Nicolas Taudon

Stability and antiviral activity against human cytomegalovirus of artemisinin derivatives

OBJECTIVES Artesunate, a derivative of dihydroartemisinin, itself a product of artemisinin, inhibits the replication of cytomegalovirus in vitro. In vivo, artesunate undergoes rapid conversion into the active metabolite dihydroartemisinin. The in vitro stability of the compounds and the antiviral activity of dihydroartemisinin are of great concern for the interpretation of in vitro testing. The aim of the study was to measure artesunate conversion into dihydroartemisinin in culture medium and to evaluate the stability and antiviral activity of artemisinin derivatives, according to culture conditions. METHODS Conversion of artesunate into dihydroartemisinin was measured in culture medium with or without fetal calf serum, in the presence or absence of fibroblast monolayers, at different times. The stability of artemisinin derivatives was determined in serum-enriched medium. Concentrations of each compound inhibiting viral DNA synthesis by 50% were determined in fibroblasts cultured in serum-free or serum-enriched medium, after addition of compound as a single dose or fractional doses. RESULTS Conversion of artesunate into dihydroartemisinin in serum-free or serum-enriched medium was non-equimolar. The half-lives of artesunate, dihydroartemisinin and artemisinin were 10.3 ± 0.9, 5.2 ± 0.5 and 11.2 ± 1.2 h, respectively. Activity of dihydroartemisinin and artesunate was markedly reduced in serum-starved cells. Unexpectedly, dihydroartemisinin displayed a lower activity than artesunate. Addition of both compounds as fractional doses increased their activity. Artemisinin had no anticytomegaloviral activity. CONCLUSIONS Artemisinin derivatives were shown to be unstable in vitro and their addition as fractional doses could partly compensate for this instability. Importantly, the cellular physiological condition was a determinant of their antiviral activity.

Differences in anti-malarial activity of 4-aminoalcohol quinoline enantiomers and investigation of the presumed underlying mechanism of action

BackgroundA better anti-malarial efficiency and lower neurotoxicity have been reported for mefloquine (MQ) (+)- enantiomer. However, the importance of stereoselectivity remains poorly understood as the anti-malarial activity of pure enantiomer MQ analogues has never been described. Building on these observations, a series of enantiopure 4-aminoalcohol quinoline derivatives has previously been synthesized to optimize the efficiency and reduce possible adverse effects. Their in vitro activity on Plasmodium falciparum W2 and 3D7 strains is reported here along with their inhibition of β-haematin formation and peroxidative degradation of haemin, two possible mechanisms of action of anti-malarial drugs.ResultsThe (S)-enantiomers of this series of 4-aminoalcohol quinoline derivatives were found to be at least as effective as both chloroquine (CQ) and MQ. The derivative with a 5-carbon side-chain length was the more efficient on both P. falciparum strains. (R )-enantiomers displayed an activity decreased by 2 to 15-fold as compared to their (S) counterparts. The inhibition of β-haematin formation was significantly stronger with all tested compounds than with MQ, irrespective of the stereochemistry. Similarly, the inhibition of haemin peroxidation was significantly higher for both (S) and (R)-enantiomers of derivatives with a side-chain length of five or six carbons than for MQ and CQ.ConclusionsThe prominence of stereochemistry in the anti-malarial activity of 4-aminoalcohol quinoline derivatives is confirmed. The inhibition of β-haematin formation and haemin peroxidation can be put forward as presumed mechanisms of action but do not account for the stereoselectivity of action witnessed in vitro.

Malaria Prophylaxis Failure with Doxycycline, Central African Republic, 2014

To the Editor: Doxycycline is an effective antimalarial prophylactic drug when administered as a monotherapy 1 day before, daily during, and for 4 weeks after travel to an area where malaria is endemic (1). Doxycycline is currently a recommended chemoprophylactic regimen for travelers visiting areas where malaria is endemic and has a high prevalence of chloroquine or multidrug resistance (2). The World Health Organization also recommends doxycycline in combination with quinine or artesunate as the second-line treatment for uncomplicated Plasmodium falciparum malaria (3). Prophylactic and clinical failures of doxycycline against P. falciparum have been associated with both inadequate doses (4) and poor patient compliance (5). However, resistance can also explain failures of prophylaxis. Cycline resistance in Plasmodium spp. has been documented as a consequence of selective drug pressure in a P. berghei murine malaria model (6). The administration of increasing doses of minocycline to mice infected with 1 × 107 parasites for 86 successive passages over 600 days made it possible to obtain a resistant P. berghei strain with a median drug inhibitory concentration (IC50) of 600 mg/kg/d, which is 6-fold higher than that of the susceptible starting strain (100 mg/kg/d) (6). A Bayesian mixture modeling approach identified 3 different phenotypes (low, medium, and high doxycycline IC50 phenotypic groups) among P. falciparum clinical isolates (7,8). Using 90 isolates from 14 countries, we demonstrated that increases in copy numbers of P. falciparum metabolite drug transporter gene (Pfmdt, PFE0825w) and P. falciparum GTPase TetQ gene (PfTetQ, PFL1710c) are associated with reduced susceptibility to doxycycline (9); this association was later confirmed (7). In addition, isolates with PfTetQ KYNNNN motif repeats are associated with in vitro reduced susceptibility to doxycycline and with a significantly higher probability of having an IC50 above the doxycycline resistance threshold of 35 μM (9,10). We report a case of documented malaria prophylactic failure with doxycycline in a 26-year-old soldier from France who was infected during a 6-week peacekeeping mission in the Central African Republic in 2014. According to his colleagues and the collective prophylaxis intake, the patient had been compliant with doxycycline prophylaxis. On admission to a hospital in Bangui, Central African Republic, the patient had fever (temperature 40°C), alteration of consciousness, and hypotension. The diagnosis of severe P. falciparum malaria was made on the basis of a rapid diagnostic test confirmed by a blood smear test (parasitemia 8% on day 0). Intravenous artesunate was immediately started, in accordance with World Health Organization recommendations (3). The patient’s clinical condition worsened, and kidney failure developed. Twenty-four hours later (day 1), he was transported by airplane to Begin Military Teaching Hospital (Saint-Mande, France). On admission, he had cerebral edema and a P. falciparum parasitemia level of 0.7%. The patient died 1 day later (day 2). A blood sample obtained from the patient on day 1 in France showed a doxycycline concentration of 195 μg/mL plasma. This concentration, which was determined by liquid chromatography coupled with tandem mass spectrometry, was compatible with a last doxycycline uptake 1 day before diagnosis (day −1). The finding of the expected doxycycline plasma concentration, together with assurances (colleague’s statements and collective intake of doxycycline) that the patient had followed the drug regimen, was sufficient to suggest prophylaxis failure in a treatment-compliant patient. The P. falciparum sample obtained from the patient on arrival in France was evaluated for in vitro susceptibility to doxycycline, but the evaluation was unsuccessful. The number of copies of PfTetQ and Pfmdt genes were evaluated relative to the single-copy P. falciparum β-tubulin gene (pfβtubulin), as previously described (7,8). The sample was assayed in triplicate. The 2–ΔΔCt method (where Ct indicates cycle threshold) of relative quantification was used and adapted to estimate the number of copies of Pfmdt and PfTetQ by using the formula ΔΔCt = (Ct (PfTetQ or Pfmdt) − Ct (Pfβtubulin))Sample – (Ct (PfTetQ or Pfmdt) − Ct (Pfβtubulin))Calibrator. Genomic DNA extracted from 3D7 P. falciparum, which has a single copy of each gene, was used for calibrator sample; Pfβtubulin served as the control housekeeping gene. The experiment was assayed twice. The sample had 2 copies of PfTetQ and Pfmdt genes, which suggested decreased in vitro susceptibility of the sample to doxycycline (8,9). The genotyping of PfTetQ sequence polymorphisms was done by using conventional methods with the primers PfTetQ forward (5′-TCACGACAAATGTGCTAGATAC-3′) and PfTetQ reverse (5′-ATCATCATTTGTGGTGGATAT-3′), as previously described (10). Two PfTetQ KYNNNN motif repeats were found in the sample; 35 μM (odds ratio 15) (10). The 2 copies of Pfmdt and the 2 KYNNNN motif repeats have been shown to be associated with parasites with in vitro resistance to doxycycline (9,10). The association of doxycycline resistance (prophylactic failure with statement of correct intake and the presence of an expected concentration) with increased Pfmdt copies and decreased PfTetQ KYNNNN motif repeats suggest that these molecular markers are predictive markers of doxycycline resistance that can be used for resistance surveillance.

In vitro and in vivo combination of cepharanthine with anti-malarial drugs

BackgroundStephania rotunda is used by traditional health practitioners in Southeast Asia to treat a wide range of diseases and particularly symptoms related to malaria. Cepharanthine (CEP) is an alkaloid isolated from this plant with potential innovative antiplasmodial activity. The analysis of interactions between antiplasmodial drugs is necessary to develop new drugs combinations to prevent de novo emergence of resistance. The objective of this study was to evaluate the anti-malarial activity of CEP in combination with usual anti-malarial compounds, both in vitro and in vivo.MethodsA fixed ratio method using the isotopic micro test was performed on the chloroquine-resistant plasmodial strain W2 to build isobolograms from eight CEP-based combinations with standard anti-malarial drugs. The efficacy of two combinations was then evaluated in the BALB/c mouse infected with Plasmodium berghei ANKA strain.ResultsIn vitro, efficiency gains were observed when CEP was combined with chloroquine (CQ), lumefantrine (LUM), atovaquone (ATO), piperaquine (PPQ) and particularly monodesethylamodiaquine (MdAQ), whereas an antagonistic interaction was observed with dihydroartemisinin (DHA) and mefloquine (MQ). In vivo, the combination of CEP with CQ or amodiaquine (AQ) improved significantly the survival of mice and extended the delay for parasitic recrudescence.ConclusionAll these observations suggest that CEP could be an interesting lead compound in the development of a combination therapy against malaria.

Early treatment failure during treatment of Plasmodium falciparum malaria with atovaquone-proguanil in the Republic of Ivory Coast

The increased spread of drug-resistant malaria highlights the need for alternative drugs for treatment and chemoprophylaxis. The combination of atovaquone‐proguanil (Malarone®) has shown high efficacy against Plasmodium falciparum with only mild side-effects. Treatment failures have been attributed to suboptimal dosages or to parasite resistance resulting from a point mutation in the cytochrome b gene. In this paper, a case of early treatment failure was reported in a patient treated with atovaquone-proguanil; this failure was not associated with a mutation in the parasite cytochrome b gene, with impaired drug bioavailability, or with re-infection.

Ethnobotany, phytochemistry and pharmacology of Stephania rotunda Lour.

ETHNOPHARMACOLOGICAL RELEVANCE Stephania rotunda Lour. (Menispermaceae) is an important traditional medicinal plant that is grown in Southeast Asia. The stems, leaves, and tubers have been used in the Cambodian, Lao, Indian and Vietnamese folk medicine systems for years to treat a wide range of ailments, including asthma, headache, fever, and diarrhoea. AIM OF THE REVIEW To provide an up-to-date, comprehensive overview and analysis of the ethnobotany, phytochemistry, and pharmacology of Stephania rotunda for its potential benefits in human health, as well as to assess the scientific evidence of traditional use and provide a basis for future research directions. MATERIAL AND METHODS Peer-reviewed articles on Stephania rotunda were acquired via an electronic search of the major scientific databases (Pubmed, Google Scholar, and ScienceDirect). Data were collected from scientific journals, theses, and books. RESULTS The traditional uses of Stephania rotunda were recorded in countries throughout Southeast Asia (Cambodia, Vietnam, Laos, and India). Different parts of Stephania rotunda were used in traditional medicine to treat about twenty health disorders. Phytochemical analyses identified forty alkaloids. The roots primarily contain l-tetrahydropalmatine (l-THP), whereas the tubers contain cepharanthine and xylopinine. Furthermore, the chemical composition differs from one region to another and according to the harvest period. The alkaloids exhibited approximately ten different pharmacological activities. The main pharmacological activities of Stephania rotunda alkaloids are antiplasmodial, anticancer, and immunomodulatory effects. Sinomenine, cepharanthine, and l-stepholidine are the most promising components and have been tested in humans. The pharmacokinetic parameters have been studied for seven compounds, including the three most promising compounds. The toxicity has been evaluated for liriodenine, roemerine, cycleanine, l-tetrahydropalmatine, and oxostephanine. CONCLUSION Stephania rotunda is traditionally used for the treatment of a wide range of ailments. Pharmacological investigations have validated different uses of Stephania rotunda in folk medicine. The present review highlights the three most promising compounds of Stephania rotunda, which could constitute potential leads in various medicinal fields, including malaria and cancer.

Quinine-resistant malaria in traveler returning from French Guiana, 2010.

To the Editor: Resistance of Plasmodium falciparum to antimalarial drugs is one of the most worrying problems in tropical medicine. For P. falciparum malaria acquired in French Guiana, the combination of quinine and doxycycline is one of the first-line recommended treatments (1). Since 1996, only 2 treatment failures with quinine have been reported from that country (2). An elevated 50% inhibitory concentration (IC50), classified as in vitro quinine resistance, was reported for 17% of 32 P. falciparum isolates obtained during 1983–1987 in French Guiana (3). Throughout 1994–2005, isolates were susceptible to quinine, with a mean IC50 <200 nmol/L (4). We report quinine treatment failure in a 35-year-old man who was infected during a 3-month stay in Saul, a rural area of French Guiana. The patient did not use antivectorial or antimalarial prophylaxis. The patient sought treatment with fever 4 days after returning to France on June 22, 2010 (day 0), and a diagnosis of P. falciparum malaria was made on the basis of results of a rapid diagnostic test performed by a private medical laboratory. The man, who weighed 58 kg, was treated as an outpatient with 500 mg of quinine to be taken orally 3×/d for 7 days; he did not receive doxycycline. He was admitted to the Laveran Military Teaching Hospital in Marseille on July 15 (day 24 and first day of recrudescence) for uncomplicated malaria with a P. falciparum parasitemia level of 4%. He was given artemether, 80 mg/d, by intramuscular injection for 3 days. Blood samples taken on day 27 (third day of recrudescence) and day 52 (4 weeks of recrudescence) were negative for P. falciparum. In vitro testing of drug susceptibility was performed by the standard 42-hour 3H-hypoxanthine uptake inhibition method (5). We assessed susceptibility to 11 antimalarial drugs on the fresh isolate and after culture adaptation (Table). The laboratory-adapted strain 3D7, tested 3× on the same batch of plates, was used as reference. The strain isolated from the blood sample on day 24 (first day of the recrudescence) showed reduced susceptibility to quinine (1,019 nmol/L), chloroquine (427 nmol/L), and monodesethylamodiaquine (157 nmol/L). The isolate was susceptible to all other antimalarial drugs tested. We assessed gene polymorphisms of pfcrt (P. falciparum chloroquine resistance transporter), pfmdr1 (P. falciparum multidrug resistance 1 protein), and pfnhe-1 (P. falciparum Na+/H+ exporter 1); the copy number of pfmdr1 involved in quinoline resistance; and gene polymorphisms of dhfr (dihydrofolate reductase, involved in proguanil or pyrimethamine resistance), dhps (dihydropteroate synthetase, involved in sulfadoxine resistance), and cytB (cytochrome B, involved in atovaquone resistance) (6). Table In vitro susceptibility to standard antimalarial drugs of a fresh isolate of Plasmodium falciparum and after culture adaptation in comparison with P. falciparum 3D7 clone tested with the same plate batches* The pfnhe ms4760 microsatellite showed a profile 3, with 1 repeat of DNNND and 2 repeats of DDDNHNDNHNN. Studies of the pfnhe-1 polymorphism of worldwide culture-adapted isolates showed that increased numbers of DNNND were associated with decreased quinine susceptibility (7). Association of 2 repeats of DNNND and a high quinine IC50 value was found in a case of clinical failure of quinine in a traveler returning from Senegal (8). Reinfection was excluded because the patient had stayed in mainland France since his return. The patient reported that he took the quinine as instructed. We report here a clinical and parasitologic failure of quinine treatment associated with high IC50 but not linked with the ms4760 pfnhe-1 profile involved with quinine in vitro reduced susceptibility. A hypothesis that may explain our data is that unlike previous studies (7), in which the less susceptible strains originated from Asia, this isolate came from South America. The profile associated with quinine resistance for chloroquine resistance and pfcrt genotypes could be different in the 3 malaria-endemic continents. There are no data on ms4760 pfnhe-1 of P. falciparum isolates from South America. In another recent study (9), a multivariate analysis performed on 83 clinical isolates from Madagascar and 13 African countries did not confirm this association between quinine susceptibility and pfnhe-1 microsatellite polymorphisms. The pfcrt gene had a point mutation on codon 76 (76T) and pfmdr1 on codons 184F, 1034C, 1042D, and 1246Y. These data are in agreement with those from previous studies that showed the mutation 76T in the pfcrt gene led to decreased susceptibility to chloroquine, amodiaquine, and quinine. The isolate had only 1 copy of pfmdr1. The data on mutations and copy number of pfmdr1 are consistent with data in Brazil (10). Nevertheless, the lack of gene amplification and specific point mutations in pfmdr1 were not associated with decreased in vitro susceptibility of quinine. dhfr and dhps genes had a 5-mutation haplotype, 51I C59 108N I164-S436 437G 540E 581G A613, which suggested in vitro resistance to proguanil, pyrimethamine, and sulfadoxine. This case confirms the need to always add doxycycline to quinine for treatment of P. falciparum malaria acquired in French Guiana as well as other parts of South America.

High-performance liquid chromatographic method for the quantification of Mitragyna inermis alkaloids in order to perform pharmacokinetic studies.

In Africa, Mitragyna inermis (Willd.) O. Kuntze (Rubiaceae) is commonly used in traditional medicine to treat malaria. Antimalarial activity is mostly due to the hydromethanolic extract of M. inermis leaves and especially to the main alkaloids, uncarine D and isorhynchophilline. In the present study, we describe for the first time an HPLC method for the simultaneous quantification of uncarine D and isorhynchophylline in biological matrices. SPE was used to extract the components and the internal standard naphthalene from human and pig plasma samples. Chromatographic separation was performed on a C-18 reversed column at a flow rate of 1 mL/min, using methanol-phosphate buffer (10:90, pH 7), as a mobile phase. Good linearity was observed over the concentration ranges of 0.0662-3.31 microg/mL for uncarine D and 0.0476-2.38 microg/mL for isorynchophylline. The precision was less than 12% and the accuracy was from 86 to 107% without any discrepancy between the two species. Uncarine D and isorhynchophylline recoveries were over 80%. These results allowed the quantification of both uncarine D and isorhynchophylline in pig plasma after intravenous administration of M. inermis extract.

Biologically active carbazole derivatives: focus on oxazinocarbazoles and related compounds

Abstract Four series of carbazole derivatives, including N-substituted-hydroxycarbazoles, oxazinocarbazoles, isoxazolocarbazolequinones, and pyridocarbazolequinones, were studied using diverse biological test methods such as a CE-based assay for CK2 activity measurement, a cytotoxicity assay with IPC-81 cell line, determination of MIC of carbazole derivatives as antibacterial agents, a Plasmodium falciparum susceptibility assay, and an ABCG2-mediated mitoxantrone assay. Two oxazinocarbazoles Ib and Ig showed CK2 inhibition with IC50 = 8.7 and 14.0 µM, respectively. Further chemical syntheses were realized and the 7-isopropyl oxazinocarbazole derivative 2 displayed a stronger activity against CK2 (IC50 = 1.40 µM). Oxazinocarbazoles Ib, Ig, and 2 were then tested against IPC-81 leukemia cells and showed the ability to induce leukemia cell death with IC50 values between 57 and 62 μM. Further investigations were also reported on antibacterial and antiplasmodial activities. No significant inhibitory activity on ABCG2 efflux pump was detected.

Quantitative Analysis of Cepharanthine in Plasma Based on Semiautomatic Microextraction by Packed Sorbent Combined with Liquid Chromatography

The spread of Plasmodium falciparum resistance toward most of the used drugs requires new antimalarial compounds. Taking advantage of the biodiversity, the ethnopharmacological approach opens the way for the discovery and the characterization of potent original molecules. Previous works led to the selection of a bisbenzylisoquinoline, cepharanthine, extracted from Stephania rotunda, which is mainly present in Cambodia. A sensitive and selective liquid chromatography method has been developed for the determination of cepharanthine in mouse plasma. The method involved a semiautomated microextraction by packed sorbent (MEPS) using 4 mg of solid phase silica-C8 sorbent. LC separation was performed on a Kinetex XB-C18 column (2.6 µm) with a mobile phase of acetonitrile containing formic acid and 10 mM ammonium formate buffer pH 3.5. Data were acquired at 282 nm with a diode array detector. The drug/internal standard peak area ratios were linked via linear relationships to plasma concentrations (75–2,000 ng/mL). Precision was below 5% and accuracy was 99.0–102%. Extraction recovery of cepharanthine was 56–58%. The method was successfully used to determine the pharmacokinetic profile of cepharanthine in healthy and Plasmodium berghei infected mice. The infection did not impact pharmacokinetic parameters of cepharanthine.