate sLe(x) mimics led to the development of quinic acid derivatives as selectin inhibitors. At Wyeth we solved the first cocrystal structure of a small molecule, quinic acid, with E-selectin. In the cocomplex two hydroxyls of quinic acid mimic the calcium-bound fucose of the tetrasaccharide sLe(x). The X-ray structure, together with structure based computational methods, was used to design quinic acid based libraries that were synthesized and evaluated for their ability to block the interaction of sLex with P-selectin. A large number of analogues were prepared using solution-phase parallel synthesis. Selected compounds showed decrease in leukocyte rolling in the IVM mouse model. Compound 2 inhibited neutrophil influx in the murine TIP model and demonstrated good plasma exposure.     

Design, synthesis, and crystal structure of selective 2-pyridone tissue factor VIIa inhibitors

Targeted 2-pyridones were selected as tissue Factor VIIa inhibitors and prepared from 2,6-dibromopyridine via a multistep synthesis. A variety of chemical transformations, including regioselective nucleophilic addition, selective nitrogen alkylation, and a Suzuki coupling, afforded the targeted tissue Factor VIIa inhibitors. The pyridone core was selected as a replacement for the pyrazinone core of noncovalent tissue Factor VIIa inhibitors and designed such that their substitution pattern would occupy and interact with the S(1), S(2), and S(3) pockets of the tissue Factor VIIa enzyme. These compounds were tested in several serine protease enzyme assays involved in the coagulation cascade exhibiting modest activity on tissue Factor VIIa with excellent selectivity over thrombin and Factor Xa. Finally, an X-ray crystal structure of inhibitor 14a bound to tissue Factor VIIa was obtained and will be described.     

Differential inhibition of cytochrome P450 isoforms by the protease inhibitors, ritonavir, saquinavir and indinavir

Aims To compare the inhibitory potential of the HIV protease inhibitors saquinavir, ritonavir and indinavir against CYP1A2, CYP2C9, CYP2E1 and CYP3A4 catalysed metabolic reactions in human liver microsomes in vitro .
Methods Microsomes from six human livers were utilized in this study. The probe substrates were phenacetin (CYP1A2), tolbutamide (CYP2C9), chlorzoxazone (CYP2E1) and testosterone (CYP3A4). Metabolites were analysed by high performance liquid chromatography. I C ₅₀ (concentration of inhibitor giving 50% decrease in enzyme activity) and, where appropriate, K _i values were calculated.
Results Ritonavir was a very potent inhibitor of CYP3A4 mediated testosterone 6β-hydroxylation (mean K _i=0.019±0.004  μm, mean±s.d.; n =6) and also inhibited tolbutamide hydroxylation (I C ₅₀=4.2±1.3  μm, mean±s.d.; n =6). Inhibition of phenacetin O -deethylation and chlorzoxazone 6-hydroxylation was negligible. Indinavir was an order-of-magnitude less potent in inhibiting CYP3A4 ( K _i=0.17±0.01  μm ) and did not produce appreciable inhibition of the CYP1A2, CYP2C9 or CYP2E1 catalysed reactions. Saquinavir was the least potent CYP3A4 inhibitor ( K _i =2.99±0.87  μm ) and produced some inhibition of CYP2C9 (approximately 50% at 50  μm ).
Conclusions The HIV protease inhibitors have differential effects on CYP isozymes. There is obvious potential for clinically significant drug interactions particularly with ritonavir. Pharmacokinetic drug interaction studies are crucial to gain an overall understanding of the beneficial and potentially harmful effects of this important group of drugs.     

Secondary structure peptide mimetics: design, synthesis, and evaluation of beta-strand mimetic thrombin inhibitors

Constrained dipeptide mimetic templates were designed to mimic the secondary structure of peptides in a beta-strand conformation. Two templates corresponding to the D-Phe-Pro portion of the thrombin inhibitor D-Phe-Pro-ArgCH2Cl were synthesized and converted into nine alpha-ketoamide and alpha-ketoheterocycle inhibitors of thrombin. Additionally, a template corresponding to L-Phe-Pro was synthesized and converted to a thrombin inhibitor. The in vitro inhibition of thrombin by these compounds was determined, and those corresponding to the D-Phe-Pro were found to be more potent inhibitors than the L-Phe-Pro mimetic. The alpha-ketoamides were found to be more potent than the alpha-ketoheterocycles but had much slower on rates. By comparison of a series of alpha-ketoamide analogues, it is apparent that the there is a preference for binding of bulky hydrophobic substituents in the P' portion of the thrombin active site. Three of the inhibitors (MOL098, MOL144, and MOL174) were screened against a series of coagulation and anticoagulation enzymes and found to be selective for inhibition of the coagulation enzymes. Two of the inhibitors were tested in in vitro models of intestinal absorption and found to have low absorption potential. The compounds were then tested in vivo in both rats and primates, and one of them (MOL144) was approximately 25% absorbed in both species. This study has delineated the synthesis of constrained dipeptide beta-strand mimetics and validated the potential for compounds of this type as potent thrombin inhibitors and possible drug leads.     

Design,synthesis, evaluation,and molecular modeling studies of indolyl oxoacetamides as potential pancreatic lipase inhibitors

A series of indolyl oxoacetamide analogs was synthesized, characterized, and evaluated for their pancreatic lipase inhibitory activity using porcine pancreatic lipase (type II) and 4-nitrophenyl butyrate. Compound 8d exhibited a potent inhibition, with an IC₅₀ value of 4.53 µM, followed by 8c (IC₅₀ = 5.12 µM), compared with the standard drug, orlistat (IC₅₀ = 0.99 µM). Furthermore, analogs 8c and 8d exhibited a reversible competitive inhibition, similar to orlistat. Molecular docking studies of the compounds 7a–f and 8a – f were in agreement with the in vitro results, wherein 8d exhibited a potential MolDock score of −163.052 kcal/mol. A 10-ns molecular dynamics simulation of 8d complexed with pancreatic lipase confirmed the role of π–π stacking and π–cation interactions with the lid domain and Arg 256, respectively, in stabilizing the ligand at the active site (maximum observed root mean square deviation ≈ 2 Å). The present study led to the identification of novel indolyl oxoacetamides ( 8a – d ) as potential pancreatic lipase inhibitory leads that might further result in enhanced potency through lead optimization.     

Design, synthesis, and crystal structure of hydroxyethyl secondary amine-based peptidomimetic inhibitors of human beta-secretase

The design and synthesis of a novel series of potent and cell permeable peptidomimetic inhibitors of the human beta-secretase (BACE) are described. These inhibitors feature a hydroxyethyl secondary amine isostere and a novel aromatic ring replacement for the C-terminus. The crystal structure of BACE in complex with this hydroxyethyl secondary amine isostere inhibitor is also presented.     

2-氨基噻唑衍生物的设计、合成及对细胞凋亡的抑制活性

目的研究2-氨基噻唑衍生物对神经细胞凋亡的抑制作用和构效关系。方法以PFT-α为先导物,设计并合成出相应的2-氨基噻唑衍生物,利用MTT法和FCM法测定其对由过氧化氢诱导产生的PC12细胞凋亡的抑制作用,利用Cerius²的QSAR⁺模块,求出其QSAR方程。结果合成了11个新型含2-氨基噻唑母环的Schiff碱化合物II,利用IR,MS,¹H NMR,¹³C NMR等法对上述化合物进行表征。细胞实验结果表明,2-氨基噻唑衍生物对PC12细胞具有一定的保护作用并对由过氧化氢诱导的PC12细胞凋亡具有一定的抑制作用。优化QSAR方程为Activity＝6.947 68-0.088 72דLUMO”-0.043 018דAlogp98”-0.128 752דRad0fGration”＋0.018 246דDipole-mag”,上述方程的相关统计参数如下, r²=0.970, F-test=49.149,r=0.985,Lse=0.001。结论2-氨基噻唑衍生物对由过氧化氢诱导的PC12细胞凋亡具有较为明显的抑制作用,部分化合物如I-6,I-9和II-6对于PC12细胞具有细胞保护和细胞凋亡抑制双重活性。QSAR方程提示降低化合物的旋转半径以及化合物最低空轨道的能量有利于提高化合物的活性。     

Structure-based design, synthesis, and structure-activity relationship studies of novel non-nucleoside adenosine deaminase inhibitors

We disclose herein optimization efforts around the novel, highly potent non-nucleoside adenosine deaminase (ADA) inhibitor, 1-[(R)-1-hydroxy-4-(6-(3-(1-methylbenzimidazol-2-yl)propionylamino)indol-1-yl)-2-butyl]imidazole-4-carboxamide 1 (K(i)= 7.7 nM), which we recently reported. Structure-based drug design (SBDD) utilizing the crystal structure of the 1/ADA complex was performed in order to obtain structure-activity relationships (SAR) for this type of compound rationally and effectively. To utilize the newly formed hydrophobic space (F2), replacement of the benzimidazole ring of 1 with a n-propyl chain (4b) or a simple phenyl ring (4c) was tolerated in terms of binding activity, and the length of the methylene-spacer was shown to be optimal at two or three. Replacement of an amide with an ether as a linker was also well tolerated in terms of binding activity and moreover improved the oral absorption (6a and 6b). Finally, transformation of indol-1-yl to indol-3-yl resulted in discovery of a novel highly potent and orally bioavailable ADA inhibitor, 1-[(R)-4-(5-(3-(4-chlorophenyl)propoxy)-1-methylindol-3-yl)-1-hydroxy-2-butyl]imidazole-4-carboxamide 8c.     

Structure-based design, synthesis, and structure-activity relationship studies of HIV-1 protease inhibitors incorporating phenyloxazolidinones

A series of new HIV-1 protease inhibitors with the hydroxyethylamine core and different phenyloxazolidinone P2 ligands were designed and synthesized. Variation of phenyl substitutions at the P2 and P2' moieties significantly affected the binding affinity and antiviral potency of the inhibitors. In general, compounds with 2- and 4-substituted phenyloxazolidinones at P2 exhibited lower binding affinities than 3-substituted analogues. Crystal structure analyses of ligand-enzyme complexes revealed different binding modes for 2- and 3-substituted P2 moieties in the protease S2 binding pocket, which may explain their different binding affinities. Several compounds with 3-substituted P2 moieties demonstrated picomolar binding affinity and low nanomolar antiviral potency against patient-derived viruses from HIV-1 clades A, B, and C, and most retained potency against drug-resistant viruses. Further optimization of these compounds using structure-based design may lead to the development of novel protease inhibitors with improved activity against drug-resistant strains of HIV-1.     

Design and synthesis of novel 6,7-imidazotetrahydroquinoline inhibitors of thymidylate synthase using iterative protein crystal structure analysis.

Antifolate inhibitors of thymidylate synthase (TS) have primarily been based on the structure of folic acid. This paper describes the identification and development of novel 6,7-imidazotetrahydroquinoline TS inhibitors by iterative ligand design, synthesis, and crystallographic analysis of protein-inhibitor complexes. Beginning with a high-resolution crystal structure of E. coli TS (TS, EC 2.1.1.45), an imidazotetrahydroquinoline inhibitor was designed de novo to occupy the folate binding pocket. Structural modifications of the initial compound 1h (Ki approximately 5 microM human/E. coli TS) were then made on the basis of feedback from additional cocrystal structures and activity data. An amino group in the 2-position of the imidazole was found to increase the potency of the series by 1-2 orders of magnitude. Other substitutions on the imidazole ring (1-CH3, 2-CH3, 2-NHCH3, 2-SCH3) generally led to weaker inhibition. Additional improvements in activity were obtained by modification of the substituents on the tetrahydroquinoline nitrogen, bringing the Ki of three of the compounds below 15 nM against the human TS enzyme. The compounds were tested for cytotoxicity and were shown to inhibit the growth of three tumor cell lines in vitro.     

1-Thioangelicin: crystal structure, computer-aided studies and photobiological activity

1-Thioangelicin is a furocoumarin analog synthesized to investigate the role of the substitution of sulfur for oxygen in the parent compound angelicin. The compound was examined by X-ray diffraction, and its interaction with DNA, both in the dark and by UVA irradiation, studied by means of linear flow dichroism, chromatography and (1)H NMR. Further insight into the steric and electronic features of 1-thioangelicin has been reached through theoretical calculations, including molecular mechanics optimization, docking studies and frontier molecular orbital investigations. The experimental data indicate that thioangelicin is able to intercalate in the DNA helix and subsequent irradiation yields a cis-syn adduct, in agreement with theoretical calculations within the lower/higher singly occupied molecular orbital formalism. Antiproliferative activity has been assessed on Balb/c 3T3 cultured cells.     

Design,synthesis, crystal structure,bioactivity, and molecular docking studies of novel sulfonylamidine-derived neonicotinoid analogs

Two novel series of sulfonylamidine-derived neonicotinoid analogues were designed and synthesized via a Cu-catalyzed one pot reaction. The structures of the target compounds were characterized by ¹H-NMR, ¹³C-NMR, HR-MS and the single-crystal structure of 14k was further determined by X-ray diffraction crystallography. In preliminary bioassays, many of the target compounds exhibited significant activity against Tetranychus cinnabarinus (carmine spider mite) and Brevicoryne brassicae (cabbage aphid). Some structural features important for potency were observed, and a model of the ligand–receptor complex was also generated with a molecular docking study using representative active analogues. The molecular binding mode observed at the active site of the nicotinic acetylcholine receptor model should provide useful information for future structure-based design of novel sulfonylamidine-derived neonicotinoid analogues.     

Antimalarial drug discovery: screening of Brazilian medicinal plants and purified compounds

Background: Malaria is the most important parasitic disease and its control depends on specific chemotherapy, now complicated by Plasmodium falciparum that has become resistant to most commonly available antimalarials. Treatment of the disease requires quinine or drug combinations of artemisinin derivatives and other antimalarials. Further drug resistance is expected. New active compounds need to be discovered. Objective/method: To find new antimalarials from medicinal and randomly collected plants, crude extracts are screened against P. falciparum in cultures and in malaria animal models, following bioassays of purified fractions, and cytotoxicity tests. Conclusion: For antimalarial research, screening medicinal plants is more efficient than screening randomly chosen plants. Biomonitored fractionation allows selection of new active molecules identified as potential antimalarials in multidisciplinary projects in Brazil; no new molecule is available for human testing. The advantages of projects based on ethnopharmacology are discussed.     

HCMV蛋白酶抑制剂的研究(Ⅱ)杂环类抑制剂的设计与合成

目的 人巨细胞病毒（HCMV）是一种普遍存在的机会病原体。HCMV蛋白酶在装配蛋白产生和病毒壳体成熟中具有重要作用，抑制基作用可产生抗疱疹病毒药物。对杂环类HCMV蛋白酶抑制剂进行研究。方法 根据HCMV蛋白酶和拟肽类抑制剂复合物的晶体结构数据，借助计算机辅助药物设计手段，运用Docking(分子对接）技术，从MDDR库中筛选挑出35个预计可能与HCMV蛋白酶相互较好结合的杂环化合物。首先选择目标物2-（香豆素-3-基）-5-氟-4H-3,1-苯并恶嗪-4-酮（I）和3-（2-羟基-4-甲基-苯甲酰基）-2-（4-甲氧基-苯基）-2，3-二氢-异吲哚-1-酮（Ⅱ）为合成和检验对象。结果 设计并完成了目标物I和Ⅱ的合成路线。结论 所得产物的结构经MS，IR，^1H-NMR及元素分析确证与目标物I和Ⅱ相符。     

Pyrazolobenzotriazinone derivatives as COX inhibitors: synthesis, biological activity, and molecular-modeling studies

Pyrazolylbenzotriazinones are endowed with a structural analogy with the COX-2 selective inhibitor celecoxib. Considering that our research group has long been interested in the 3-pyrazolyl-substituted benzotriazinones as anti-inflammatory agents, six new pyrazolylbenzotriazinone derivatives 16a-c and 18a-c have been prepared by reacting the opportune ethyl 5-(2-aminobenzamido)-1-(pyridin-2-yl)-1H-pyrazole-4-carboxylate or 5-(2-aminobenzamido)-1-(pyridin-2-yl)-1H-pyrazole-4-carboxyic acid with sodium nitrite in glacial acetic acid. The biological studies revealed a good pharmacological profile for some pyrazolylbenzotriazinones and, in the case of the ethyl 5-(4-oxo-1,2,3-benzotriazin-3(4H)-yl)-1-pyridin-2-yl-1H-pyrazole-4-carboxylate, a good COX-1/COX-2 selectivity. Molecular modeling studies confirmed the obtained biological results.