Design, synthesis and evaluation of new 4-arylthiazole-2-amine derivatives as acetylcholinesterase inhibitors.

A series of new 4-arylthiazole-2-amine derivatives as acetylcholinesterase inhibitors (AChEIs) were designed and synthesized, Furthermore, their inhibitory activities against acetylcholinesterase in vitro were tested by Ellman spectrophotometry, and the results of inhibitory activity test showed that most of them had a certain acetylcholinesterase inhibitory activity in vitro. Moreover, the IC50 value of compound 4f was to 0.66 µM, which was higher than that of Rivastigmine and Huperzine-A as reference compounds, and it had a weak inhibitory effect on butyrylcholinesterase. The potential binding mode of compound 4f with AChE was investigated by the molecular docking, and the results showed that 4f was strongly bound up with AChE with the optimal conformation, in addition, their binding energy reached -11.27 Kcal*mol-1. At last, in silico molecular property of the synthesized compounds were predicted by using Molinspiration online servers. It can be concluded that the lead AChEIs compound 4f presented satisfactory drug-like characteristics.

Determination of five sesquiterpenoids in Xingnaojing injection by quantitative analysis of multiple components with a single marker.

A quantitative analysis of multiple components with a single-marker method was established for the simultaneous determination of five sesqutiterpenoids in Xingnaojing injection. This method was established with Xingnaojing injection determined by high-performance liquid chromatography coupled with diode array detection. The durability and system suitability of the established method were evaluated, and the reliable relative correction factors were obtained with curdione selected as an internal reference. The contents of the five components in all Xingnaojing injections were determined by external standard method and the contents of curcumenone, curcumenol, curzerenone, and germacrone were also calculated with the obtained relative correction factors. Then, relative error was investigated to estimate the difference of the two methods. As a result, the established new method possesses good adaptability, and there is no significant difference between the two methods, except for the content of curzerenone in eight samples. To put the established method into practice, the limits of quantitation of the established method of the five components were proposed and defined. Thus, the developed methodology can also be utilized to the quality evaluation of Xingnaojing injection, in spite of the difference found in the content of curzerenone between the external standard method and the newly established method.

A new facile synthesis of d4-pterosin B and d4-bromopterosin, deuterated analogues of ptaquiloside.

Ptaquiloside (Pta) is a potent carcinogen present in bracken fern and in soil matrices, that can potentially leach to the aquatic environment. More recently its presence in the milk of different farm animals has been reported. Pterosin B (Ptb) and bromopterosin (BrPt) represent the most convenient analogues in the detection of ptaquiloside by mass spectrometry. Pterosin sesquiterpenes are also involved in many patented biomedical protocols. In this work we introduce a new and convenient approach to the synthesis in three steps and more than 80% yield of d4-pterosin B (d4-Ptb) and d4-bromopterosin (d4-BrPt), useful as internal standards in the quantification of ptaquiloside.

Direct quantitation of active ingredients in solid artesunate antimalarials by noncovalent complex forming reactive desorption electrospray ionization mass spectrometry.

The direct quantitation of active ingredients in solid pharmaceutical tablets by desorption electrospray ionization mass spectrometry (DESI MS) is complicated by the dependence of the DESI signal on variables such as spray angles and distances, morphological sample properties, and the difficulty of properly incorporating an internal standard. Here, a DESI MS method for the direct quantitative screening of widely counterfeited antimalarial tablets containing artesunate is presented. This method is based on reactive DESI, where analyte desorption and ionization occur by the formation of noncovalent complexes between alkylamine molecules in the DESI spray solution and artesunate molecules exposed on the sample surface in the open air. For quantitation purposes, the internal standard d4-artesunic acid was synthesized by esterification of d4-succinic anhydride and dihydroartemisinin, and homogeneously dispersed on the tablet surface via a controlled deposition procedure. The analyte-to-internal standard signal intensity ratio was observed to be largely independent of all DESI variables, only showing dependence on tablet hardness. Analysis of artesunate tablet standards prepared with known amounts of the active ingredient in the 0.02 to 0.32 mg artesunate mg(-1) tablet range resulted in a calibration curve with good linearity (r = 0.9985). Application of this method to the direct quantitation of genuine artesunate tablets from Vietnam showed a 6% (n = 4) precision and 94% accuracy after the spectral data were corrected for tablet hardness.

Antimalarial drug quality in Africa.

BACKGROUND AND OBJECTIVE: There are several reports of sub-standard and counterfeit antimalarial drugs circulating in the markets of developing countries; we aimed to review the literature for the African continent. METHODS: A search was conducted in PubMed in English using the medical subject headings (MeSH) terms: 'Antimalarials/analysis'[MeSH] OR 'Antimalarials/standards'[MeSH] AND 'Africa'[MeSH]' to include articles published up to and including 26 February 2007. Data were augmented with reports on the quality of antimalarial drugs in Africa obtained from colleagues in the World Health Organization. We summarized the data under the following themes: content and dissolution; relative bioavailability of antimalarial products; antimalarial stability and shelf life; general tests on pharmaceutical dosage forms; and the presence of degradation or unidentifiable impurities in formulations. RESULTS AND DISCUSSION: The search yielded 21 relevant peer-reviewed articles and three reports on the quality of antimalarial drugs in Africa. The literature was varied in the quality and breadth of data presented, with most bioavailability studies poorly designed and executed. The review highlights the common finding in drug quality studies that (i) most antimalarial products pass the basic tests for pharmaceutical dosage forms, such as the uniformity of weight for tablets, (ii) most antimalarial drugs pass the content test and (iii) in vitro product dissolution is the main problem area where most drugs fail to meet required pharmacopoeial specifications, especially with regard to sulfadoxine-pyrimethamine products. In addition, there are worryingly high quality failure rates for artemisinin monotherapies such as dihydroartemisinin (DHA); for instance all five DHA sampled products in one study in Nairobi, Kenya, were reported to have failed the requisite tests. CONCLUSIONS: There is an urgent need to strengthen pharmaceutical management systems such as post-marketing surveillance and the broader health systems in Africa to ensure populations in the continent have access to antimalarial drugs that are safe, of the highest quality standards and that retain their integrity throughout the distribution chain through adequate enforcement of existing legislation and enactment of new ones if necessary, and provision of the necessary resources for drug quality assurance.

Determination of atractylenolide II in rat plasma by reversed-phase high-performance liquid chromatography.

A method for quantitative determination of atractylenolide II in rat plasma using reversed-phase high-performance liquid chromatography (RP-HPLC) coupled with UV spectrometry was established. From a variety of compounds and solvents tested, atractylenolide III was selected as the internal standard (IS) and ethyl acetate was found to be the best solvent for extracting atractylenolide II from plasma samples. RP-HPLC analysis of the extracts was performed on an analytical column (DIKMA ODS, 150 x 4.6 mm; i.d., 5 microm) equipped with a security guard pre-column system. There was good linearity over the range 0.05-5.0 microg/mL (r > 0.99). The recoveries were more than 90.0% in plasma, and the intra- and inter-day coefficients of variation were less than 10.0% in all cases. The limit of detection (LOD) was 0.025 microg/mL and the lower limit of quantification (LLOQ) was 0.05 microg/mL. The RP-HPLC method was applied to quantitate atractylenolide II in rat plasma within 24 h in a pharmacokinetics study where experimental rats received a single dose of atractylenolide II (60 mg/kg).

Fake antimalarials in Southeast Asia are a major impediment to malaria control: multinational cross-sectional survey on the prevalence of fake antimalarials.

OBJECTIVE: To assess the prevalence of counterfeit antimalarial drugs in Southeast (SE) Asia. DESIGN: Cross-sectional survey. SETTING: Pharmacies and shops selling antimalarial drugs in Myanmar (Burma), Lao PDR, Vietnam, Cambodia and Thailand. MAIN OUTCOME MEASURES: Proportion of artemisinin derivatives or mefloquine containing drugs of substandard quality. RESULTS: Of the 188 tablet packs purchased which were labelled as 'artesunate' 53% did not contain any artesunate. All counterfeit artesunate tablets were labelled as manufactured by 'Guilin Pharma', and refinements of the fake blisterpacks made them often hard to distinguish from their genuine counterparts. No other artemisinin derivatives were found to be counterfeited. Of the 44 mefloquine samples, 9% contained <10% of the expected amount of active ingredient. CONCLUSIONS: An alarmingly high proportion of antimalarial drugs bought in pharmacies and shops in mainland SE Asia are counterfeit, and the problem has increased significantly compared with our previous survey in 1999-2000. This is a serious threat to public health in the region.

Stability control of valerian ground material and extracts: a new HPLC-method for the routine quantification of valerenic acids and lignans.

A new HPLC-method for the separation of medium polar and nonpolar compounds in preparations of Valeriana officinalis was established for stability control. Powdered valerian root and a commercial ethanolic valerian extract were investigated for apparent differences in stability behaviour. Storage conditions were chosen according to the ICH-guidelines. Changes in composition of valerenic acids and lignans were observed depending on storage conditions and packaging materials. Hydroxyvalerenic acid, pinoresinol and hydroxypinoresinol were identified as degradation products in Valerian root, especially during accelerated testing. Ethanolic extracts appeared not to be as sensitive for chemical degradation under climatic influences compared to the crude plant material, and showed no increase in the amounts of lignan-aglyka. In comparison, extracts showed high sensitivity on changes of physical properties like loss on drying and viscosity.

Design of a dissolution system for the evaluation of the release rate characteristics of artemether and dihydroartemisinin from tablets.

As none of the pharmacopoeial dissolution methods are suitable to evaluate the release rate of artemether and dihydroartemisinin from tablets, a 'two-phase partition-dissolution' method, based on the one of [J. Pharm. Sci. 85 (1996) 1060] was developed. It consists of an organic solvent in the upper part and the aqueous phase, in which the dissolution test was executed. The main requirements for the selection of the solvent are: the density should be lower than 1; the analyte should dissolve in the organic part as much as required for 'sink' conditions; if possible, the cut off should be near 200 nm, which allows direct HPLC measurement at 215 nm. The most suitable solvent for artemether is isooctane in a ratio of 100/150 ml aqueous phase. Samples could be analysed without further treatment. For dihydroartemisinin, chlorobutane was selected in a ratio 150/150 ml water. In the latter method, the solvent disturbed in the HPLC analysis and therefore samples were evaporated and then reconstituted in methanol. Repeatability of the test was satisfactory and discrimination ability tests on Artenam tablet batches and self-made dihydroartemisinin tablets, respectively, showed good results, confirmed via calculation of the similarity factor f2 (value <50). Dissolution determination of Cotecxin tablets was proven not to be conform as immediate-release tablet.

Authentication of artemether, artesunate and dihydroartemisinin antimalarial tablets using a simple colorimetric method.

The recent and widespread appearance of counterfeit antimalarial tablets in South-east Asia prompted the search for simple field assays to identify genuine drugs. In a recently described colorimetric assay for artesunate, Fast red TR salt reacted with an alkali-decomposition product of artesunate to produce a distinct yellow colour. However, that assay is specific for artesunate and it cannot be used to test for artemether. Because of potential concerns over artemether tablet counterfeiting, the colorimetric assay was modified to detect artemether, dihydroartemisinin and artesunate tablets. Other common antimalarials (artemisinin, chloroquine diphosphate, mefloquine HCl, sulphadoxine and pyrimethamine), as well as aspirin and acetaminophen, were negative in the assay, indicating its specificity for artemether, dihydroartemisinin and artesunate. The colorimetric method can be used to obtain a rapid visual assessment of tablet authenticity. The method can also be used to quantify the drug content of tablets, when used in conjunction with a spectrophotometer.

Fake artesunate in southeast Asia.

Artesunate is a key antimalarial drug in the treatment of multidrug-resistant Plasmodium falciparum malaria in southeast Asia. We investigated the distribution of counterfeit artesunate tablets by use of the validated, simple, and inexpensive Fast Red TR dye technique. We also aimed to identify distinguishing characteristics of the fake drugs. Of 104 shop-bought "artesunate" samples from Cambodia, Laos, Myanmar (Burma), Thailand, and Vietnam, 38% did not contain artesunate. Characteristics such as cost and physical appearance of the tablets and packaging reliably predicted authenticity. The illicit trade in counterfeit antimalarials is a great threat to the lives of patients with malaria. The dye test will assist national malaria control authorities in urgently needed campaigns to stop this murderous trade.

Efficacy of six doses of artemether-lumefantrine (benflumetol) in multidrug-resistant Plasmodium falciparum malaria.

The new oral fixed combination artemether-lumefantrine (CGP 56697) has proved to be an effective and well-tolerated treatment of multi-drug resistant Plasmodium falciparum malaria, although cure rates using the four-dose regimen have been lower than with the currently recommended alternative of artesunate-mefloquine. Two six-dose schedules (total adult dose = 480 mg of artemether and 2,880 mg of lumefantrine) were therefore compared with the previously used four-dose regimen (320 mg of artemether and 1,920 mg of lumefantrine) in a double-blind trial involving 359 patients with uncomplicated multidrug-resistant falciparum malaria. There were no differences between the three treatment groups in parasite and fever clearance times, and reported adverse effects. The two six-dose regimens gave adjusted 28-day cure rates of 96.9% and 99.12%, respectively, compared with 83.3% for the four-dose regimen (P < 0.001). These six-dose regimens of artemether-lumefantrine provide a highly effective and very well-tolerated treatment for multidrug-resistant falciparum malaria.