Similar vertical transmission rates of dengue and chikungunya viruses in a transgenic and a non-transformed Aedes aegypti (L.) laboratory strain

The increase of the burden of dengue and chikungunya and the relative failure of traditional vector control strategies have highlighted the need to develop new control methods. RIDL-SIT, a vector control method based on the release of engineered male mosquitoes, has shown promising results from field trials conducted in the Cayman Islands and Brazil. In large scale use, a small proportion of females might be released along with the males. Such females are potential virus vectors; here we investigate the vertical transmission of dengue and chikungunya of homozygous OX513A females.We provided females of OX513A-My1 and a wild type comparator strain with blood meals artificially infected with dengue serotype 1, 2, 3, 4 or chikungunya viruses. For 14 days post-feeding, eggs laid by females were collected. Larvae and their mothers were first tested by qRT-PCR, then by inoculation on cell cultures to search for infectious viral particles. We found no significant difference between the minimum infection rate of OX513A-My1 and wild type females. We also discussed the potential number of females being released, a fraction of the female wild population. Consequently, we conclude that there are no evidence that OX513A-My females, if released into the environment, would cause more harm than their wild counterparts.

Evaluation of phenolic content and antioxidant potency in various parts of Cassia auriculata L.: a traditionally valued plant

Presence of polyphenolic content in various part of the plant exhibit wide pharmacological activities including antioxidant activity. The present study was designed to evaluate the phenolic contents (total phenols, flavonoid and tannins) and antioxidant properties of ethanolic extracts of flower, leaf, pod, bark and root obtained from Cassia auriculata. Ethanolic extracts of various parts of C. auriculata obtained by sonication extraction techniques are studied for their phenolic contents and DPPH (2,2-diphenyl-1-picrylhydrazine) radical scavenging assay as well as total antioxidant assays using UV visible spectrophotometer. Among the various parts of the plant studied, bark showed significant content of phenolics, flavonoids and tannins followed by the root, leaf, flower and pod. Even bark extract exhibited highest antioxidant capacity in DPPH assay followed by root, leaf, flower and pod with a value of 766.7, 679.3, 644.9, 572.5 and 474.7 mg vitamin C equivalent antioxidant capacity (mg VCEAC)/sample, respectively. In addition, mg VCEAC values obtained from the total antioxidant assay was in the increasing order of bark > root > leaf > flower > pod. Moreover, a strong correlation was also found between phenolic contents and antioxidant values indicating their influence in the found antioxidant activity, hence the bark extract can be employed as an ideal candidate for herbal based pharmaceutical product. Results of the present study also emphasize variation in the chemical composition as well as biological activity ensuring the importance of proper selection of particular part of the plant to evaluate their therapeutic potency.

Inhibitory effect of mitragynine on human cytochrome P450 enzyme activities

Context:

To date, many findings reveal that most of the modern drugs have the ability to interact with herbal drugs.

Aims:

This study was conducted to determine the inhibitory effects of mitragynine on cytochrome P450 2C9, 2D6 and 3A4 activities.

Methods and Material:

The in vitro study was conducted using a high-throughput luminescence assay.

Statistical Analysis:

Statistical analysis was conducted using one-way ANOVA and Dunnett's test with P < 0.05 vs. control. The IC₅₀ values were calculated using the GraphPad Prism^® 5 (Version 5.01, GraphPad Software, Inc., USA).

Results:

Assessment using recombinant enzymes showed that mitragynine gave the strongest inhibitory effect on CYP2D6 with an IC₅₀ value of 0.45±0.33 mM, followed by CYP2C9 and CYP3A4 with IC₅₀ values of 9.70±4.80 and 41.32±6.74 μM respectively. Positive inhibitors appropriate for CYP2C9, CYP2D6, and CYP3A4 which are sulfaphenazole, quinidine and ketoconazole were used respectively. V_max values of CYP2C9, CYP2D6 and CYP3A4 were 0.0005, 0.01155 and 0.0137 μM luciferin formed/pmol/min respectively. K_m values of CYP2C9, CYP2D6, and CYP3A4 were 32.65, 56.01, and 103.30 μM respectively. Mitragynine noncompetitively inhibits CYP2C9 and CYP2D6 activities with the K_i values of 61.48 and 12.86 μM respectively. On the other hand, mitragynine inhibits CYP3A4 competitively with a K_i value of 379.18 μM.

Conclusions:

The findings of this study reveal that mitragynine might inhibit cytochrome P450 enzyme activities, specifically CYP2D6. Therefore, administration of mitragynine together with herbal or modern drugs which follow the same metabolic pathway may contribute to herb-drug interactions.

The free radical scavenging and antioxidant activities of pod and seed extract of Clitoria fairchildiana (Howard)- an underutilized legume

We evaluated the phenolic content and antioxidant capacities of pod and seed extracts (in methanol, ethanol, and water) of an underutilized legume, Clitoria fairchildiana (Howard). The antioxidant capacity of the extracts was determined using the ferric reducing antioxidant potential assay, and the free radical-scavenging capacity was evaluated using 2,2-diphenyl-1-picrylhydrazyl radical-scavenging and ABTS assays. In addition, the total flavonoids, flavonols, and tannin contents were also determined. Overall, the methanol extracts of the pod contained high concentration of phenolics and showed high antioxidant capacities compared to seed extracts. In addition, a positive correlation was found between total phenol and tannin versus antioxidant capacity. Results of the present study indicate pods and seeds of C. fairchildiana to possess rich amount of natural antioxidants, and can be further explored for their possible use as a natural additive in food or in pharmaceutical industries.

Analgesic activity, toxicity study and phytochemical screening of standardized Cinnomomum iners leaves methanolic extract

Cinnomomum iners standardized leaves methanolic extract (CSLE) was subjected to analgesic, toxicity and phytochemical studies. The analgesic activity of CSLE was evaluated using formalin, hot plate and tail flick tests at doses of 100, 200 and 500 mg/kg. CSLE showed significant activity (P < 0.05) in the formalin model (late phase) on the rats at doses of 200 and 500 mg/kg. However, CSLE did not show activity in the hot plate and tail flick tests. The results obtained suggest that CSLE acts peripherally to relieve pain. For the toxicity study, CSLE was orally administered to the Swiss albino mice according to the Organization for Economic Co-Operation and Development (OECD) guideline 423. There was no lethality or toxic symptoms observed for all the tested doses throughout the 14-day period. Phytochemical screening of CSLE showed the presence of cardiac glycoside, flavonoid, polyphenol, saponin, sugar, tannin and terpenoid.

Influence of sonication on the phenolic content and antioxidant activity of Terminalia catappa L. leaves

Aim:

This study was designed to evaluate the phenolic content and antioxidant activity of ethanolic extracts from T. catappa leaves obtained by different intervals of sonication.

Methods:

Three commonly used methods were followed to evaluate phenolic content and four in vitro methods like 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) radical scavenging assay, ferric reducing antioxidant potency (FRAP), and total antioxidant capacity assays for measuring the antioxidant activities. Antioxidant values of these assays were expressed in terms of milligrams vitamin C equivalent (VCE) antioxidant activities.

Results:

This study showed that extract obtained with 40 minutes of sonication possessed significant (P < 0.05) polyphenolic contents compared to 20 and 60 minutes sonication and control (24 hour maceration). Moreover, sonication of T. catappa leaf above 40 minutes was found to be unsuitable for extracting out phenolic contents. Even the results of antioxidant assays showed that 40 minutes of the sonicated extract exhibited significant (P < 0.05) VCE values compared to extracts obtained at different intervals of sonication and control.

Conclusions:

In sonication extraction method 40 minutes is an ideal time to obtain extract enriched with high polyphenolic content with good antioxidant activity from T. catappa leaves.

Influence of sonication treatments and extraction solvents on the phenolics and antioxidants in star fruits

The present study was conducted to examine the effects of sonication treatments (time intervals of 0, 15, 30, 45 and 60 min.) on phenolics and other antioxidant compounds in starfruits extracted in methanol and water. Overall, methanolic extracts exhibited significantly higher extractability, percentage inhibition of DPPH radicals, ferric reducing antioxidant property (FRAP) value, antioxidant capacity, flavonoids, total phenolics and tannins (p < 0.05) compared to control (0 min) and aqueous extracts. Methanolic extract obtained after 30 min of sonication proved to be the best treatment with regard to various parameters evaluated. Results of the present study clearly indicated sonication treatments to be effective in enhancing the antioxidant compounds in starfruit extracts and could be further explored for commercial purposes to benefit the consumers.

In vitro and in vivo anticandidal activity of Swietenia mahogani methanolic seed extract

Swietenia mahogani crude methanolic (SMCM) seed extract was investigated for the antifungal activity against Candida albicans which has not been evaluated previously. The antifungal activity was evaluated against C. albicans via disk diffusion, minimum inhibition concentration (MIC), scanning electron microscope (SEM), transmission electron microscope (TEM) and time killing profile. The MIC value of SMCM seed extract is 12.5 mg/ml. The SEM and TEM findings showed there is morphological changes and cytological destruction of C. albicans at the MIC value. Animal model was used to evaluate the in vivo antifungal activity of SMCM seed extract. The colony forming unit (CFU) were calculated per gram of kidney sample and per ml of blood sample respectively for control, curative and ketaconazole treated groups. There was significant reduction for the CFU/ml of blood and CFU/g of kidney. This indicated that the extract was observed to be effective against C. albicans in vitro and in vivo conditions.

Acute toxicity study of the standardized methanolic extract of Mitragyna speciosa Korth in rodent

ETHNOPHARMACOLOGICAL RELEVANCE

Mitragyna speciosa Korth (ketum) is widely used in Malaysia as a medicinal agent for treating diarrhea, worm infestations and also acts as an analgesic and antipyretic.

AIM

The aim of the study is to determine the acute toxicity of Mitragyna speciosa Korth standardized methanol extract in vivo in 4-weeks-old Sprague-Dawley rats.

METHODOLOGY

Rats were orally administrated single dose of 100, 500 and 1000 mg/kg Mitragyna speciosa Korth standardized methanol extract and the control group received 430 mg/kg of morphine orally. There were 10 rats in each group. All animals were sacrificed after 14 days of treatment. Eight parameters were tested: cage side observation, body weight measurement, food and water consumption, blood pressure, absolute and relative organ weight, hematology, biochemical analysis and histopathology, to look for evidence of toxicity.

RESULT

No mortality was noted after 14 days of treatment. In general, behavior, food and water consumption, hematological studies and organ weights showed no significant changes. The standardized methanol extraction of Mitragyna speciosa Korth increased rat blood pressure (systolic: 147.4+/-1.01, 131.64+/-4.94 and 137.8+/-4.46) after an hour of 100, 500 and 1000 mg/kg doses, respectively. Biochemical studies showed significant elevation of ALT, AST, albumin, triglycerides, cholesterol and albumin (p>0.05), at all levels of doses. But, nephrotoxicity evidenced by elevated creatinine was seen only at a dose of 1000 mg/kg. Histological examination showed congestion of sinusoids, hemorrhage hepatocytes, fatty change, centrilobular necrosis and increased number of Kuppfer cells in the liver of all Mitragyna speciosa Korth standardized methanol extract treated groups.

CONCLUSION

Oral administration of standardized methanolic extraction of Mitragyna speciosa Korth resulted in increasing rat blood pressure after an hour of drug administration. The highest dose of extract also induced acute severe hepatotoxicity and mild nephrotoxicity. However, Mitragyna speciosa Korth shows no effects on body weight, food and water consumption, absolute and relative organ weight and also hematology parameters.

Chemical constituents and in vitro anticancer activity of Typhonium flagelliforme (Araceae)

AIM OF THE STUDY

Typhonium flagelliforme is an indigenous plant of Malaysia and is used by the local communities to treat cancer. This study aims to identify the chemical constituents of Typhonium flagelliforme particularly those which have antiproliferative properties towards human cancer cell lines.

MATERIALS AND METHODS

Purification of the chemical constituents by various chromatographic procedures was guided by the antiproliferative activity. Identification of the chemical constituents was carried out by various spectroscopic techniques including high resolution MS and NMR. The antiproliferative activity was assayed using MTT on NCI-H23 (lung cancer) and HS578T (breast cancer) cell lines. Microscopic observation and DeadEnd colourimetric TUNEL assay was used to identify the apoptotic mode of cell death.

RESULTS AND CONCLUSION

Four pheophorbide related compounds, namely pheophorbide-a, pheophorbide-a', pyropheophorbide-a and methyl pyropheophorbide-a were identified in the most active fraction, D/F19. These constituents exhibited antiproliferative activity against cancer cells and the activity increased following photoactivation. However, the greater antiproliferative activity exhibited by D/F19 itself compared to the pheophorbides and its other subfractions suggests some form of synergistic action between the constituents. The inhibitory effect of D/F19 and the pheophorbides was apoptotic in the absence of light. Other chemical constituents that have been identified in this study include hexadecanoic acid, oleic acid, linoleic acid, linolenic acid, campesterol, stigmasterol and beta-sitosterol. Most of the chemical constituents identified in this plant have not been reported previously.

Phytochemical and antimicrobial activity of Swietenia mahagoni crude methanolic seed extract

The present study was designed to evaluate the antibacterial activities of Swietenia mahagoni crude methanolic (SMCM) seed extract. The antimicrobial activity of the oily extract against Gram-positive, Gram-negative, yeast and fungus strains was evaluated based on the inhibition zone using disc diffusion assay, minimal inhibition concentration (MIC) and minimal bactericidal concentration (MBC) values. The crude extract was subjected to various phytochemicals analysis. The demonstrated qualitative phytochemical tests exhibited the presences of common phytocompounds including alkaloids, terpenoids, antraquinones, cardiac glycosides, saponins, and volatile oils as major active constituents. The SMCM seed extract had inhibitory effects on the growth of Candida albicans, Staphylococcus aureus, Pseudomonas aeroginosa, Streptococcus faecalis and Proteus mirabillase and illustrated MIC and MBC values ranging from 25 mg/ml to 50 mg/ml.

Effects of Clitoria ternatea leaf extract on growth and morphogenesis of Aspergillus niger

Clitoria ternatea is known for its antimicrobial activity but the antifungal effects of leaf extract on growth and morphogenesis of Aspergillus niger have not been observed. The extract showed a favorable antifungal activity against A. niger with a minimum inhibition concentration 0.8 mg/mL and minimum fungicidal concentration 1.6 mg/mL, respectively. The leaf extract exhibited considerable antifungal activity against filamentous fungi in a dose-dependent manner with 0.4 mg/mL IC50 value on hyphal growth of A. niger. The main changes observed under scanning electron microscopy after C. ternatea extract treatment were loss of cytoplasm in fungal hyphae and the hyphal wall and its diameter became markedly thinner, distorted, and resulted in cell wall disruption. In addition, conidiophore alterations were also observed when A. niger was treated with C. ternatea leaf extract.

Typhonium flagelliforme inhibits cancer cell growth in vitro and induces apoptosis: an evaluation by the bioactivity guided approach

AIM OF THE STUDY

Typhonium flagelliforme (Lodd.) Blume (Araceae) is a Malaysian plant used locally to combat cancer. In order to evaluate its antiproliferative activity in vitro and to possibly identify the active chemical constituents, a bioactivity guided study was conducted on the extracts of this plant.

MATERIALS AND METHODS

The active extracts of Typhonium flagelliforme were fractionated by flash column chromatography and each fraction was evaluated for antiproliferative activity using MTT assay. The apoptotic effect of the active fraction was determined microscopically and by using TUNEL colorimetric assay. GC-MS and NMR were used to determine the chemical constituents of this active fraction.

RESULTS

Several fractions of the hexane and dichloromethane extracts were found to inhibit the growth of NCI-H23 non-small cell lung carcinoma cell line significantly, with IC(50)<15 microg/ml. However, most of these active fractions were also found to inhibit the growth of non-tumorigenic BALB/c 3T3 mouse fibroblast cell line except for fraction 21 of the dichloromethane extract (D/F21). This particular fraction was not only less cytotoxic to the non-tumorigenic cells, where the IC(50) was 48.6 microg/ml compared to IC(50) 7.5 microg/ml for NCI-H23, but it was also found to induce apoptosis in the cancer cell line. GC-MS analysis revealed that D/F21 contains hexadecanoic acid, 1-hexadecene, phytol and a derivative of phytol. The presence of non-saturated fatty acids in this fraction was confirmed by nuclear magnetic resonance spectroscopy.

CONCLUSIONS

D/F21 was found to be the active and cancer cell line specific fraction of Typhonium flagelliforme. Its major chemical constituents had been determined spectroscopically.

An analytical method with a single extraction procedure and two separate high performance liquid chromatographic systems for the determination of artesunate, dihydroartemisinin and mefloquine in human plasma for application in clinical pharmacological studies of the drug combination

The combination of two sensitive, selective and reproducible reversed phase liquid chromatographic (RP-HPLC) methods was developed for the determination of artesunate (AS), its active metabolite dihydroartemisinin (DHA) and mefloquine (MQ) in human plasma. Solid phase extraction (SPE) of the plasma samples was carried out on Supelclean LC-18 extraction cartridges. Chromatographic separation of AS, DHA and the internal standard, artemisinin (QHS) was obtained on a Hypersil C4 column with mobile phase consisting of acetonitrile-0.05 M acetic acid adjusted to pH 5.2 with 1.0M NaOH (42:58, v/v) at the flow rate of 1.50 ml/min. The analytes were detected using an electrochemical detector operating in the reductive mode. Chromatography of MQ and the internal standard, chlorpromazine hydrochloride (CPM) was carried out on an Inertsil C8-3 column using methanol-acetonitrile-0.05 M potassium dihydrogen phosphate adjusted to pH 3.9 with 0.5% orthophosphoric acid (50:8:42, v/v/v) at a flow rate of 1.00 ml/min with ultraviolet detection at 284 nm. The mean recoveries of AS and DHA over a concentration range of 30-750 ng/0.5 ml plasma and MQ over a concentration of 75-1500 ng/0.5 ml plasma were above 80% and the accuracy ranged from 91.1 to 103.5%. The within-day coefficients of variation were 1.0-1.4% for AS, 0.4-3.4% for DHA and 0.7-1.5% for MQ. The day-to-day coefficients of variation were 1.3-7.6%, 1.8-7.8% and 2.0-3.4%, respectively. Both the lower limit of quantifications for AS and DHA were at 10 ng/0.5 ml and the lower limit of quantification for MQ was at 25 ng/0.5 ml. The limit of detections were 4 ng/0.5 ml for AS and DHA and 15 ng/0.5 ml for MQ. The method was found to be suitable for use in clinical pharmacological studies.

Development and validation of RP-HPLC-UV method for simultaneous determination of buparvaquone, atenolol, propranolol, quinidine and verapamil: A tool for the standardization of rat in situ intestinal permeability studies

A simple, sensitive and specific reversed phase high performance liquid chromatographic (RP-HPLC) method with UV detection at 251 nm was developed for simultaneous quantitation of buparvaquone (BPQ), atenolol, propranolol, quinidine and verapamil. The method was applicable in rat in situ intestinal permeability study to assess intestinal permeability of BPQ, a promising lead compound for Leishmania donovani infections. The method was validated on a C-4 column with mobile phase comprising ammonium acetate buffer (0.02 M, pH 3.5) and acetonitrile in the ratio of 30:70 (v/v) at a flow rate of 1.0 ml/min. The retention times for atenolol, quinidine, propranolol, verapamil and BPQ were 4.30, 5.96, 6.55, 7.98 and 8.54 min, respectively. The calibration curves were linear (correlation coefficient > or =0.996) in the selected range of each analyte. The method is specific and sensitive with limit of quantitation of 15 microg/ml for atenolol, 0.8 microg/ml for quinidine, 5 microg/ml for propranolol, 10 microg/ml for verapamil and 200 ng/ml for BPQ. The validated method was found to be accurate and precise in the working calibration range. Stability studies were carried out at different storage conditions and all the analytes were found to be stable. This method is simple, reliable and can be routinely used for accurate permeability characterization.

Permeability of atenolol and propranolol in the presence of dimethyl sulfoxide in rat single-pass intestinal perfusion assay with liquid chromatography/UV detection

A simple and sensitive RP-HPLC-UV method was developed and validated for simultaneous determination of atenolol and propranolol and subsequently applied to investigate the effect of dimethyl sulfoxide in rat in situ intestinal permeability studies. Atenolol (400 microm) and propranolol (100 microm) were perfused in the small intestine of anaesthetized (pentobarbitone sodium 60 mg/kg, i.p.) male Sprague-Dawley rats either in the presence (1, 3 and 5%) or in the absence of dimethyl sulfoxide. There was no significant alteration (p > 0.05) in the permeability of atenolol and propranolol, which indicated there was no effect of various concentrations of dimethyl sulfoxide (1-5%) on the membrane integrity of the rat intestinal tissues. The analytical method was validated on a C(4) column with a mobile phase comprising ammonium acetate buffer (pH 3.5, 0.02 m) and acetonitrile in the ratio of 30:70 (v/v) at a flow rate of 1.0 mL/min. The validated method was found to be accurate and precise and stability studies were carried out at different storage conditions and both analytes were found to be stable. These findings are applicable for determining the absorbability of water-insoluble drugs and new chemical entities for the purpose of classifying them in the biopharmaceutical classification system.

A new and simple solid-phase extraction method for LC determination of pyronaridine in human plasma

A new approach using a simple solid-phase extraction technique has been developed for the determination of pyronaridine (PND), an antimalarial drug, in human plasma. After extraction with C18 solid-phase sorbent, PND was analyzed using a reverse phase chromatographic method with fluorescence detection (at lambda(ex)=267 nm and lambda(em)=443 nm). The mean extraction recovery for PND was 95.2%. The coefficient of variation for intra-assay precision, inter-assay precision and accuracy was less than 10%. The quantification limit with fluorescence detection was 0.010 microg/mL plasma. The method described herein has several advantages over other published methods since it is easy to perform and rapid. It also permits reducing both, solvent use and sample preparation time. The method has been used successfully to assay plasma samples from clinical pharmacokinetic studies.

Polyvinyl chloride-based membranes for flow injection analysis of quinine in beverages

Potentiometric response characteristics were evaluated for quinine selective sensors based on a lipophilic ion-exchanger potassium tetrakis[3,5-bis(trifluoromethylphenyl)]borate (PTFB) immobilized together with plasticizing solvents in polyvinyl chloride membranes. The use of dioctyl phthalate (DOP), 2-nitrophenyl phenyl ether (NPPE), and bis(2-ethylhexyl)adipate (BEHA) plasticizers produced good quality quinine sensors that were sensitive and fast responding, and exhibited near Nernstian responses when used as batch-sensors. These membranes were further tested in a wall-jet flow-through potentiometric flow injection analysis (FIA) detector. Quinine sensors containing BEHA were the most suitable membrane, with no noticeable differences in sensitivity even after 5 h of continuous exposure to solutions. Interference by foreign species such as alkali, alkaline earth metal ions, sugars, and sodium benzoate was minimal in either the batch-mode (log selectivity coefficients <-2.60) or as FIA detector. When the FIA method was used, recoveries averaged 99.70% from mineral water samples spiked with 16.22 and 162.20 ppm quinine. Results for determination of quinine in other drinks such as carbonated (64.88 and 71.37 ppm) and bitter lemon drinks (55.15 ppm) agreed with those of the manufacturer's claimed values of <68, <81, and 51 ppm, respectively. With a sample throughput of 50 samples/h under optimized flow conditions, the method can be routinely used to monitor quinine in such samples.

Bioavailability and preliminary clinical efficacy of intrarectal artesunate in Ghanaian children with moderate malaria

We report the first detailed pharmacokinetic assessment of intrarectal (i.r.) artesunate (ARS) in African children. Artesunate was given intravenously (i.v.; 2.4 mg/kg of body weight) and i.r. (10 or 20 mg/kg formulated as 50- or 200-mg suppositories [Rectocaps]) in a crossover study design to 34 Ghanaian children with moderate falciparum malaria. The median relative bioavailability of dihydroartemisinin (DHA), the active antimalarial metabolite of ARS, was higher in the low-dose i.r. group (10 mg/kg) than in the high-dose i.r. group (20 mg/kg) (58 versus 23%; P = 0.018). There was wide interpatient variation in the area under the concentration-time curve after i.r. ARS administration (up to 9-fold in the high-dose group and 20-fold in the low-dose group). i.r. administered ARS was more rapidly absorbed in the low-dose group than the high-dose group (median [range] absorption half-lives, 0.7 h [0.3 to 1.24 h] versus 1.1 h [0.6 to 2.7 h] [P = 0.023]. i.r. administered ARS was eliminated with a median (range) half-life of 0.8 h (0.4 to 2.7 h) (low-dose group and 0.9 h (0.1 to 2.5 h) (high-dose group) (P = 1). The fractional clearances of DHA were 3.9, 2.6, and 1.5 liters/kg/h for the 20-mg/kg, 10-mg/kg and i.v. groups, respectively (P = 0.001 and P = 0.06 for the high-and low-dose i.r. groups compared with the i.v. groups, respectively). The median volumes of distribution for DHA were 1.5 liters kg (20 mg/kg, i.r. group), 1.8 liters/kg (10 mg/kg, i.r. group), and 0.6 liters/kg (i.v. group) (P < 0.05 for both i.r. groups compared with the i.v. group). Parasite clearance kinetics were comparable in all treatment groups. i.r. administered ARS may be a useful alternative to parenterally administered ARS in the management of moderate childhood malaria and should be studied further.

Pharmacokinetics of artemisinin-type compounds

Various compounds of the artemisinin family are currently used for the treatment of patients with malaria worldwide. They are characterised by a short half-life and feature the most rapidly acting antimalarial drugs to date. They are increasingly being used, often in combination with other drugs, although our knowledge of their main pharmacological features (including their absorption, distribution, metabolism and excretion) is still incomplete. Such data are particularly important in the case of combinations. Artemisinin derivatives are converted primarily, but to different extents, to the bioactive metabolite artenimol after either parenteral or gastrointestinal administration. The rate of conversion is lowest for artelinic acid (designed to protect the molecule against metabolism) and highest for the water-soluble artesunate. The absolute and relative bioavailability of these compounds has been established in animals, but not in humans, with the exception of artesunate. Oral bioavailability in animals ranges, approximately, between 19 and 35%. A first-pass effect is highly probably for all compounds when administered orally. Artemisinin compounds bind selectively to malaria-infected erythrocytes to yet unidentified targets. They also bind modestly to human plasma proteins, ranging from 43% for artenimol to 81.5% for artelinic acid. Their mode of action is still not completely understood, although different theories have been proposed. The lipid-soluble artemether and artemotil are released slowly when administered intramuscularly because of the 'depot' effect related to the oil formulation. Understanding the pharmacokinetic profile of these 2 drugs helps us to explain the characteristics of the toxicity and neurotoxicity. The water-soluble artesunate is rapidly converted to artenimol at rates that vary with the route of administration, but the processes need to be characterised further, including the relative contribution of pH and enzymes in tissues, blood and liver. This paper intends to summarise contemporary knowledge of the pharmacokinetics of this class of compounds and highlight areas that need further research.

Comparative pharmacokinetic study of oral and rectal formulations of artesunic acid in healthy volunteers

OBJECTIVE

A single cross-over, comparative pharmacokinetic study of oral and rectal formulations of 200 mg artesunic acid in 12 healthy Malaysian volunteers is reported.

METHODS

Plasma concentrations of artesunic acid and dihydroartemisinin were determined simultaneously by HPLC with electrochemical detection. The test drug was well tolerated and no undesirable adverse effects were observed.

RESULTS

Comparison of pharmacokinetic parameters of artesunic acid after oral and rectal administration showed statistically significant differences in t(max) and AUC, with no changes for Cmax and t1/2. As for dihydroartemisinin, differences were observed for t(max) and Cmax but not for AUC.

CONCLUSION

There appear to be pharmacokinetic differences between oral and rectal modes of administration. The significance of these findings should be explored in malaria patients before appropriate therapeutic regimens are devised.

Determination of 6,4'-bis-(2-imidazolinylhydrazone)-2-phenylimidazo[1,2-a]py ridine in plasma and whole blood by high-performance liquid chromatography

A selective and sensitive HPLC assay for the quantitative determination of a new antifilarial drug, 6,4'-bis-(2-imidazolinylhydrazone)-2-phenylimidazo[1,2-a]pyr idine (CDR 101) is described. After extraction from plasma and blood, CDR 101 was analysed using a C18 Nucleosil ODS column (250x4.6 mm, 5 microm particle size) and mobile phase of acetonitrile-0.05 M ammonium acetate adjusted to pH 3.0, with UV detection at 318 nm. The mean recoveries of CDR 101 in plasma and blood over a concentration range of 25-500 ng/ml were 95.5+/-2.01% and 83.3+/-1.87%, respectively. The within-day and day-to-day coefficient of variations for plasma were 3.23-6.21% and 2.59-9.90%, respectively, those for blood were 2.59-5.92% and 2.89-6.82%, respectively. The minimum detectable concentration for CDR 101 was 1 ng/ml in plasma and 2.5 ng/ml in whole blood. This method was found to be suitable for clinical pharmacokinetic studies.

Simultaneous determination of artesunic acid and dihydroartemisinin in blood plasma by high-performance liquid chromatography for application in clinical pharmacological studies

A selective reproducible high-performance liquid chromatographic assay for the simultaneous quantitative determination of the antimalarial compound artesunic acid (ARS), dihydroartemisinin (DQHS) and artemisinin (QHS), as internal standard, is described. After extraction from plasma, ARS and DQHS were analysed using an Econosil C8 column and a mobile phase of acetonitrile-0.05 M acetic acid (42:58, v/v) adjusted to pH 5.0 and electrochemical detection in the reductive mode. The mean recovery of ARS and DQHS over a concentration range of 50-200 ng/ml was 75.5% and 93.5%, respectively. The within-day coefficients of variation were 4.2-7.4% for ARS and 2.6-4.9% for DQHS. The day-to-day coefficients of variation were 1.6-9.6% and 0.5-8.3%, respectively. The minimum detectable concentration for ARS and DQHS in plasma was 4.0 ng/ml for both compounds. The method was found to be suitable for use in clinical pharmacological studies.

Single dose pharmacokinetics of oral artemether in healthy Malaysian volunteers

AIMS

To determine the pharmacokinetics of artemether (ARM) and its principal active metabolite, dihydroartemisinin (DHA) in healthy volunteers.

METHODS

Six healthy male Malaysian subjects were given a single oral dose of 200 mg artemether. Blood samples were collected to 72 h. Plasma concentrations of the two compounds were measured simultaneously by reversed-phase h.p.l.c. with electro-chemical detection in the reductive mode.

RESULTS

Mean (+/- s.d.) maximum concentrations of ARM, 310 +/- 153 micrograms l-1, were reached 1.88 +/- 0.21 h after drug intake. The mean elimination half-life was 2.00 +/- 0.59 h, and the mean AUC 671 +/- 271 micrograms l-1 h. The mean Cmax of DHA, 273 +/- 64 micrograms l-1 was observed at 1.92 +/- 0.13 h. The mean AUC of DHA was 753 +/- 233 micrograms h l-1'. ARM and DHA were stable at < or = -20 degrees C for at least 4 months in plasma samples.

CONCLUSIONS

The relatively short half-life of ARM may be one of the factors responsible for the poor radical cure rate of falciparum malaria with regimens employing daily dosing. In view of the rapid loss of DHA in plasma samples held at room temperature (26 degrees C) it is recommended to store them at a temperature of < or = -20 degrees C as early as possible after sample collection.

Determination of a new antimalarial drug, benflumetol, in blood plasma by high-performance liquid chromatography

A rapid and selective high-performance liquid chromatographic assay for determination of a new antimalarial drug (benflumetol, BFL) is described. After extraction with hexane-diethyl ether (70:30, v/v) from plasma, BFL was analysed using a C18 Partisil 10 ODS-3 reversed-phase stainless steel column and a mobile phase of acetonitrile-0.1 M ammonium acetate (90:10, v/v) adjusted to pH 4.9 with ultraviolet detection at 335 nm. The mean recovery of BFL over a concentration range of 50-400 ng/ml was 96.8 +/- 5.2%. The within-day and day-to-day coefficients of variation were 1.8-4.0 and 1.8-4.2%, respectively. The minimum detectable concentration in plasma for BFL was 5 ng/ml with a C.V. of less than 10%. This method was found to be suitable for clinical pharmacokinetic studies.

Plasmodium falciparum: increased proportion of severe resistance (RII and RIII) to chloroquine and high rate of resistance to sulfadoxine-pyrimethamine in Peninsular Malaysia after two decades

Uncomplicated falciparum malaria patients were randomly assigned to receive either 25 mg/kg chloroquine (CHL) over 3 d or a statim dose of 25 mg/kg sulfadoxine (SDX) plus 1.25 mg/kg pyrimethamine (PYR). Patients were followed up for 28 d and the parasite response graded according to World Health Organization criteria. Overall resistance to CHL was 63.3% and 47.4% to SDX/PYR. RI, RII and RIII rates were 9.1%, 42.4% and 12.1% for CHL and 10.5%, 21.1% and 15.8% for SDX/PYR, respectively. Degree and rates of resistance to CHL were significantly correlated with pre-treatment parasite density, but not those to SDX/PYR. Plasma CHL and SDX/PYR levels were within the reported ranges and were not significantly different in patients with sensitive and resistant responses.

Determination of artemether and dihydroartemisinin in blood plasma by high-performance liquid chromatography for application in clinical pharmacological studies

A selective reproducible high-performance liquid chromatographic assay for the simultaneous quantitative determination of the antimalarial compound artemether (ARM), dihydroartemisinin (DQHS) and artemisinin (QHS), as internal standard, is described. After extraction from plasma, ARM and DQHS were analysed using a Lichrocart/Lichrosphere 100 CN stainless-steel column and a mobile phase of acetonitrile-0.05 M acetic acid (15:85, v/v) adjusted to pH 5.0, and electrochemical detection in the reductive mode. The mean recovery of ARM and DQHS over a concentration range of 30-120 ng/ml was 81.6% and 93.4%, respectively. The within-day coefficients of variation were 0.89-7.01% for ARM and 3.45-8.11% for DQHS. The day-to-day coefficients of variation were 2.06-8.43% and 3.22-6.33%, respectively. The minimum detectable concentration for ARM and DQHS in plasma was 2.5 and 1.25 ng/ml for both compounds. The method was found to be suitable for use in clinical pharmacological studies.

Determination of the antifilarial drug UMF-078 and its metabolites UMF-060 and flubendazole in whole blood using high-performance liquid chromatography

A rapid and selective high-performance liquid chromatographic (HPLC) method for the simultaneous determination of the antifilarial drug UMF-078 (I) and its metabolites UMF-060 (II) and flubendazole (III) is described. After a simple extraction from whole blood, the compounds were determined by HPLC using a C18 Inertsil ODS-2 reversed-phase column with methanol-0.05M ammonium acetate (pH 4.0) as the mobile phase and ultraviolet detection at 291 nm. The average recoveries of I, II and III over the concentration range 20-500 ng ml-1 were 69.9 +/- 4.7, 85.6 +/- 4.4 and 85.1 +/- 6.0%, respectively. The minimum detectable concentrations in whole blood for I, II and III were 10, 7 and 7 ng ml-1, respectively. This method was found to be suitable for pharmacokinetic studies.

Determination of naltrexone dosage for narcotic agonist blockade in detoxified Asian addicts

Thirty-eight, adult, male, detoxified, Malaysian opiate addicts participated in this double-blind clinical evaluation of naltrexone. Addicts from three ethnic groups: Chinese, Malays, and Indians received a weekly regimen of naltrexone (100 mg on Days 1 and 3, and 150 mg on Day 5). Subjects were randomly assigned to receive intravenous challenge with either 25 mg heroin or placebo 12, 24, 48, and 72 h after the third naltrexone dose. Physiological and subjective parameters were measured at each challenge interval. Results indicated that naltrexone was effective in blocking the physiological and psychological effects of heroin for at least 48 and 72 h, respectively, in detoxified Malaysian opiate addicts. The efficacy of naltrexone did not differ among the three ethnic groups evaluated in this study.

Determination of a new antifilarial drug, UMF-058, and mebendazole in whole blood by high-performance liquid chromatography

A rapid and selective high-performance liquid chromatographic assay for simultaneous quantitative determination of a new antifilarial drug (UMF-058, I) and mebendazole (MBZ) is described. After a simple extraction from whole blood, both compounds were analysed using a C18 Nova Pak reversed-phase column and a mobile phase of methanol-0.05 M ammonium dihydrogenphosphate (50:50, v/v) adjusted to pH 4.0, with ultraviolet detection at 291 nm. The average recoveries of I and MBZ over a concentration range of 25-250 ng/ml were 92.0 +/- 7.7 and 84.4 +/- 4.4%, respectively. The minimum detectable concentrations in whole blood for I and MBZ were 7 and 6 ng/ml, respectively. This method was found to be suitable for pharmacokinetic studies.

Treatment of subperiodic Brugia malayi infection with a single dose of ivermectin

A clinical trial on the efficacy of a single oral dose of ivermectin at 20, 50, 100, and 200 micrograms/kg was carried out in 40 subjects with subperiodic Brugia malayi microfilaremia. There was no significant difference in the clearance of microfilaremia in the four treatment groups, and the lowest geometric mean microfilarial count (GMC) achieved in the 40 subjects was 8.8/ml or 8.3% of the initial count (106.1/ml), at two weeks post-treatment. The GMC started to increase at one month post-treatment and by six months was 22.2% of the initial GMC. Only 27.5%, 23.1%, 15.0%, and 18.9% of subjects were amicrofilaremic at two, four, 12, and 24 weeks post-treatment, respectively. Mild fever in 35% of the subjects was the primary side reaction and was more common in those with microfilarial counts > or = 500/ml (85.7%) than in those with counts < 500/ml (32%). The clearance of B. malayi microfilaremia by ivermectin was less rapid than that reported for Wuchereria bancrofti. The smaller number of side reactions encountered in the present study compared with those reported for bancroftian filariasis is probably related to the lower microfilarial density in the present subjects. Since ivermectin at a single oral dose of 20-200 micrograms/kg can reduce the GMC to less than 10% at two weeks and maintain it below 25% of the initial level even at six months post-treatment, it is recommended that the drug be seriously evaluated for use in the control of brugian filariasis.

The effect of fever on quinine and quinidine disposition in the rat

The pharmacokinetics of quinine and its diastereoisomer quinidine has been investigated in normal and febrile rats. Endotoxin-induced fever in rats resulted in an increased quinine clearance (CL) (4.49 +/- 1.45 vs 1.38 +/- 0.65 L h-1 kg-1, P less than 0.001) and volume of distribution (Vd) (42.6 +/- 8.8 vs 28.9 +/- 10.3 L kg-1, P less than 0.05) with a concomitant shortening of the elimination half-life (t1/2) (7.1 +/- 2.5 vs 15.9 +/- 5.9 h, P less than 0.01). With quinidine, however, fever resulted in an increased CL (3.95 +/- 1.05 vs 1.89 +/- 0.60 L h-1 kg-1, P less than 0.002) with no change in Vd and a significant decrease in t1/2 (5.1 +/- 0.7 vs 10.1 +/- 2.8 h, P less than 0.001). In both studies there was no significant difference in hepatic microsomal protein or cytochrome P450 content. Neither drug accumulated in the liver but low concentrations of quinidine were present in the heart 24 h after administration. In-vitro studies suggest that temperature does not alter the binding of either drug. These data suggest that fever enhances the clearance of quinine and quinidine. These findings may offer some additional explanation of the lack of serious quinine and quinidine toxicity during the treatment of malaria infection, even after large dosages of the drug administered during the initial period of treatment when fever is most intense.

The influence of alpha 1-acid glycoprotein on quinine and quinidine disposition in the rat isolated perfused liver preparation

We have studied the effect of 0.5 and 2.0 g L-1 of alpha 1-acid glycoprotein (AAG) on the disposition of quinine and quinidine in the rat isolated perfused liver preparation. The higher concentration of AAG (2.0 g L-1) resulted in a significant decrease in clearance [quinine study (control: 9.6 +/- 2.9 vs test: 3.1 +/- 1.2 mL min-1); quinidine study (control: 9.8 +/- 2.4 vs test: 3.5 +/- 1.1 mL min-1]) and volume of distribution [quinine study (control: 1198 +/- 416 vs test: 466 +/- 95 mL); quinidine study (control: 1352 +/- 459 vs test: 317 +/- 24 mL]) but not the elimination half-life compared with control. At the lower concentration (0.5 g L-1) of AAG there was no significant difference in clearance, volume of distribution and elimination half-life for either drug compared with control. By increasing the concentration of AAG from 0.5 to 2.0 g L-1 both the hepatic extraction ratio and the fraction of drug unbound when compared with controls significantly decreased by about 66 and 60% for quinine, and by 65 and 58% for its diastereoisomer quinidine, respectively. The consequence of these changes is a substantial increase in the total quinine (or quinidine) concentrations without any change in the free quinine (or quinidine) concentrations. However, at 0.5 g L-1 AAG compared with control, no significant difference was observed in fraction of drug unbound, extraction ratio, total drug concentration or free drug concentration for either drug. In summary, changing concentrations of AAG, an important binding protein for quinine and quinidine, can affect the hepatic disposition of both drugs.

Effect of Plasmodium falciparum malaria infection on the plasma concentration of alpha 1-acid glycoprotein and the binding of quinine in Malawian children

1. We have measured plasma concentrations of alpha 1-acid glycoprotein (AGP) in 18 healthy children and 85 children with falciparum malaria in Malawi. In addition, we determined the degree of protein binding of quinine (QN) in the plasma of 52 of the patients and each of the healthy controls. 2. The mean plasma AGP concentration was higher in patients than in controls (P less than 0.0001) and remained elevated 3 weeks after complete resolution of malaria infection. 3. The mean unbound QN fraction was significantly less (P less than 0.00001) in patients with malaria (0.128 +/- 0.037) than in controls (0.193 +/- 0.051) and significantly higher (P = 0.02) in convalescence (0.153 +/- 0.067) than during acute illness. 4. There were highly significant negative correlations between plasma AGP concentration and the free QN fraction in spiked plasma samples (r = -0.534, P less than 0.0001, n = 93) and in clinical samples (r = -0.484, P less than 0.00001, n = 225). There was a significant positive correlation between plasma concentrations of AGP and another acute phase reactant, C reactive protein (P less than 0.001).

The effect of malaria infection on paracetamol disposition in the rat

The effect of Plasmodium berghei infection, a rodent malarial model, on the disposition of paracetamol (50 mg/kg, i.v.) was investigated in rats. Malaria infection (MI) resulted in a significant decrease in clearance (control: 21.6 +/- 5.5 vs test: 11.8 +/- 2.9 mL/min/kg, P less than 0.005) with no change in volume of distribution and a significant prolongation of the elimination half-life (control: 30.7 +/- 6.3 vs 53.3 +/- 12.1 min, P less than 0.005) of paracetamol in malaria infected rats. These changes were not related to the severity of MI. Malaria infection also decreased biliary clearance of paracetamol (64%) but not its glucuronide and sulphate conjugates in the bile compared with controls. In addition, glutathione conjugates were not detected in bile samples of malaria infected rats. These data suggest that important pathways of drug detoxification may be compromised by MI in a relatively selective fashion and the relevance of these findings to the clinical use of drugs eliminated by these pathways merits further study.

The effect of malaria infection on antipyrine metabolite formation in the rat

We have shown that malaria infection can impair selectively the formation of antipyrine metabolites in the rat. During malaria, a significant increased urinary levels of unchanged antipyrine was observed (control: 1.7 +/- 0.4 vs test: 8.1 +/- 1.1% of dose, P less than 0.001). This was associated with significantly decreased excretion of 3-hydroxymethylantipyrine (control: 24.5 +/- 1.2 vs test: 21.4 +/- 0.7%, P less than 0.001) and 4-hydroxyantipyrine (control: 20.1 +/- 0.9 vs test: 15.5 +/- 1.3%, P less than 0.001) but not norantipyrine compared to control. Following treatment of the malaria infection with halofantrine, only the formation of 3-hydroxymethylantipyrine (control: 25.2 +/- 0.9 vs test: 24.1 +/- 0.6%, P less than 0.05) is impaired. The implications of these findings in relation to metabolism of other antimalarial drugs during malaria remains to be elucidated. Further work is needed to determine the changes in the pharmacokinetics of AP and its metabolites before, during and after MI in the rat in order to give a better insight into the effect of MI on hepatic drug metabolism.

The safety and kinetics of intramuscular quinine in Malawian children with moderately severe falciparum malaria

The safety and kinetics of intramuscular quinine (10 mg salt/kg every 8 h for 3 doses) were assessed in Malawian children suffering from uncomplicated falciparum malaria, who were unable to take oral antimalarial drugs. Treatment was completed with oral pyrimethamine-sulfadoxine. The mean (+/- SD) peak plasma quinine concentration after the first injection was 9.0 (+/- 2.3) micrograms/ml, at 1.1 (+/- 0.7) h. Mean plasma concentrations increased further after the second and third doses to a maximum of 11.5 (+/- 2.6) micrograms/ml at 16.1 (+/- 3.2) h. No hypotension, hypoglycaemia or electrocardiographic abnormalities developed during quinine treatment. These results provide further evidence for the safety of intramuscular quinine in children with moderately severe malaria. Plasma concentrations of alpha 1-acid glycoprotein (AGP) were higher, and the degree of protein binding of quinine was greater, in acute malaria than in convalescence. There was a significant correlation between AGP concentration and the fraction of plasma quinine bound to plasma protein. These findings suggest a role for AGP in the binding of quinine in plasma in vivo and are of interest since unbound quinine is responsible for both the efficacy and toxicity of the drug.

The effect of malaria infection on the disposition of quinine and quinidine in the rat isolated perfused liver preparation

The effect of malaria on the disposition of quinine and quinidine was studied in livers isolated from young rats infected with merozoites of Plasmodium berghei, a rodent malaria model, and non-infected controls. Following bolus administration of quinine (1 mg) or quinidine (1 mg) to the 100 mL recycling perfusion circuit, perfusate was sampled (0-4 h) and plasma assayed for quinine and quinidine by HPLC. Higher quinine (AUC:6470 +/- 1101 vs 3822 +/- 347 ng h mL-1, P less than 0.001) and quinidine (AUC: 6642 +/- 1304 vs 4808 +/- 872 ng h mL-1, P less than 0.05) concentrations were observed during malaria infection (MI). MI resulted in decreased quinine clearance (CL) (0.33 +/- 0.08 vs 0.64 +/- 0.09 mL min-1 g-1, P less than 0.001) and volume of distribution (Vd) (53.0 +/- 13.3 vs 81.2 +/- 23.7 mL g-1, P less than 0.05) but no significant change in elimination half-life (t1/2) (1.93 +/- 0.6 vs 1.37 +/- 0.25 h, P greater than 0.05). With quinidine, however, MI resulted in decreased CL (0.38 +/- 0.16 vs 0.64 +/- 0.09, P less than 0.05) with no change in Vd and a significant increase in t1/2 (1.62 +/- 0.42 vs 0.88 +/- 0.22, P less than 0.01). In summary, the hepatic disposition of quinine and quinidine is altered in the malaria-infected rat.

Single dose kinetic study of the triple combination mefloquine/sulphadoxine/pyrimethamine (Fansimef) in healthy male volunteers

A single dose pharmacokinetic study of a combined antimalarial formulation of mefloquine, sulphadoxine and pyrimethamine (Fansimef) has been performed in 10 healthy adult male Malaysian volunteers. The dose consisted of two tablets containing 250 mg mefloquine base, 500 mg sulphadoxine base and 25 mg pyrimethamine base each. Plasma concentrations of mefloquine and pyrimethamine were measured by GC-ECD, those of sulphadoxine by h.p.l.c. Time to peak concentrations (mean +/- s.d. for mefloquine (5.70 +/- 0.95 h), sulphadoxine (3.75 +/- 2.03 h) and pyrimethamine (3.30 +/- 1.98 h) were similar to those observed by others after administration of the single compounds. This was also true for elimination half-lives (t1/2). The t1/2s for mefloquine, sulphadoxine and pyrimethamine were 387 +/- 98 h, 255 +/- 61 h and 114 +/- 42 h, respectively.