artelinic-acid and artenimol

Three artemisinin antimalarials, arteether (AE), artesunate (AS), and artelinate (AL) were evaluated in rats using an auditory discrimination task (ADT) and neurohistology. After rats were trained on the ADT, equimolar doses of AE (25 mg/kg, in sesame oil, n=6), AS (31 mg/kg, in sodium carbonate, n=6), and AL (36 mg/kg, in saline, n=6), or vehicle (sodium carbonate, n=6) were administered (IM) for 7 consecutive days. Behavioral performance was evaluated, during daily sessions, before, during, and after administration. Histological evaluation of the brains was performed using thionine staining, and damaged cells were counted in specific brainstem nuclei of all rats. Behavioral performance was not significantly affected in any rats treated with AS, AL, or vehicle. Furthermore, histological examination of the brains of rats treated with AS, AL, and vehicle did not show damage. In stark contrast, all rats treated with AE showed a progressive and severe decline in performance on the ADT. The deficit was characterized by decreases in accuracy, increases in response time and, eventually, response suppression. When performance on the ADT was suppressed, rats also showed gross behavioral signs of toxicity that included tremor, gait disturbances, and lethargy. Subsequent histological assessment of AE-treated rats revealed marked damage in the brainstem nuclei, ruber, superior olive, trapezoideus, and inferior vestibular. The damage included chromatolysis, necrosis, and gliosis. These results demonstrate distinct differences in the ability of artemisinins to produce neurotoxicity. Further research is needed to uncover pharmacokinetic and metabolic differences in artemisinins that may predict neurotoxic potential.

Topics: Animals; Antimalarials; Artemisinins; Artesunate; Behavior, Animal; Brain; Brain Stem; Discrimination Learning; Male; Rats; Rats, Sprague-Dawley; Sesquiterpenes

1. Artelinic acid (AL), a water-soluble artemisinin analogue for treatment of multidrug resistant malaria, is metabolized to the active metabolite dihydroqinghaosu (DQHS) solely by CYP3A4/5. Although AL is not metabolized by CYP2C9, it does inhibit diclofenac 4-hydroxylase activity with an IC50 = 115 microM. Interestingly, AL activates CYP2D6-mediated bufuralol metabolism in human liver microsomes but not recombinant CYP2D6-Val by approximately 30% at AL concentrations up to 100 microM. 2. In human liver microsomes, AL is metabolized to DQHS with a Km = 157 +/- 44 microM and Vmax = 0.77 +/- 0.56 nmol DQHS/min/mg protein. Human recombinant CYP3A4 catalysed the conversion of AL to DQHS with a Km = 102 +/- 23 microM and a Vmax = 1.96 +/- 0.38 nmol DQHS/min/nmol P450. The kinetic parameters (Km and Vmax) for DQHS formation from CYP3A5 were 189 +/- 19 microM and 3.60 +/- 0.42 nmol DQHS/min/nmol P450 respectively. 3. Inhibition studies suggest that azole antifungals and calcium channel blockers may present clinically significant drug drug interactions. In human liver microsomes, ketoconazole and miconazole were potent competitive inhibitors of DQHS formation with a Ki = 0.028 and 0.124 microM respectively. Verapamil is a non-competitive inhibitor of DQHS formation in human liver microsomes with a Ki = 15 microM.

Topics: Adult; Aged; Antifungal Agents; Antimalarials; Artemisinins; Aryl Hydrocarbon Hydroxylases; Cytochrome P-450 CYP2D6; Cytochrome P-450 CYP3A; Cytochrome P-450 Enzyme System; Drug Combinations; Drug Interactions; Drugs, Chinese Herbal; Enzyme Inhibitors; Female; Glycyrrhiza; Humans; Inactivation, Metabolic; Inhibitory Concentration 50; Isoenzymes; Ketoconazole; Liver; Male; Miconazole; Microsomes, Liver; Middle Aged; Oxidoreductases, N-Demethylating; Paeonia; Quinidine; Recombinant Proteins; Sesquiterpenes; Sulfaphenazole; Troleandomycin; Vasodilator Agents; Verapamil

We have produced monoclonal antibodies against artelinic acid and investigated the reactivity with artemisinin drugs and metabolites. Antibody F170-10 is fairly specific for artelinic acid but does bind artemisinin and artemether (3-5% cross-reactivity). Dihydroartemisinin, artesunate, and metabolites of artemisinin showed less reactivity. With this antibody, an inhibition ELISA has been set up to detect artemisinin compounds in urine. In healthy subjects who received a single oral dose of artemisinin, artemether, artesunate or dihydroartemisinin, ELISA reactivity in urine was found. This reactivity in urine paralleled the plasma concentrations of artemether and dihydroartemisinin. The results show that this immunoassay for artelinic acid can be used to detect artemisinin compounds in urine for about 8 hr after intake. With a more sensitive test, this simple method as a urine dipstick may be become useful for drug use and compliance studies in malaria-endemic areas where the artemisinin derivatives are increasingly used.

Topics: Adult; Antibodies, Monoclonal; Antimalarials; Artemisinins; Artesunate; Cross Reactions; Enzyme-Linked Immunosorbent Assay; Humans; Sesquiterpenes

The pharmacokinetics and bioavailability of dihydroartemisinin (DQHS), artemether (AM), arteether (AE), artesunic acid (AS) and artelinic acid (AL) have been investigated in rats after single intravenous, intramuscular and intragastric doses of 10 mg kg(-1). Plasma was separated from blood samples collected at different times after dosing and analysed for parent drug. Plasma samples from rats dosed with AM, AE, AS and AL were also analysed for DQHS which is known to be an active metabolite of these compounds. Plasma levels of all parent compounds decreased biexponentially and were a reasonable fit to a two-compartment open model. The resulting pharmacokinetic parameter estimates were substantially different not only between drugs but also between routes of administration for the same drug. After intravenous injection the highest plasma level was obtained with AL, followed by DQHS, AM, AE and AS. This resulted in the lowest steady-state volume of distribution (0.39 L) for AL, increasing thereafter for DQHS (0.50 L), AM (0.67 L), AE (0.72 L) and AS (0.87 L). Clearance of AL (21-41 mL min(-1) kg(-1)) was slower than that of the other drugs for all three routes of administration (DQHS, 55-64 mL min(-1) kg(-1); AM, 91-92 mL min(-1) kg(-1); AS, 191-240 mL min(-1) kg(-1); AE, 200-323 mL min(-1) kg(-1)). In addition the terminal half-life after intravenous dosing was longest for AL (1.35 h), followed by DQHS (0.95 h), AM (0.53 h), AE (0.45 h) and AS (0.35 h). Bioavailability after intramuscular injection was highest for AS (105%), followed by AL (95%) and DQHS (85%). The low bioavailability of AM (54%) and AE (34%) is probably the result of slow, prolonged absorption of the sesame-oil formulation from the injection site. After oral administration, low bioavailability (19-35%) was observed for all five drugs. In-vivo AM, AE, AS and AL were converted to DQHS to different extents; the ranking order of percentage of total dose converted to DQHS was AS (25.3-72.7), then AE (3.4-15.9), AM (3.7-12.4) and AL (1.0-4.3). The same ranking order was obtained for all formulations and routes of administration. The drug with the highest percentage conversion to DQHS was artesunic acid. Because DQHS has significant antimalarial activity, relatively low DQHS production could still contribute significantly to the antimalarial efficacy of these drugs. This is the first time the pharmacokinetics, bioavailability and conversion to DQHS of these drugs have been directly compared after

Topics: Absorption; Animals; Antimalarials; Area Under Curve; Artemether; Artemisinins; Biological Availability; Bridged Bicyclo Compounds, Heterocyclic; Male; Rats; Rats, Sprague-Dawley; Sesquiterpenes; Succinates

To search for water soluble dihydroartemisinin derivatives with higher efficacy and longer plasma half-life than artesunic or artelinic acid, a series of new stereoisomers of 4-(p-substituted phenyl)-4(R or S)-[10(alpha or beta)-dihydroartemisininoxy]butyric acids were synthesized as new potential antimalarial agents. Two approaches were taken in the design of these new molecules in an attempt to (a) increase the lipophilicity of the molecule and (b) decrease the rate of oxidative dealkylation of the target compounds. The new compounds showed a 2-10-fold increase in in vitro antimalarial activity against D-6 and W-2 clones of Plasmodium falciparum than artemisinin or artelinic acid. R-diastereomers are, in general, more potent than the corresponding S-diastereomers. p-Chlorophenyl and p-bromophenyl derivatives showed in vivo oral antimalarial activity against P. berghei (with 3/8 cured) superior to that of artelinic acid (1/8 cured), whereas p-fluorophenyl and p-methoxyphenyl analogs demonstrated activity only comparable (1/8 cured) to that of artelinic acid at the same dosage level (64 mg/kg twice a day). The in vivo antimalarial activity of these new compounds correlates with their SD50 (50% parasitemia suppression dose). The biological results suggested that an electronic effect, besides the lipophylicity, may play a role in determining the efficacy of this class of compounds.

Topics: Animals; Antimalarials; Artemisinins; Drug Design; Female; Magnetic Resonance Spectroscopy; Malaria; Mice; Molecular Conformation; Molecular Structure; Parasitemia; Plasmodium berghei; Plasmodium falciparum; Sesquiterpenes; Solubility

In addition to artelinic acid, which was demonstrated previously to possess good prophylactic as well as curative antimalarial activity against Plasmodium berghei by transdermal administration, seven artemisinin derivatives in a gel formulation were assessed for their antimalarial activities in this study. Artemisinin, the parent compound of the series, showed moderate prophylactic but poor curative activity. Although methyl artelinate was more active against P. berghei than artelinic acid and sodium artelinate by subcutaneous injection, its transdermal curative and prophylactic activity was only comparable with or weaker than that of artelinic acid. Conversely, both dihydroartemisinin trimethylsilyl ether and dehydrodihydroartemisinin showed weaker antimalarial activity than artelinic acid by the subcutaneous route, yet exhibited comparable activity by transdermal administration. Artemether, a prodrug of dihydroartemisinin, is as effective as the parent dihydroartemisinin, and both compounds were the most potent agents among the compounds studied, with total prophylactic and curative doses of 30 mg/kg and 60 mg/kg, respectively. Complete absorption of dihydroartemisinin appears to occur within 5 min after application. In general, we found that the prophylactic dose is about half that of the curative dose under the protocols used in this study. This novel drug delivery system may be an easy and safe way to administer artemisinin-type antimalarials and also a good alternative dosage form for active compounds with solubility problems.

Topics: Administration, Cutaneous; Animals; Antimalarials; Artemether; Artemisinins; Gels; Malaria; Mice; Plasmodium berghei; Sesquiterpenes; Structure-Activity Relationship

1. In this communication, induction of hydrogen peroxide production by the semisynthetic antimalarial drugs of the artemisinin class (beta-arteether, beta-artelinic acid and dihydroartemisinin) in rat liver microsomes, is reported. 2. Endogenous, NADPH-dependent, production of hydrogen peroxide in rat liver microsomes was enhanced in the presence of arteether and artelinic acid, but not in the presence of dihydroartemisinin. 3. NADPH-dependent metabolism of arteether and artelinic acid was closely coupled to the drug-induced production of hydrogen peroxide. 4. The redox cycle of cytochrome P-450 was presented, which describes satisfactorily both the endogenous and the drug-assisted hydrogen peroxide production in rat liver microsomes; also, the rate-limiting step of the cycle was identified.

Topics: Animals; Antimalarials; Artemisinins; Hydrogen Peroxide; Kinetics; Male; Microsomes, Liver; NADP; Rats; Rats, Inbred Strains; Sesquiterpenes

1. In this communication, metabolism of the semisynthetic antimalarial drugs of the artemisinin class (beta-arteether, beta-artelinic acid and dihydroartemisinin) in rat liver microsomes, is reported. 2. Dihydroartemisinin was the major early metabolite of arteether (57%) and artelinic acid (80%); in addition, arteether was hydroxylated in the positions 9 alpha- and 2 alpha- of the molecule. 3. Dihydroartemisinin was further metabolized by extensive hydroxylation of its molecule; we were able to identify four hydroxylated derivatives of DQHS, but not the exact positions of the hydroxyl groups. 4. The rates of NADPH-supported metabolism of arteether, artelinic acid and dihydroartemisinin in rat liver microsomes were: 4.0, 2.5 and 1.3 nmol/min/mg of microsomal protein, respectively. 5. The apparent affinity constants of arteether and artelinic acid for the microsomal metabolizing system, calculated from the rates of product formation, were 0.54 mM and 0.33 mM (for arteether) and 0.11 mM (for artelinic acid), respectively. The appearance of two affinity constants indicated that arteether was metabolized by two different isoenzymes of cytochrome P-450 in rat liver microsomes.

Topics: Animals; Antimalarials; Artemisinins; Chromatography, High Pressure Liquid; Chromatography, Liquid; Kinetics; Liver; Male; Mass Spectrometry; Microsomes, Liver; Rats; Rats, Inbred Strains; Sesquiterpenes