piperidines and febrifugine

The quinazolinone-containing 2,3-disubstituted piperidines febrifugine and isofebrifugine have been the subject of significant research efforts since their occurrence in Dichroa febrifuga and their anti-malarial actions were first described in the late 1940s. Subsequently they have also been shown to be present in other plants belonging to the hydrangea family and various analogues of febrifugine have been prepared in attempts to tune biological properties. The most notable analogue is termed halofuginone and a substantial body of work now demonstrates that this compound possesses potent human disease relevant activities. This review focuses on the literature associated with efforts dedicated towards uncovering the structures of febrifugine and isofebrifugine, the development of practical methods for their synthesis and the syntheses of structural analogues.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Antimalarials; Cyclization; Cycloaddition Reaction; Humans; Piperidines; Plasmodium falciparum; Quinazolines; Quinazolinones; Stereoisomerism

The trans-2,3-disubstituted piperidine, quinazolinone-containing natural product febrifugine (also known as dichroine B) and its synthetic analogue, halofuginone, possess antimalarial activity. More recently studies have also shown that halofuginone acts as an agent capable of reducing fibrosis, an indication with clinical relevance for several disease states. This review summarizes historical isolation studies and the chemistry performed which culminated in the correct structural elucidation of naturally occurring febrifugine and its isomer isofebrifugine. It also includes the range of febrifugine analogues prepared for antimalarial evaluation, including halofuginone. Finally, a section detailing current opinion in the field of halofuginone's human biology is included.

Topics: Antimalarials; Humans; Molecular Structure; Parasitic Sensitivity Tests; Piperidines; Plasmodium; Quinazolines; Quinazolinones; Structure-Activity Relationship

Two antimalaria alkaloids, febrifugine and isofebrifugine, were successfully separated from total alkaloids of Dichroa febrifuga roots by one-step preparative countercurrent chromatography with a selected biphasic solvent system. The selected biphasic solvent system was composed of chloroform: methanol: water (2:1:1, v/v) according to partition performance of the two target components. Selection of biphasic solvent system was conducted by high performance liquid chromatography combined with high performance thin layer chromatography, which greatly assisted the screening procedure for biphasic solvent system. Totally, 50 mg of total alkaloid was separated by one-step preparative countercurrent chromatography, yielding 12 mg of febrifugine and 9 mg of isofebrifugine with more than 98.0% purity, respectively.

Topics: Alkaloids; Countercurrent Distribution; Hydrangea; Piperidines; Plant Extracts; Plant Roots; Quinazolines

In this study, 105 broiler chickens were fed with dietary feeds containing different contents of Dichroae Radix extract for 10 consecutive days. Then the residue depletions of its main alkaloids (febrifugine and isofebrifugine) in muscle, kidney and liver samples at different withdrawal times were determined by an ultra-performance liquid chromatography method. Results showed that the 2 alkaloids were mainly at tissue-bound formation. At withdrawal period of 0 d, their concentrations in all samples were high but decreased rapidly after 1 day of cessation (35-91%). After 5 to 7 days of cessation, their residues in muscle and kidney were not detectable, and after at least 10 days of cessation they were not detectable in liver. These results indicated that an appropriate withdrawal time for Dichroae Radix preparation was required if it is licensed as a new drug, and the best target tissue for monitoring its residue was liver.

Topics: Animals; Chickens; Drug Residues; Liver; Meat; Piperidines; Quinazolines

Febrifugine hydrochloride (FFH) has strong pharmacological antimalarial effect. However, compared with oral administration, the efficacy of intravenous administration is significantly reduced. In this study, we prepared conventional liposomes and PEGylated liposomes to improve the efficacy of its intravenous injection. Both liposome formulations were prepared using a modified ethanol injection method. Their mean particle sizes were 126.23 and 114.93 nm, mean zeta potentials were -6.25 and -26.33 mV, and entrapment efficiencies (EE) were 89.43 and 96.42%, respectively. The

Topics: Animals; Liposomes; Mice; Particle Size; Piperidines; Polyethylene Glycols; Quinazolines

Gastric cancer (GC) is one of the most common fatal cancers among gastrointestinal malignancies. At present, the treatment of gastric cancer involves a combination of surgery and chemotherapy. Isofebrifugine (IFE) is an alkaloid with many biological properties. In this study, results from MTT, scratch and invasion assays showed that IFE significantly inhibited the proliferation, migration and invasion of SGC7901 gastric cancer cells. Through RT-PCR and Western blot experiments, it was revealed that IFE significantly inhibited the mRNA and protein expressions of MMP-2, MMP-9 and SDF-1 which are closely related to cancer invasion and metastasis. Thus, IFE possesses anti-gastric cancer properties.

Topics: Cell Line, Tumor; Cell Movement; Cell Proliferation; Chemokine CXCL12; Gene Expression Regulation, Neoplastic; Humans; Matrix Metalloproteinase 2; Matrix Metalloproteinase 9; Neoplasm Invasiveness; Piperidines; Quinazolines; RNA, Messenger; Stomach Neoplasms

A quantitative nuclear magnetic resonance method(qNMR) was established for determination of the absolute content of febrifugine. Proton nuclear magnetic resonance spectroscopy of febrifugine was obtained in DMSO-d₆ with hydroquinone as the internal standard substance on a Bruker Ascend 600 MHz superconducting nuclear resonance spectrometer at 298 K. The specific parameters were as follows: the observing frequency was 600 MHz,spectra width was 7 211 Hz, pulse width was 9.70 μs, pulse sequence was zg30,scan times was 32 and relaxation time was 2 s. The proton signal peaked at δ 7.71 for febrifugine and δ 6.55 for hydroquinone were selected as the quantification peaks. Linear regression of quantitative peak area ratio of febrifugine-hydroquinone versus their mass ratio yielded a correlation coefficient of 0.999 6 and a regression equation of

Topics: Magnetic Resonance Spectroscopy; Piperidines; Protons; Quinazolines

To develop the HPLC method for simultaneous determination of febrifugine and isofebrifugine in Dichroa febrifuga root, and on the basis of this, the feasibility of quantitative analysis of multi-component by a single-marker (QAMS) model for the determination of the two alkaloids was investigated. The chromatographic separation was performed on an octadecyl bonded silica gel column with mixed solvent consisting of acetonitrile-water-glacial acetic acid-triethylamine (9∶91∶0.36∶0.745) as mobile phase at a flow rate of 1.0 mL•min⁻¹. The detection wavelength was set at 225 nm, and the column temperature was set at 30 ℃. The linear range of febrifugine and isofebrifugine were 10.7-426 ng and 10.6-424 ng, respectively. Their average recovery were 98.33% (RSD 2.7%) and 100.4% (RSD 1.8%), respectively. On the basis of this established method, febrifugine was used as the internal reference substance to calculate the relative correction factors (RCF) and the relative retention values (RRV) of isofebrifugine to febrifugine. Through a series of methodology evaluations, the two alkaloids were simultaneously assayed only by quantitative determination of febrifugine. This result played the part of demonstration role for the application of QAMS model in the determination of isomers.

Topics: Chromatography, High Pressure Liquid; Hydrangea; Piperidines; Plant Roots; Quinazolines

To investigate the stability and degradation kinetics of febrifugine. The results showed that within 24 hours, febrifugine content was decreased by only 1% in mobile phase solvent, but its content was decreased to be 90% of the initial content in the water, methanol, 50% methanol and 10% acetonitrile solution. When the pH value of the solution was between 3 and 7, the retention rate of febrifugine in 24 hours was over 98%, but its content was decreased by about 12% in alkaline solution (pH 9.0). The higher the temperature, the worse the stability of febrifugine. At 40-80 ℃, the content of febrifugine was decreased to be 60% of its initial content in 10 hours, but the content was decreased by only 5% in 10 h at 20 ℃.However, no matter 40 ℃or 60 ℃, febrifugine was mainly transformed into isofebrifugine, and the total content of febrifugine and isofebrifugine was equal to their initial total content in 10 hours, while incase of 80 ℃, the total content was decreased to be 83.33% in 10 h, which suggested that the structure of febrifugine was absolutely changed, not just isomerized to be isofebrigugine at high temperature. Light had a significant impact on the stability of febrifugine. Under bright light, the content of febrifugine was reduced by about 23% in 108 h, but it only decreased by about 10% in the natural light or darkness. In artificial gastric fluid (pH 1.4) and artificial intestinal fluid (pH 6.8), the content of febrifugine was decreased by less than 5% in 10 h. After storage at high temperature(60 ℃), high humidity [(75±1)%] and strong light (3 000 lx) conditions for 10 d, the content of solid febrifugine was decreased by 0.27%, 7.6% and 5.39%, respectively. The degradation of febrifugine basically complied with the first-order reaction kinetic process in the following conditions: in water, methanol, 50%methanol and 10% acetonitrile solvents, alkaline solution (pH>7), different light intensity and different temperatures (20,40 ℃). Therefore, no matter the isolation and purification of febrifugine or the production of the related preparations, it should be done fast in the acidic solution, low temperature and dark conditions, while the febrifugine solid should be kept in dry and dark conditions.

Topics: Drug Stability; Hydrogen-Ion Concentration; Kinetics; Piperidines; Quinazolines; Temperature

Malaria is an endemic disease caused by the protozoan parasite Plasomodium falciparum. Febrifugine analogues are natural compound obtained from the traditional Chinese herbs have shown significant antimalarial and anticancerous efficacy in experimental model. Development of resistance against the existing antimalarial drug has alarmed the scientific innovators to find a potential antimalarial molecule which can be further used by endemic countries for the elimination of this disease. In this study, structure-based virtual screening and molecular dynamics (MD) base approaches were used to generate potential antimalarial compound against plasmepsin II and prolyl-tRNA synthetase of Plasmodium. Here, we have docked series of febrifugine analogues (n = 11,395) against plasmepsin II in three different docking modes and then it was compared with previously reported target prolyl-tRNA synthetase. Extra precision docking resulted into 235 ligands having better docking score were subject for QikProp analysis. Better ligands (n = 39) obtained from QikProp analysis were subject for ADMET prediction and docking protocol validation through the estimation of receiver operator characteristics. In the later stage, 24 ligands obtained from ADMET study were subject for the estimation of binding energy through MM-GBSA and same were also docked against prolyl-tRNA synthetase to get compounds with dual inhibitor role. Finally, MD simulation and 2D fingerprint MACCS study of two best ligands have shown significant interaction with plasmepsin II and homology against known active ligand with noteworthy MACCS index, respectively. This study concludes that FA12 could be potential drug candidate to fight against Plasmodium falciparum parasites.

Topics: Amino Acyl-tRNA Synthetases; Antimalarials; Aspartic Acid Endopeptidases; Drug Design; Drug Evaluation, Preclinical; Humans; Molecular Conformation; Molecular Dynamics Simulation; Molecular Structure; Piperidines; Plasmodium falciparum; Protein Binding; Protozoan Proteins; Quinazolines; Structure-Activity Relationship

Visceral leishmaniasis affects people from 70 countries worldwide, mostly from Indian, African and south American continent. The increasing resistance to antimonial, miltefosine and frequent toxicity of amphotericin B drives an urgent need to develop an antileishmanial drug with excellent efficacy and safety profile. In this study we have docked series of febrifugine analogues (n = 8813) against trypanothione reductase in three sequential docking modes. Extra precision docking resulted into 108 ligands showing better docking score as compared to two reference ligand. Furthermore, 108 febrifugine analogues and reference inhibitor clomipramine were subjected to ADMET, QikProp and molecular mechanics, the generalized born model and solvent accessibility study to ensure the toxicity caused by compounds and binding-free energy, respectively. Two best ligands (FFG7 and FFG2) qualifying above screening parameters were further subjected to molecular dynamics simulation. Conducting these studies, here we confirmed that 6-chloro-3-[3-(3-hydroxy-2-piperidyl)-2-oxo-propyl]-7-(4-pyridyl) quinazolin-4-one can be potential drug candidate to fight against Leishmania donovani parasites.

Topics: Antiprotozoal Agents; Binding Sites; Drug Design; Enzyme Inhibitors; Leishmania donovani; Ligands; Models, Molecular; Molecular Conformation; Molecular Docking Simulation; Molecular Dynamics Simulation; NADH, NADPH Oxidoreductases; Piperidines; Protein Binding; Protein Multimerization; Quinazolines; ROC Curve; Structure-Activity Relationship

The total syntheses of two fluorinated alkaloids, 6-(R)-fluoroswainsonine and 5-(R)-fluorofebrifugine, are described. Both encompass (4aS,7R,8aR)-7-fluoro-5-tosylhexahydro-4H-[1,3]dioxino[5,4-b]pyridine as a key synthon which is obtained through a further optimized palladium-catalyzed aminofluorination of alkenes with high diastereoselectivity. 6-(R)-Fluoroswainsonine is synthesized from the key synthon in 14 steps, and 5-(R)-fluorofebrifugine requires a sequential 15-step transformation.

Topics: Alkaloids; Alkenes; Catalysis; Molecular Structure; Palladium; Piperidines; Pyridines; Quinazolines; Stereoisomerism; Swainsonine

The emergence of drug resistance is a major limitation of current antimalarials. The discovery of new druggable targets and pathways including those that are critical for multiple life cycle stages of the malaria parasite is a major goal for developing next-generation antimalarial drugs. Using an integrated chemogenomics approach that combined drug resistance selection, whole-genome sequencing, and an orthogonal yeast model, we demonstrate that the cytoplasmic prolyl-tRNA (transfer RNA) synthetase (PfcPRS) of the malaria parasite Plasmodium falciparum is a biochemical and functional target of febrifugine and its synthetic derivative halofuginone. Febrifugine is the active principle of a traditional Chinese herbal remedy for malaria. We show that treatment with febrifugine derivatives activated the amino acid starvation response in both P. falciparum and a transgenic yeast strain expressing PfcPRS. We further demonstrate in the Plasmodium berghei mouse model of malaria that halofuginol, a new halofuginone analog that we developed, is active against both liver and asexual blood stages of the malaria parasite. Halofuginol, unlike halofuginone and febrifugine, is well tolerated at efficacious doses and represents a promising lead for the development of dual-stage next-generation antimalarials.

Topics: Amino Acyl-tRNA Synthetases; Animals; Antimalarials; Computer-Aided Design; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Design; Drug Resistance; Enzyme Inhibitors; Erythrocytes; Liver; Malaria, Falciparum; Mice; Models, Molecular; Molecular Structure; Molecular Targeted Therapy; Piperidines; Plasmodium falciparum; Protozoan Proteins; Quinazolines; Quinazolinones; Structure-Activity Relationship; Time Factors

Febrifugine, a quinazoline alkaloid isolated from Dichroa febrifuga roots, shows powerful antimalarial activity against Plasmodium falciparum. Although the use of ferifugine as an antimalarial drug has been precluded because of its severe side effects, its potent antimalarial activity has stimulated medicinal chemists to pursue its derivatives instead, which may provide valuable leads for novel antimalarial drugs. In the present study, we synthesized new derivatives of febrifugine and evaluated their in vitro and in vivo antimalarial activities to develop antimalarials that are more effective and safer. As a result, we proposed tetrahydroquinazoline-type derivative as a safe and effective antimalarial candidate.

Topics: Animals; Antimalarials; Magnetic Resonance Spectroscopy; Piperidines; Plasmodium falciparum; Quinazolines; Spectrometry, Mass, Fast Atom Bombardment

Topics: Adult; Female; Foodborne Diseases; Humans; Hydrangea; Male; Middle Aged; Piperidines; Quinazolines; Stereoisomerism

Aminoacyl-tRNA synthetases (aaRSs) drive protein translation in cells and hence these are essential enzymes across life. Inhibition of these enzymes can halt growth of an organism by stalling protein translation. Therefore, small molecule targeting of aaRS active sites is an attractive avenue from the perspective of developing anti-infectives. Febrifugine and its derivatives like halofuginone (HF) are known to inhibit prolyl-tRNA synthetase of malaria parasite Plasmodium falciparum. Here, we present functional and crystallographic data on P. falciparum prolyl-tRNA synthetase (PfPRS). Using immunofluorescence data, we show that PfPRS is exclusively resident in the parasite cytoplasm within asexual blood stage parasites. The inhibitor HF interacts strongly with PfPRS in a non-competitive binding mode in presence or absence of ATP analog. Intriguingly, the two monomers that constitute dimeric PfPRS display significantly different conformations in their active site regions. The structural analyses presented here provide a framework for development of febrifugine derivatives that can seed development of new anti-malarials.

Topics: Amino Acyl-tRNA Synthetases; Antimalarials; Catalytic Domain; Crystallography, X-Ray; Enzyme Inhibitors; Malaria, Falciparum; Piperidines; Plasmodium falciparum; Protozoan Proteins; Quinazolines

A series of febrifugine analogues were designed and synthesized. Antimalarial activity evaluation of the synthetic compounds indicated that these derivatives had a strong inhibition against both chloroquine-sensitive and -resistant Plasmodium falciparum parasites. Many of them were found to be more active than febrifugine hydrochloride. The tested analogues had also a significant cytotoxicity against four cancer cell lines (KB, MCF7, LU1 and HepG2). Among the synthetic analogues, two compounds 17b and 17h displayed a moderate cytotoxicity while they exhibited a remarkable antimalarial activity.

Topics: Antimalarials; Antineoplastic Agents; Cell Line, Tumor; Humans; Piperidines; Plasmodium falciparum; Quinazolines

Febrifugine is the active component of the Chinese herb Chang Shan (Dichroa febrifuga Lour.), which has been used for treating malaria-induced fever for about 2,000 years. Halofuginone (HF), the halogenated derivative of febrifugine, has been tested in clinical trials for potential therapeutic applications in cancer and fibrotic disease. Recently, HF was reported to inhibit T(H)17 cell differentiation by activating the amino acid response pathway, through inhibiting human prolyl-transfer RNA synthetase (ProRS) to cause intracellular accumulation of uncharged tRNA. Curiously, inhibition requires the presence of unhydrolysed ATP. Here we report an unusual 2.0 Å structure showing that ATP directly locks onto and orients two parts of HF onto human ProRS, so that one part of HF mimics bound proline and the other mimics the 3' end of bound tRNA. Thus, HF is a new type of ATP-dependent inhibitor that simultaneously occupies two different substrate binding sites on ProRS. Moreover, our structure indicates a possible similar mechanism of action for febrifugine in malaria treatment. Finally, the elucidation here of a two-site modular targeting activity of HF raises the possibility that substrate-directed capture of similar inhibitors might be a general mechanism that could be applied to other synthetases.

Topics: Adenosine Triphosphate; Amino Acyl-tRNA Synthetases; Antimalarials; Binding Sites; Crystallography, X-Ray; Herbal Medicine; Humans; Hydrogen Bonding; Hydrophobic and Hydrophilic Interactions; Ligands; Medicine, Chinese Traditional; Models, Molecular; Piperidines; Proline; Quinazolines; Quinazolinones; RNA, Transfer

Febrifugine is an alkaloid isolated from Dichroa febrifuga Lour as the active component against Plasmodium falciparum, but exhibits toxic side effects. In this study novel febrifugine analogues were designed and efficiently synthesized. New compounds underwent efficacy and toxicity evaluation. Some compounds are much less toxic than the natural product febrifugine and existing antimalarial drugs and are expected to possess wide therapeutic windows. In Aotus monkeys infected with the chloroquine resistant FVO strain of P. falciparum, one interesting compound possesses a 50% curative dose of 2mg/kg/day and a 100% curative dose of 8 mg/kg/day. These compounds, as well as the underlying design rationale, may find usefulness in the discovery and development of new antimalarial drugs.

Topics: Animals; Antimalarials; Aotus trivirgatus; Drug Evaluation, Preclinical; Malaria; Piperidines; Plasmodium falciparum; Quinazolines

Febrifugine, the bioactive constituent of one of the 50 fundamental herbs of traditional Chinese medicine, has been characterized for its therapeutic activity, though its molecular target has remained unknown. Febrifugine derivatives have been used to treat malaria, cancer, fibrosis and inflammatory disease. We recently demonstrated that halofuginone (HF), a widely studied derivative of febrifugine, inhibits the development of T(H)17-driven autoimmunity in a mouse model of multiple sclerosis by activating the amino acid response (AAR) pathway. Here we show that HF binds glutamyl-prolyl-tRNA synthetase (EPRS), inhibiting prolyl-tRNA synthetase activity; this inhibition is reversed by the addition of exogenous proline or EPRS. We further show that inhibition of EPRS underlies the broad bioactivities of this family of natural product derivatives. This work both explains the molecular mechanism of a promising family of therapeutics and highlights the AAR pathway as an important drug target for promoting inflammatory resolution.

Topics: Amino Acyl-tRNA Synthetases; Animals; Cell Differentiation; Dose-Response Relationship, Drug; Enzyme Inhibitors; Humans; Mice; Mice, Inbred C57BL; Piperidines; Quinazolines; Quinazolinones; Structure-Activity Relationship; Th17 Cells

The asymmetric dihydroxylation of amino-functionalized vinyl sulfone 19 has been used for the 3-step preparation of 3-hydroxylpiperidine 24 in 86% enantiomeric excess. This enantiomerically enriched building block was used then to synthesize the naturally occurring antimalarial alkaloid febrifugine 1 and its antiangiogenic analogue, halofuginone 3.

Topics: Catalysis; Hydroxylation; Molecular Structure; Piperidines; Quinazolines; Quinazolinones; Stereoisomerism; Sulfones

Febrifugine and its derivatives including halofuginone which possess very high activity against malaria were prepared synthetically from easily available starting material, 3-hydroxy picoline, and using simple reaction conditions. Synthesis of 2-amino-5, 6-methylenedioxy benzoic acid, (which is an intermediate for the process) is described. The selectivity enhancement in nitration of 3, 4-methylenedioxybenzaldehyde towards 6-nitro isomer was done with the help of surfactant. The antimalarial activity of synthesized compounds was determined by using in vitro assays against chloroquine sensitive (D6), chloroquine resistant (W2) Plasmodium falciparum strains for susceptibility and two mammalian cell lines (neuronal cell line NG108 and macrophage cell line J774) for cytotoxicity. The IC(50)s of halofuginone was observed to be the best among the synthesized derivatives of febrifugine.

Topics: Animals; Antimalarials; Benzoates; Cell Line; Piperidines; Plasmodium falciparum; Quinazolines; Quinazolinones

Febrifugine is an alkaloid isolated from Dichroa febrifuga Lour as the active component against Plasmodium falciparum. Adverse side effects have precluded febrifugine as a potential clinical drug. In this study novel febrifugine analogues were designed and synthesized. Lower toxicity was achieved by reducing or eliminating the tendency of forming chemically reactive and toxic intermediates and metabolites. Synthesized compounds were evaluated for acute toxicity and in vitro and in vivo antimalarial efficacy. Some compounds are much less toxic than the natural product febrifugine and existing antimalarial drug chloroquine and are expected to possess wide therapeutic windows. These compounds, as well as the underlying design rationale, may find usefulness in the discovery and development of new antimalarial drugs.

Topics: Animals; Antimalarials; Drug Evaluation, Preclinical; Hydrangeaceae; Malaria; Mice; Molecular Structure; Parasitic Sensitivity Tests; Piperidines; Plasmodium falciparum; Quinazolines; Structure-Activity Relationship

Two complementary strategies for the synthesis of febrifugine are detailed based on previously developed chemoenzymatic approaches to the 3-hydroxypiperidine skeleton. The introduction of the quinazolone-containing side chain in both strategies was based on an N-acyliminium ion-mediated coupling reaction.

Topics: Catalysis; Piperidines; Quinazolines; Stereoisomerism; Substrate Specificity

Charge neutral TpMo(CO)(2)(5-acyloxy-eta(3)-pyranyl) and TpMo(CO)(2)(5-acyloxy-eta(3)-pyridinyl) scaffolds undergo a novel intermolecular "homo-S(N)2'-like" reaction with a variety of carbon nucleophiles. Combined with an annulative demetalation, the homo-S(N)2'-like substitution/annulative demetalation sequence rapidly generates 2,7-dioxabicyclo[4.3.0]nonane and 2-aza-7-oxabicyclo[4.3.0]nonane frameworks in good to excellent yields with high enantiopurity. An enantiocontrolled total synthesis of the antimalarial alkaloid (+)-isofebrifugine was achieved utilizing this reaction cascade.

Topics: Antimalarials; Molybdenum; Organometallic Compounds; Piperidines; Pyridines; Quinazolines; Stereoisomerism; Substrate Specificity

Febrifugine is an alkaloid with potent antimalarial activity isolated from Dichroa febrifuga and Hydrangea umbellate, and it exists naturally with its diastereomeric component, isofebrifugine. Here we report the differentiation of diastereomeric synthetic precursors of isofebrifugine (1, cis) and febrifugine (2, trans) and a structurally similar model diastereomeric pair without a halogen substituent (3 and 4) by electrospray ionization (ESI) tandem mass spectrometry. Compounds 1-4 contain a tert-butoxycarbonyl (BOC) substituent, and the collision-induced dissociation (CID) spectra of the [M+H](+), [M+Na](+) and [M+Li](+) ions of 1-4 include the expected product ions corresponding to the loss of C(4)H(8) (isobutene) and of C(5)H(8)O(2) (BOC-H). Loss of C(5)H(8)O(2) is dominant in cis isomers (1 and 3) and/or loss of C(4)H(8) ions is dominant in trans isomers (2 and 4). The decomposition of [M+H](+) ions shows stereoselectivity in the formation of the [M+H-(BOC-H)-C(3)H(5)OBr](+) and [M+H-(BOC-H)-C(6)H(5)CH(2)OH](+) ions. The [M+Cat](+) ions (where Cat = Na or Li) additionally show loss of NaBr and HBr from [M+Cat-(BOC-H)](+), and these product ions are constantly more abundant in cis isomers than in trans isomers. The stereoselectivity for the product ion corresponding to the loss of [(BOC-H)+C(3)H(5)OBr] from [M+H](+) ions differs from that from [M+Cat](+) ions.

Topics: Antimalarials; Hydrangea; Isomerism; Molecular Structure; Piperidines; Plants, Medicinal; Quinazolines; Spectrometry, Mass, Electrospray Ionization; Tandem Mass Spectrometry

The stereoselective syntheses of 2-substituted and 2,6-disubstituted 3-hydroxypiperidine alkaloids, (+)-isofebrifugine and (-)-sedacryptine, from a common, functionalized nonracemic bicyclic building block are achieved, demonstrating the flexibilty of the approach.

Topics: Alkaloids; Piperidines; Piperidones; Quinazolines; Stereoisomerism

Parasitemia patterns, survival and cytokine levels of Plasmodium berghei NK65-infected BALB/c mice, treated orally with the alkaloidal mixture of febrifugine and isofebrifugine at a dose of 1 mg/kg twice a day for 4 consecutive days were monitored. Whereas the untreated mice showed a progressive increase in parasitemia and ultimate death, the alkaloid mixture-treated group showed a transient suppression of parasitemia during the course of treatment. However, the parasitemia increased on discontinuation of treatment, leading to earlier death of mice in the treated group than in the infected but untreated controls. Mice in the infected but untreated group displayed a significant elevation in serum IFN-gammay levels during the first week post-infection (pI) and from Day 14 pI, relative to the levels in the uninfected controls. In contrast, although mice in the alkaloid mixture-treated group displayed no significant elevation in serum IFN-gamma levels during the first week pI, they showed considerable levels on Day 14 pI. There were no significant differences in serum IL-4 levels among the groups. The titers of the parasite-specific IgG1, IgG2a, IgG2b and IgG3 were significantly elevated from Day 11 pI in both the treated and untreated groups. There was a significant difference in survival duration between the IFN-gamma-/- mutant and BALB/c mice. IFN-gamma-/- mutant mice showed a decrease in parasitemia levels while receiving medication, which was significantly lower than those of the treated BALB/c mice. The results of the present study suggest that although IFN-gamma is significant for protective immunity in mice with malaria infection, it may play an adverse role post-medication, causing earlier mortality of treated BALB/c mice.

Topics: Animals; Antibodies, Protozoan; Antigens, Protozoan; Antimalarials; Interferon-gamma; Interleukin-4; Malaria; Male; Mice; Mice, Inbred BALB C; Parasitemia; Piperidines; Plasmodium berghei; Quinazolines

Febrifugine is an alkaloid isolated from Dichroa febrifuga Lour as the active component against Plasmodium falciparum. Strong liver toxicity has precluded febrifugine as a potential clinical drug. In this study novel febrifugine analogues were designed and synthesized. Lower toxicity was achieved by reducing or eliminating the tendency of forming chemically reactive and toxic intermediates and metabolites. Synthesized compounds were evaluated in vitro against chloroquine sensitive (D6) and chloroquine resistant (W2) P. falciparum strains for efficacy and in freshly isolated rat hepatocytes for potential cytotoxicity. The IC(50)'s of the best compounds were superior to their parent compound febrifugine. Noticeably, these compounds were also over 100 times less toxic than febrifugine. These compounds, as well as the underlying design rationale, may find usefulness in the discovery and development of new antimalarial drugs.

Topics: Animals; Antimalarials; Drug Evaluation, Preclinical; Hepatocytes; Magnetic Resonance Spectroscopy; Piperidines; Plasmodium falciparum; Quinazolines; Rats

Febrifugine (1), a quinazoline alkaloid, isolated from Dichroa febrifuga roots, shows powerful antimalarial activity against Plasmodium falciparum. The use of 1 as an antimalarial drug has been precluded because of side effects, such as diarrhea, vomiting, and liver toxicity. However, the potent antimalarial activity of 1 has stimulated medicinal chemists to pursue compounds derived from 1, which may be valuable leads for novel drugs. In this study, we synthesized a new series of febrifugine derivatives formed by structural modifications at (i) the quinazoline ring, (ii) the linker, or (iii) the piperidine ring. Then, we evaluated their antimalarial activities. Thienopyrimidine analogue 15 exhibited a potent antimalarial activity and a high therapeutic selectivity both in vitro and in vivo, suggesting that 15 is a good antimalarial candidate.

Topics: Animals; Antimalarials; Cell Line; Malaria; Mice; Parasitic Sensitivity Tests; Piperidines; Plasmodium berghei; Plasmodium falciparum; Pyrimidinones; Quinazolines; Stereoisomerism; Structure-Activity Relationship; Thiophenes; Toxicity Tests, Acute

Febrifugine is the active principal isolated 50 years ago from the Chinese herb chang shan (Dichroa febrifuga Lour), which has been used as an antimalarial in Chinese traditional medicine for more than 2,000 years. However, intensive study of the properties of febrifugine has been hindered for decades due to its side effects. We report new findings on the effects of febrifugine analogs compared with those of febrifugine extracted from the dry roots of D. febrifuga. The properties of the extracted febrifugine were comparable to those obtained from the standard febrifugine provided by our collaborators. A febrifugine structure-based computer search of the Walter Reed Chemical Information System identified 10 analogs that inhibited parasite growth in vitro, with 50% inhibitory concentrations ranging from 0.141 to 290 ng/ml. The host macrophages (J744 cells) were 50 to 100 times less sensitive to the febrifugine analogs than the parasites. Neuronal (NG108) cells were even more insensitive to these drugs (selectivity indices, >1,000), indicating that a feasible therapeutic index for humans could be established. The analogs, particularly halofuginone, notably reduced parasitemias to undetectable levels and displayed curative effects in Plasmodium berghei-infected mice. Recrudescence of the parasites after treatment with the febrifugine analogs was the key factor that caused the death of most of the mice in groups receiving an effective dose. Subcutaneous treatments with the analogs did not cause irritation of the gastrointestinal tract when the animals were treated with doses within the antimalarial dose range. In summary, these analogs appear to be promising lead antimalarial compounds that require intensive study for optimization for further down-selection and development.

Topics: Animals; Antimalarials; Cell Line; Macrophages; Mice; Mice, Inbred ICR; Piperidines; Quinazolines

Racemic compound (1) of the antimalarial agents febrifugine (d-1) was synthesized using an stereoselective Michael reaction of an omega-amidoenone (5) which was prepared by the Wittig reaction of piperidinediol (7).

Topics: Antimalarials; Molecular Structure; Piperidines; Quinazolines

Topics: Antimalarials; Artemisia; Artemisinins; History, 20th Century; History, 21st Century; Humans; Hydrangea; Methaqualone; Piperidines; Plant Extracts; Quinazolines; Quinine; World War II

Cytokine and antibody production was investigated during the course of resolution of primary infection in Plasmodium yoelii 17XL-infected BALB/c mice treated with a mixture of febrifugine and isofebrifugine. The infected mice in an untreated control group showed a progressively increasing parasitemia, leading to mouse death. In contrast, infected mice given the mixture orally showed low parasitemia levels during administration. Following a transient increase in parasitemia in the bloodstream of the treated mice, no parasites could be detected by microscopic examination. Analysis of cytokines in plasma showed that the plasma IFN-gamma levels elevated significantly within the first week of infection in both groups. Furthermore, on day 20 the plasma IFN-gamma and IL-4 levels elevated significantly in the treated mice and the production of both cytokines was sustained until at least day 40. The production of both cytokines in the treated mice was coincident with a decrease in parasitemia. The production of parasite-specific antibodies in the course of P. yoelii 17XL infection was also monitored. In the drug-treated mice, the titers of parasite-specific IgG1, IgG2a, IgG2b and IgG3 elevated significantly from day 20; and the production of parasite-specific antibodies was coincident with a decrease in parasite numbers in the bloodstream.

Topics: Animals; Antibodies, Protozoan; Cytokines; Female; Hydrangea; Malaria; Mice; Mice, Inbred BALB C; Phytotherapy; Piperidines; Plant Leaves; Plasmodium yoelii; Quinazolines

The antimalarial activity of Hydrangea macrophylla var. Otaksa alkaloids was evaluated against Plasmodium yoelii 17XL, P. berghei NK65 and P. chabaudi AS in ICR mice. For trials in P. yoelii 17XL or P. chabaudi AS infections, mice were infected intraperitoneally with 10(5), 10(6) and 10(7) parasitized erythrocytes, respectively, and in P. berghei NK65 infections, mice were infected intraperitoneally with 10(3), 10(4) and 10(5) parasitized erythrocytes, respectively. Three days after injection, mice were orally given febrifugine and isofebrifugine mixture at 1 mg/kg in the treated group and 0.5% cremophor EL solution in the untreated, infected one, respectively, twice a day for 5 consecutive days. In P. yoelii 17XL infections, mice in all the non-treated controls died from 5 to 9 dpi with a gradual body weight loss and increasing parasitemias. In the treated groups, the mouse body weight gradually decreased after the end of administration but turned to increase in several days, and except one mouse in the group given 10(6) parasitized erythrocytes, other mice survived during the experiment. Mice given orally the mixture showed low parasitemia levels during administration. Following a transient recrudescence of malaria parasites in the bloodstream of treated mice, no parasites could be detected by a microscopic examination. In P. berghei NK65 infections, mice in all the non-treated controls died from 7 to 12 dpi with a gradual body weight loss and increasing parasitemias. In the treated groups, the body weight gradually decreased from 11 dpi and all mice died from 12 to 30 dpi. During a mixture administration all mice showed slight suppression of multiplication of malaria parasites. After the end of administration, however, malaria parasites increased in the bloodstream of the treated mice and all mice died. In P. chabaudi AS infections, there were two different patterns in the course of infection; lethal infection or recovery in both the non-treated control and treated groups. In the non-treated and treated groups, mice showed a gradual body weight loss. But the body weights of survivals in both groups turned to increase in several days. Mice in control and treated groups showed as the same profile in the changes of parasitemia. In the non-treated controls, after a transient peak parasitemia malaria parasites in the bloodstream of survivals could not be detected by a microscopic examination. During a mixture administration, all mice showed suppression of m

Topics: Administration, Oral; Animals; Antimalarials; Hydrangea; Malaria; Male; Mice; Mice, Inbred ICR; Parasitic Sensitivity Tests; Phytotherapy; Piperidines; Plant Extracts; Plant Leaves; Plasmodium; Plasmodium berghei; Plasmodium chabaudi; Plasmodium yoelii; Quinazolines

Quinazolinone type alkaloids, febrifugine (1) and isofebrifugine (2), isolated from Dichroa febrifuga roots, show powerful antimalarial activity against Plasmodium falciparum. Unfortunately, their emetic effect and other undesirable side effects have precluded their clinical use for malaria. Because of their antimalarial potency, analogues were searched for, with the goal of preserving the strong antimalarial activity, while dramatically reducing side effects. We expected that compounds useful in drug development would exist in metabolites derived from 1 and Df-1 (3), the condensation product of 1 with acetone, by mouse liver S9. Feb-A and -B (4 and 5) were isolated as the major metabolites of 1. In addition to 4 and 5, feb-C and -D (6 and 7) were also purified from the metabolic mixture of 3. Compounds 4 and 5 were compounds oxidized at C-6 and C-2 of the quinazolinone ring of 1, respectively. Compounds 6 and 7, derived from 3, also bear febrifugine type structures in which the 4' '- and 6' '-positions of the piperidine ring of 1 were oxidized. In vitro antimalarial and cytotoxic tests using synthetically obtained racemic 4-6 and enantiomerically pure 7 demonstrated that 4 and 6 had antimalarial activity against P. falciparum, of similar potency to that of 1, with high selectivity. The antimalarial activity of 5 and 7, however, was dramatically decreased in the test. The in vitro antimalarial activity of analogues 22 and 43, which are stereoisomers of 4 and 6, was also evaluated, showing that 22 is active. The results suggest that basicity of both the 1- and the 1' '-nitrogen atoms of 1 is crucial in conferring powerful antimalarial activity. Racemic 4 and 6 exhibited powerful in vivo antimalarial activity against mouse malaria P. berghei, and especially, no serious side effects were observed with 4. Thus, the metabolite 4 appears to be a promising lead compound for the development of new types of antimalarial drugs.

Topics: Administration, Oral; Animals; Antimalarials; Antineoplastic Agents; Dose-Response Relationship, Drug; Injections, Intraperitoneal; Liver; Mammary Neoplasms, Experimental; Mice; Nuclear Magnetic Resonance, Biomolecular; Piperidines; Plasmodium berghei; Plasmodium falciparum; Quinazolines; Stereoisomerism; Structure-Activity Relationship; Tumor Cells, Cultured

The combination effects of chloroquine with a mixture of febrifugine and isofebrifugine were evaluated against a blood-induced infection with chloroquine-resistant P. berghei NK65 in ICR mice. Mice in the untreated control showed a progressively increasing parasitemia leading to mouse death. A two-day dosage of 20 mg base/kg of chloroquine alone showed little effect against P. berghei NK65 infection, and all mice died from day 13 to 14 with an increasing parasitemia. A four-day dosage of 1 mg/kg of the febrifugine and isofebrifugine mixture alone showed a little antimalarial activity, but all mice died from day 19 to 27 with an increasing parasitemia. On the other hand, mice treated with chloroquine plus alkaloids survived during the experiment. All mice treated with chloroquine alone or the alkaloid mixture alone showed low parasitemia levels during a drug administration and following a few days, but then malaria parasites increased in the bloodstream of the treated mice until death. On the other hand, malaria parasites in the mice given chloroquine plus alkaloids decreased on day 6 and then were not detected by a microscopic examination during observation period.

Topics: Animals; Antimalarials; Chloroquine; Drug Administration Schedule; Drug Resistance; Drug Therapy, Combination; Malaria; Male; Mice; Mice, Inbred ICR; Parasitic Sensitivity Tests; Phytotherapy; Piperidines; Plasmodium berghei; Quinazolines

The stereo structure of piperidine lactone (3), an intermediate of the antimalarial agent febrifugine ((+)-1) prepared by a synthetic method, was re-revised to the cis-form from the trans-form.

Topics: Antimalarials; Indicators and Reagents; Lactones; Magnetic Resonance Spectroscopy; Models, Molecular; Molecular Conformation; Piperidines; Quinazolines

Although febrifugine (1) and isofebrifugine (2), alkaloids isolated from roots of the Dichroa febrifuga plant, show powerful antimalarial activity against Plasmodium falciparum, strong side effects such as the emetic effect have precluded their clinical use against malaria. However, their antimalarial potency makes them attractive substances as leads for developing new types of chemotherapeutic antimalarial drugs. Thus, we have evaluated the in vitro antimalarial activity of the analogues of febrifugine (1) and isofebrifugine (2). The activities of the analogues derived from Df-1 (3) and Df-2 (4), condensation products of 1 and 2 with acetone, respectively, were also obtained. The 3' '-keto derivative (7, EC(50) = 2.0 x 10(-8) M) of 1 was found to exhibit potential antimalarial activity with high selectivity against P. falciparum in vitro. The in vitro activities of the reduction product (8, EC(50) = 2.0 x 10(-8) M) of 1 at C-2' and its cyclic derivatives 9 and 10 (EC(50) = 3.7 x 10(-9) and 8.6 x 10(-9) M, respectively) were found to be strongly active and selective. Additionally, the Dess-Martin oxidation product of 3 was found to be strongly active with high selectivity against P. falciparum. A structure-activity relationship study (SAR) demonstrates that the essential role played by the 4-quinazolinone ring in the appearance of activity and the presence of a 1' '-amino group and C-2', C-3' ' O-functionalities are crucial in the activity of 1. For 7, 8, and 9, prepared as racemic forms, an in vivo study has also been conducted.

Topics: Animals; Antimalarials; Cell Line; Malaria; Mice; Piperidines; Plasmodium berghei; Plasmodium falciparum; Quinazolines; Structure-Activity Relationship

Reaction of (S)-2-(tert-butyldiphenylsilyloxy)-5-(mesyloxy)pentanal with hydroxylamine in allyl alcohol brought about simultaneous 1,3-dipolar cycloaddition of the resulting nitrone to allyl alcohol to give three diastereoisomeric adducts, from which (+)-febrifugine and (+)-isofebrifugine, potent antimalarial alkaloids, were synthesized.

Topics: Alkaloids; Antimalarials; Indicators and Reagents; Molecular Conformation; Molecular Structure; Piperidines; Quinazolines; Stereoisomerism

The regioisomers (2a,b) of the piperidine ring of febrifugine (1a) and isofebrifugine (1b) were synthesized from 4-allyl-3-piperidone (5). Reduction of 5 afforded a mixture of the trans and cis alcohols (6a,b) without diastereoselectivity; this result differentiated it from the reduction of 2-allyl-3-piperidone (14). The antimalarial activity of 2a,b and related compounds was tested.

Topics: Antimalarials; Piperidines; Quinazolines

Ring-opening reactions of semicyclic N,O-acetals possessing an exocyclic nitrogen atom with silicon-based nucleophiles (silyl enol ethers, ketene silyl acetals, allylic silanes, and trimethylsilyl cyanide) were systematically studied for the first time. It was found that the reactions were effectively catalyzed by a Lewis acid, trimethylsilyl trifluoromethanesulfonate (TMSOTf), to afford 1,4- and 1,5-amino alcohols in high yields. In reactions of 3-oxygen functionalized semicyclic N,O-acetals, high 1,2-syn-diastereoselectivity was obtained. By 1H NMR experiment, the formation of the O-trimethylsilylated ring-opened product was observed as the initial product. Furthermore, the epimerization between the diastereomers of a 3-benzyloxy semicyclic N,O-acetal suggested the transient formation of an acyclic iminium ion species as a reactive intermediate. It was also found that 3-acetoxy and 3-benzyloxy N,O-acetals showed a tendency for the larger nucleophile to provide higher syn-selectivity, while 3-tert-butyldiphenylsilyloxy N,O-acetals showed the opposite tendency. These stereochemical outcomes can be rationalized by assuming four transition state models for the acyclic iminium ion intermediate. The synthetic utility of the reaction has been demonstrated in the diastereoselective synthesis of piperidine alkaloids, (+)-isofebrifugine and (+/-)-sedacryptine.

Topics: Acetals; Acids; Alkaloids; Ethers, Cyclic; Nitrogen; Piperidines; Quinazolines; Stereoisomerism

A diastereocontrolled synthesis of (+)-febrifugine, a potent antimalarial piperidine alkaloid, has been achieved using a chiral block having a bicyclo[3.2.1]octane framework which exhibits inherent convex-face selectivity.

Topics: Alkaloids; Antimalarials; Piperidines; Plants, Medicinal; Quinazolines; Stereoisomerism

Febrifugine (1) and isofebrifugine (2), isolated from the roots of Dichroa febrifuga Lour. (Chinese name: Cháng Shan), are active principles against malaria. Adducts of 1 and 2 with acetone, Df-1 (3) and Df-2 (4), respectively, were obtained using silica gel and acetone. They showed high activity against P. falciparum malaria in vitro. Compound 3 was found to be equally effective against P. berghei in vivo as the clinically used drug chloroquine, whereas 4 showed only 1/24 of the activity of 3. Metabolism studies of these compounds revealed that compound 4 is readily metabolized in mouse liver. Accordingly, the dose of 4 must be higher than that of 3 to attain blood levels sufficient for a favorable therapeutic effect.

Topics: Animals; Antimalarials; Drugs, Chinese Herbal; Malaria; Male; Mice; Mice, Inbred ICR; Models, Molecular; Molecular Conformation; Piperidines; Plasmodium berghei; Plasmodium falciparum; Quinazolines; Quinazolinones; Quinolizines

The effect of febrifugine, the main alkaloidal constituent of an antimalarial crude drug, Dichroa febrifuga Lour., on protective immunity in mice infected with erythrocytic stage Plasmodium berghei NK65 was investigated. Febrifugine was administered orally, at a dose of 1 mg/kg/day, to mice before and/or after they were infected intraperitoneally with 2 x 10(6) parasitized red blood cells. Then, mortality and the levels of parasitemia and plasma NO3- [a degradation product of nitric oxide (NO)] were monitored. Febrifugine significantly reduced the mortality and the level of parasitemia. The plasma NO3- concentration began to rise within 2 days after treatment with febrifugine and declined to normal in 2 days when the mice were treated orally with febrifugine once a day for 3 consecutive days before parasite infection. This antimalarial activity of febrifugine was reduced by both N(G)-monomethyl-L-arginine and aminoguanidine. These results indicate that the increased production of NO by febrifugine plays an important role in host defense against malaria infection in mice.

Topics: Animals; Antimalarials; Drug Interactions; Enzyme Inhibitors; Malaria; Male; Mice; Mice, Inbred ICR; Nitrates; Nitric Oxide; Nitric Oxide Synthase; Parasitemia; Piperidines; Plasmodium berghei; Quinazolines

The effect of an antimalarial crude drug, Dichroafebrifuga Lour. on nitric oxide (NO) production in bacillus Calmette Guérin-induced mouse peritoneal macrophages activated by lipopolysaccharide was investigated. The NO production was significantly enhanced by an oral administration of a MeOH extract of D. febrifuga. Febrifugine (1) was isolated as the main active compound, and the activation was dose-dependent in the dosage range of 0.1-1 mg/kg/day.

Topics: Animals; Antimalarials; China; In Vitro Techniques; Macrophages; Male; Mass Spectrometry; Mice; Mice, Inbred ICR; Nitric Oxide; Piperidines; Plant Extracts; Plant Roots; Plants, Medicinal; Quinazolines; Spectrophotometry, Infrared; Spectrophotometry, Ultraviolet

Topics: Antimalarials; Chloroquine; Models, Structural; Piperidines; Quinazolines; Structure-Activity Relationship

Topics: Animals; Antimalarials; Female; Male; Mice; Piperidines; Plasmodium; Quinazolines

Topics: Alkaloids; Animals; Antineoplastic Agents; Piperidines; Quinazolines

Topics: Alkaloids; Malaria; Piperidines; Plants; Plasmodium vivax; Quinazolines