deoxyartemisinin and artemisinin

The biotransformation of the front-line antimalarial drug, artemisinin (1) by the filamentous fungus Aspergillus flavus MTCC-9167 was investigated. Incubation of compound 1 with A. flavus afforded a new hydroxy derivative (2) along with three known metabolites (3-5). The new compound was characterized as 14-hydroxydeoxyartemisinin (2) by extensive spectroscopic data analysis (IR,

Topics: Antimalarials; Artemisinins; Aspergillus flavus; Biotransformation; Hydroxylation; Magnetic Resonance Spectroscopy; Molecular Structure

Dihydroartemisinin (DHA, 1), a sesquiterpene endoperoxide derived from artemisinin, has shown potent antimalarial and anticancer activities. Microbial transformation of DHA by Absidia coerulea and Penicillium chrysogenum yielded one new (3) and four known metabolites (2, 4-6). The chemical structures of these compounds were identified as deoxydihydroartemisinin (2), 8α-hydroxydeoxyartemisinin (3), deoxyartemisinin (4), 9α-hydroxyartemethin-I (5) and 3α-hydroxydeoxydihydroartemisinin (6) using spectroscopic analyses. Among them, compounds 3 and 4 are artemisinin analogues, which were achieved by unusual oxidation at C-12 position. Biotransformation of DHA by microorganisms was an effective approach to obtain new derivatives of DHA.

Topics: Absidia; Antimalarials; Artemisinins; Biotransformation; Molecular Structure; Oxidation-Reduction; Penicillium chrysogenum

The Chinese have used Artemisia annua as a tea infusion to treat fever for >2000 years. The active component is artemisinin. Previously we showed that when compared to mice fed an equal amount of pure artemisinin, a single oral dose of dried leaves of Artemisia annua (pACT) delivered to Plasmodium chabaudi-infected mice reduced parasitemia at least fivefold. Dried leaves also delivered >40 times more artemisinin in the blood with no toxicity. The pharmacokinetics (PK) of artemisinin delivered from dried plant material has not been adequately studied.. Healthy and Plasmodium chabaudi-infected mice were oral gavaged with pACT to deliver a 100 mg kg(-1) body weight dose of artemisinin. Concentrations of serum artemisinin and one of its liver metabolites, deoxyartemisinin, were measured over two hours by GCMS.. The first order elimination rate constant for artemisinin in pACT-treated healthy mice was estimated to be 0.80 h(-1) with an elimination half-life (T½) of 51.6 min. The first order absorption rate constant was estimated at 1.39 h(-1). Cmax and Tmax were 4.33 mg L(-1) and 60 min, respectively. The area under the curve (AUC) was 299.5 mg min L(-1). In contrast, the AUC for pACT-treated infected mice was significantly greater at 435.6 mg min L(-1). Metabolism of artemisinin to deoxyartemisinin was suppressed in infected mice over the period of observation. Serum levels of artemisinin in the infected mice continued to rise over the 120 min of the study period, and as a result, the T½ was not determined; the Cmax and Tmax were estimated at ≥6.64 mgL(-1) and ≥120 min, respectively. Groups of healthy mice were also fed either artemisinin or artemisinin mixed in mouse chow. When compared at 60 min, artemisinin was undetectable in the serum of mice fed 100 mg AN kg(-1) body weight. When plant material was present either as mouse chow or Artemisia annua pACT, artemisinin levels in the serum rose to 2.44 and 4.32 mg L(-1), respectively, indicating that the presence of the plant matrix, even that of mouse chow, had a positive impact on the appearance of artemisinin in the blood.. These results showed that artemisinin and one of its drug metabolites were processed differently in healthy and infected mice. The results have implications for possible therapeutic use of pACT in treating malaria and other artemisinin-susceptible diseases.

Topics: Administration, Oral; Animals; Antimalarials; Artemisia annua; Artemisinins; Malaria; Male; Mice, Inbred C57BL; Plant Leaves; Plasmodium chabaudi

Biotransformation of antimalarial drug artemisinin by fungi Rhizopus stolonifer afforded three sesquiterpenoid derivatives. The transformed products were 1α-hydroxyartemisinin (3), 3.0%, a new compound, 10β-hydroxyartemisinin, 54.5% (4) and deoxyartemisinin (2) in 9% yield. The fungus expressed high-metabolism activity (66.5%). The chemical structures of the compounds were elucidated by 1D, 2D NMR spectrometry and mass spectral data. The major compound 10β-hydroxyartemisinin (4) was chemically converted to five new derivatives 5-9. All the compounds 3-9 were subjected for in vitro anti-malarial activity. 10β-Hydroxy-12β-arteether (8), IC50 at 18.29nM was found to be 10 times better active than its precursor 4 (184.56nM) and equipotent antimalarial with natural drug artemisinin whereas the α-derivative 9 is 3 times better than 4 under in vitro conditions. Therefore, the major biotransformation product 4 can be exploited for further modification into new clinically potent molecules. The results show the versatility of microbial-catalyzed biotransformations leading to the introduction of a hydroxyl group at tertiary position in artemisinin in derivative (3).

Topics: Antimalarials; Artemisinins; Biotransformation; England; Humans; India; Molecular Structure; Parasitic Sensitivity Tests; Plasmodium falciparum; Rhizopus; Sesquiterpenes

Medicinal plants are a rich source of biologically-active phytochemicals and have been used in traditional medicine for centuries. Specific phytochemicals and extracts of their plant sources have the ability to reduce the risk for chronic degenerative diseases by induction of enzymes involved in xenobiotic metabolism, many of which also have antioxidant and anti-inflammatory functions. One such multifunctional cytoprotective enzyme is NAD(P)H : quinone oxidoreductase. In this study, we prepared extracts of 27 Saudi Arabian medicinal plants which belong to 18 different plant families and tested their ability to induce NAD(P)H : quinone oxidoreductase in murine hepatoma cells grown in microtiter plate wells. In addition to the Brassicaceae, a known source of NAD(P)H : quinone oxidoreductase inducer activity, we found substantial inducer activity in extracts from the Apiaceae, Apocynaceae, and the Asteraceae families. Five out of a total of eight active extracts are from plants which belong to the Asteraceae family. We further show that artemisinin, an agent which is used clinically for the treatment of malaria, contributes but does not fully account for the inducer activity of the extract of Artemisia monosperma. In contrast to artemisinin, deoxyartemisinin is inactive in this assay, demonstrating the critical role of the endoperoxide moiety of artemisinin for inducer activity. Thus, the NAD(P)H : quinone oxidoreductase inducer activity of extracts of some Saudi Arabian medicinal plants indicates the presence of specific phytochemicals which have the potential to protect against chronic degenerative diseases.

Topics: Animals; Artemisinins; Asteraceae; Mice; NAD(P)H Dehydrogenase (Quinone); Plant Extracts; Plants, Medicinal; Saudi Arabia; Tumor Cells, Cultured

Artemisinin derivatives such as dihydroartemisinin (DHA) induce significant depletion of early embryonic erythroblasts in animal models. We have reported previously that DHA specifically targets pro-erythroblasts and basophilic erythroblasts, when human CD34+ stem cells are differentiated toward the erythroid lineage, indicating that a window of susceptibility to artemisinins may exist also in human developmental erythropoiesis during pregnancy. To better investigate the toxicity of artemisinin derivatives, the structure-activity relationship was evaluated against the K562 leukaemia cell line, used as a model for differentiating early human erythroblasts. All artemisinins derivatives, except deoxyartemisinin, inhibited both spontaneous and induced erythroid differentiation, confirming that the peroxide bridge is responsible for the erythro-toxicity. On the contrary, cell growth was markedly reduced by DHA, artemisone and artesunate but not by artemisinin, 10-deoxoartemisinin or deoxy-artemisinin. The substituent at position C-10 is responsible only for the anti-proliferative effect, since 10-deoxoartemisinin did not reduce cell growth but arrested the differentiation of K562 cells. In particular, the results showed that DHA resulted the most potent and rapidly acting compound of the drug family, causing (i) the decreased expression of GpA surface receptors and the down regulation the γ-globin gene; (ii) the alteration of S phase of cell cycle and (iii) the induction of programmed cell death of early erythroblasts in a dose dependent manner within 24h. In conclusion, these findings confirm that the active metabolite DHA is responsible for the erythro-toxicity of most of artemisinins used in therapy. Thus, as long as no further clinical data are available, current WHO recommendations of avoiding malaria treatment with artemisinins during the first trimester of pregnancy remain valid.

Topics: Artemisinins; Cell Cycle; Cell Differentiation; Erythroid Cells; Flow Cytometry; Humans; K562 Cells; Reverse Transcriptase Polymerase Chain Reaction; Structure-Activity Relationship

By using 6,7,8-trioxabicyclo[3.2.2]nonane as the artemisinin model and dihydrated Fe(OH)(2) as the heme model, we report a theoretical study of the late steps of the artemisinin decomposition process. The study offers two viewpoints: first, the energetic and geometric parameters are obtained and analyzed, and hence, different reaction paths have been studied. The second point of view uses the electron localization function (ELF) and the atoms in molecules (AIM) methodology, to conduct a complete topological study of such steps. The MO analysis together with the spin density description has also been used. The obtained results agree nicely with the experimental data, and a new mechanistic proposal that explains the experimentally determined outcome of deoxiartemisinin has been postulated.

Topics: Alkanes; Artemisinins; Bridged Bicyclo Compounds, Heterocyclic; Computer Simulation; Electrons; Ferrous Compounds; Heme; Hemeproteins; Hemoglobins; Models, Chemical; Models, Molecular; Models, Theoretical; Molecular Mimicry; Oxidation-Reduction; Plasmodium; Reactive Oxygen Species; Thermodynamics

The biological mode of action of artemisinin, a potent antimalarial, has long been controversial. Previously we established a yeast model addressing its mechanism of action and found mitochondria the key in executing artemisinin's action. Here we present data showing that artemisinin directly acts on mitochondria and it inhibits malaria in a similar way as yeast. Specifically, artemisinin and its homologues exhibit correlated activities against malaria and yeast, with the peroxide bridge playing a key role for their inhibitory action in both organisms. In addition, we showed that artemisinins are distributed to malarial mitochondria and directly impair their functions when isolated mitochondria were tested. In efforts to explore how the action specificity of artemisinin is achieved, we found strikingly rapid and dramatic reactive oxygen species (ROS) production is induced with artemisinin in isolated yeast and malarial but not mammalian mitochondria, and ROS scavengers can ameliorate the effects of artemisinin. Deoxyartemisinin, which lacks an endoperoxide bridge, has no effect on membrane potential or ROS production in malarial mitochondria. OZ209, a distantly related antimalarial endoperoxide, also causes ROS production and depolarization in isolated malarial mitochondria. Finally, interference of mitochondrial electron transport chain (ETC) can alter the sensitivity of the parasite towards artemisinin. Addition of iron chelator desferrioxamine drastically reduces ETC activity as well as mitigates artemisinin-induced ROS production. Taken together, our results indicate that mitochondrion is an important direct target, if not the sole one, in the antimalarial action of artemisinins. We suggest that fundamental differences among mitochondria from different species delineate the action specificity of this class of drugs, and differing from many other drugs, the action specificity of artemisinins originates from their activation mechanism.

Topics: Anti-Infective Agents; Antimalarials; Artemisinins; Malaria; Mitochondria; Mitochondrial Membranes; Models, Chemical; Oxygen Consumption; Peroxides; Plasmodium berghei; Plasmodium falciparum; Reactive Oxygen Species

Artemisinin, an antimalarial compound, at 5 mg/40 ml, was transformed by cell suspension cultures of Catharanthus roseus (L.) G.Don and Lavandula officinalis L. into deoxyartemisinin with yields >78% (3.93 mg deoxyartemisinin from 5 mg artemisinin). Maximum conversion (78.6 and 78%) occurred after 6 and 7 days of adding artemisinin to 20 and 9 days old cultures of C. roseus and L. officinalis, respectively. The procedure was scaled up by and 500 mg artemisinin was transformed into 390 mg deoxyartemisinin. Addition of artemisinin at the beginning of the culture cycle resulted in >50% reduction in dry biomass production with no bioconversion. Conversion of artemisinin occurred intracellularly followed by leaching of the product into the medium.

Topics: Artemisinins; Biotransformation; Catharanthus; Cell Culture Techniques; Lavandula

Artemisinin is a plant sesquiterpene lactone that has become an important drug for combating malaria, especially in regions where resistance to other drugs is widespread. While the mechanism of action is debated, artemisinin has been reported to inhibit the sarcoplasmic endoplasmic reticulum Ca(2+) ATPase (SERCA) in the malaria parasite. Artemisinin is also effective against Toxoplasma in vitro and in vivo, although it is less potent and, hence, is generally not used therapeutically to treat toxoplasmosis. To explore the mechanism of action, we generated chemically derived mutants of Toxoplasma gondii that were resistant to growth inhibition by this compound in vitro. Three artemisinin-resistant (ART(r)) mutant clones that differed in their sensitivities in vitro by three- to fivefold compared with that of the wild-type parasites were obtained. ART(r) mutants were cross-resistant to other derivatives of artemisinin, the most potent of which was artemisone. Resistance was not due to molecular alterations or differences in the expression of SERCA or other putative targets, such as proteins that code for multidrug resistance or translationally controlled tumor protein. ART(r) mutants were resistant to the induction of protein secretion from micronemes, a calcium-dependent process that is triggered by artemisinin. ART(r) mutants were not cross-resistant to secretion induced by thapsigargin but were more sensitive and were unable to regulate cytoslic calcium following treatment with this compound. These studies implicate calcium homeostasis in the mechanism of action of artemisinins against apicomplexan parasites.

Topics: Animals; Antiprotozoal Agents; Artemisinins; Blotting, Western; Calcium; Calcium-Transporting ATPases; Drug Resistance; Homeostasis; Mutagenesis; Mutation; Sarcoplasmic Reticulum; Toxoplasma

Artemisinin (1) and its analogues have been well studied for their antimalarial activity. Here we present the antimalarial activity of some novel C-9-modified artemisinin analogues synthesized using artemisitene as the key intermediate. Further, antileishmanial activity of more than 70 artemisinin derivatives against Leishmania donovani promastigotes is described for the first time. A comprehensive structure-activity relationship study using CoMFA is discussed. These analogues exhibited leishmanicidal activity in micromolar concentrations, and the overall activity profile appears to be similar to that against malaria. Substitution at the C-9beta position was shown to improve the activity in both cases. The 10-deoxo derivatives showed better activity compared to the corresponding lactones. In general, compounds with C-9alpha substitution exhibited lower antimalarial as well as antileishmanial activities compared to the corresponding C-9beta analogues. The importance of the peroxide group for the observed activity of these analogues against leishmania was evident from the fact that 1-deoxyartemisinin analogues did not exhibit antileishmanial activity. The study suggests the possibility of developing artemisinin analogues as potential drug candidates against both malaria and leishmaniasis.

Topics: Animals; Antimalarials; Antiprotozoal Agents; Artemisinins; Clone Cells; Drug Design; Inhibitory Concentration 50; L-Lactate Dehydrogenase; Leishmania donovani; Malaria, Falciparum; Models, Molecular; Molecular Conformation; Plasmodium falciparum; Sesquiterpenes; Static Electricity; Stereoisomerism; Structure-Activity Relationship

Artemisinin (1) is a unique sesquiterpene peroxide occurring as a constituent of Artemisia annua L. Because of the effectiveness of Artemisinin in the treatment of drug-resistant Plasmodium falciparum and its rapid clearance of cerebral malaria, development of clinically useful semisynthetic drugs for severe and complicated malaria (artemether, artesunate) was prompt. However, recent reports of fatal neurotoxicity in animals with dihydroartemisinin derivatives such as artemether have spawned a renewed effort to develop nontoxic analogues of artemisinin. In our effort to develop more potent, less neurotoxic agents for the oral treatment of drug-resistant malaria, we utilized comparative molecular field analysis (CoMFA) and hologram QSAR (HQSAR), beginning with a series of 211 artemisinin analogues with known in vitro antimalarial activity. CoMFA models were based on two conformational hypotheses: (a) that the X-ray structure of artemisinin represents the bioactive shape of the molecule or (b) that the hemin-docked conformation is the bioactive form of the drug. In addition, we examined the effect of inclusion or exclusion of racemates in the partial least squares (pls) analysis. Databases derived from the original 211 were split into chiral (n = 157), achiral (n = 34), and mixed databases (n = 191) after leaving out a test set of 20 compounds. HQSAR and CoMFA models were compared in terms of their potential to generate robust QSAR models. The r(2) and q(2) (cross-validated r(2)) were used to assess the statistical quality of our models. Another statistical parameter, the ratio of the standard error to the activity range (s/AR), was also generated. CoMFA and HQSAR models were developed having statistically excellent properties, which also possessed good predictive ability for test set compounds. The best model was obtained when racemates were excluded from QSAR analysis. Thus, CoMFA of the n = 157 database gave excellent predictions with outstanding statistical properties. HQSAR did an outstanding job in statistical analysis and also handled predictions well.

Topics: Antimalarials; Artemisinins; Databases, Factual; Models, Molecular; Molecular Conformation; Quantitative Structure-Activity Relationship; Reproducibility of Results; Sesquiterpenes; Stereoisomerism

Photooxygenation of anhydrodeoxydihydroartemisinin (4) followed by chromatographic separation of the reaction mixture yielded the new compounds alpha- (5) and beta-hydroperoxydeoxyartemisitene (8) and the formate ester 7, together with two previously reported compounds, 6 and 9. Reduction of 5 using polymer-bound triphenylphosphine afforded the new compound dihydrodeoxyartemisitene (10). Treatment of 10 with a catalytic amount of BF(3)-OEt(2) yielded the C(2)-symmetrical dimer bis(dihydrodeoxyartemisitene) ether (11) and two new compounds, dihydrodeoxyartemisitene methyl ether (12) and the dimer 13, as minor products. Dehydroacetoxylation of 5 using acetic anhydride in pyridine afforded deoxyartemisitene (14). The identities of the new compounds (5, 7, 8, 10-14) were deduced from their spectral data and by chemical derivatization. The stereochemistry of dimer 11 was defined on the basis of X-ray crystallographic analysis. All compounds were evaluated in vitro in the National Cancer Institute drug-screening program consisting of 60 human cancer cell lines derived from nine different tissues. Of the compounds tested, deoxyartemisitene (14) demonstrated significant cytotoxicity against a number of human cancer cell lines.

Topics: Antineoplastic Agents, Phytogenic; Artemisia; Artemisinins; Breast Neoplasms; Carcinoma, Non-Small-Cell Lung; Crystallography, X-Ray; Drug Screening Assays, Antitumor; Female; Humans; Lung Neoplasms; Magnetic Resonance Spectroscopy; Molecular Conformation; Molecular Structure; Oxidation-Reduction; Oxygen; Photochemistry; Saudi Arabia; Sesquiterpenes; Stereoisomerism; Structure-Activity Relationship; Tumor Cells, Cultured

Artemisinin 1, dihydro-epideoxyarteannuin B 2 and deoxyartemisinin 3 were isolated from the sequiterpene lactone-enriched fraction obtained from the crude ethanolic extract of Artemisia annua L. These compounds were tested on ethanol and indomethacin-induced ulcer models. Compound 1 did not afford cytoprotection under the experimental models tested. Only compounds 2 and 3 decreased the ulcerative lesion index produced by ethanol and indomethacin in rats. These compounds did not demonstrate antiulcerogenic activity when tested on the ethanol-induced ulcer model, with previous administration of indomethacin, suggesting that the antiulcerogenic activity is a consequence of prostaglandin synthesis increase.

Topics: Animals; Anti-Ulcer Agents; Artemisinins; Asteraceae; Carbenoxolone; Cimetidine; Drug Interactions; Ethanol; Indomethacin; Male; Phytotherapy; Plant Extracts; Rats; Rats, Wistar; Sesquiterpenes; Stomach; Stomach Ulcer

We determined the cytotoxicity of some artemisinin derivatives against EN2 tumor cells using the MTT assay. Artemisinin (1) was clearly more cytotoxic than deoxyartemisinin (2), which lacks the endoperoxide bridge. Ether-linked dimers of dihydroartemisinin with defined stereochemistry were found to differ in the extent of cytotoxic effect on EN2 cells. The nonsymmetrical dimer (3) was more cytotoxic than the symmetrical dimer (4). The nonsymmetrical dimer of dihydrodeoxyartemisinin (5) lacking the endoperoxide bridges was also effective in the MTT assay, although less cytotoxic than 3 and 4. Similarly, the symmetrical dimer (6) was less effective than 5. Epoxides of artemisitene also showed that stereochemistry was an important factor for cytotoxicity. The results suggested that the endoperoxide bridge was not crucial for cytotoxicity to the tumor cells, but contributed to the cytotoxic effect apparently exerted by the ether linkage of the dimers. Flow cytometry data indicated that the dimers 3 and 4 caused an accumulation of the cells in the G1-phase of the cell cycle. In contrast, artemisinin (1) caused a slight increase of S-phase cells.

Topics: Antineoplastic Agents, Phytogenic; Artemisinins; Cell Cycle; Drug Screening Assays, Antitumor; Flow Cytometry; Humans; Sesquiterpenes; Stereoisomerism; Structure-Activity Relationship; Tetrazolium Salts; Thiazoles; Tumor Cells, Cultured

Artemisinin (qinghaosu, QHS) is a promising new antimalarial agent that is effective against drug-resistant strains of malaria. The antimalarial activity of this drug appears to be mediated by an interaction of the drug's endoperoxide bridge with intraparasitic hemin. We have carried out a computer-assisted docking of QHS with hemin from various starting configurations and found that, in the most stable docked configuration, the endoperoxide bridge is in close proximity to the hemin iron. In contrast, an inactive analog, deoxyartemisinin (DQHS), docks in a different manner. Further computer analysis of the drug-hemin interaction might aid in the design of new QHS congeners.

Topics: Antimalarials; Artemisinins; Computer Simulation; Drug Design; Drugs, Chinese Herbal; Hemin; Iron; Models, Molecular; Receptors, Cytoplasmic and Nuclear; Sesquiterpenes

A novel class of artemisinin analogs, N-alkyl-11-aza-9-desmethylartemisinins 17-29, were synthesized via ozonolysis and acid-catalyzed cyclization of precursor amides 5-16. These amides were prepared through condensation of an activated ester of the known intermediate acid 2 with the corresponding primary amine. The analogs were tested in vitro against W-2 and D-6 strains of Plasmodium falciparum and found in some cases to be more active than artemisinin. A comparison of the in vitro testing methods of Milhous and Makler was conducted and gave similar relative antimalarial activities for these artemisinin analogs. Log P values were determined for most of the compounds, but no apparent correlation between log P and in vitro activity was found.

Topics: Animals; Antimalarials; Artemisinins; Drug Evaluation, Preclinical; Drugs, Chinese Herbal; Erythrocytes; Humans; Molecular Structure; Plasmodium falciparum; Sesquiterpenes; Structure-Activity Relationship

A series of C-9 beta-substituted artemisinin analogs (2-21) were synthesized via dianion alkylation of the total synthetic intermediate 57 followed by subsequent ozonolysis/acidification, or by alkylation of the enolate derived from (+)-9-desmethylartemisinin, 2. Inactive acyclic analogs 22 and 23 were synthesized by nucleophilic epoxide opening and the ring contracted analog 24 was prepared by an alternate route. 10-Deoxo-9-alkyl derivatives 68 and 70 were synthesized convergently from intermediates in the preparation of 9-alkyl derivatives. In vitro bioassay was conducted in W-2 and D-6 clones of drug resistant Plasmodium falciparum. Comparative molecular field analysis (CoMFA) of the 9-alkyl lactone derivatives provided a model with a cross-validated r2 = 0.793. Inclusion of inactive 1-deoxyartemisinin analogs 26-42 provided a model with a value of 0.857. The activities of a number of other analogs of divergent structure (43-56) were predicted with good accuracy using the CoMFA model.

Topics: Animals; Antimalarials; Artemisinins; Chemical Phenomena; Chemistry, Physical; Computer Simulation; Drug Resistance; Electrochemistry; Models, Molecular; Molecular Conformation; Molecular Structure; Plasmodium falciparum; Sesquiterpenes; Structure-Activity Relationship

Topics: Animals; Antimalarials; Artemisinins; Chromatography, Thin Layer; Mice; Sesquiterpenes; Spectrometry, Fluorescence