Extraction-assisted voltammetric determination of homocysteine using magnetic nanoparticles modified with molecularly imprinted polymer.

A magnetic graphite-epoxy composite (m-GEC) electrochemical sensor is presented based on magnetic imprinted polymer (mag-MIP) to determine homocysteine (Hcy). Mag-MIP was synthesized via precipitation polymerization, using functionalized magnetic nanoparticles (Fe3O4) together with the template molecule (Hcy), the functional monomer 2-hydroxyethyl methacrylate (HEMA), and the structural monomer trimethylolpropane trimethacrylate (TRIM). For mag-NIP (magnetic non-imprinted polymer), the procedure was the same in the absence of Hcy. Morphological and structural properties of the resultant mag-MIP and mag-NIP were examined using TEM, FT-IR, and Vibrating Sample Magnetometer. Under optimized conditions, the m-GEC/mag-MIP sensor showed a linear range of 0.1-2 µmol L-1, with a limit of detection (LOD) of 0.030 µmol L-1. In addition, the proposed sensor responded selectively to Hcy compared to several interferents present in biological samples. The recovery values determined by differential pulse voltammetry (DPV) were close to 100% for natural and synthetic samples, indicating good method accuracy. The developed electrochemical sensor proves to be a suitable device for determining Hcy, with advantages related to magnetic separation and electrochemical analysis.

Antibacterial activity of the alkaloid-enriched extract from Prosopis juliflora pods and its influence on in vitro ruminal digestion.

The purpose of this study was to assess the in vitro antimicrobial activity of alkaloid-enriched extracts from Prosopis juliflora (Fabaceae) pods in order to evaluate them as feed additives for ruminants. As only the basic chloroformic extract (BCE), whose main constituents were juliprosopine (juliflorine), prosoflorine and juliprosine, showed Gram-positive antibacterial activity against Micrococcus luteus (MIC = 25 µg/mL), Staphylococcus aureus (MIC = 50 µg/mL) and Streptococcus mutans (MIC = 50 µg/mL), its influence on ruminal digestion was evaluated using a semi-automated in vitro gas production technique, with monensin as the positive control. Results showed that BCE has decreased gas production as efficiently as monensin after 36 h of fermentation, revealing its positive influence on gas production during ruminal digestion. Since P. juliflora is a very affordable plant, this study points out this alkaloid enriched extract from the pods of Prosopis juliflora as a potential feed additive to decrease gas production during ruminal digestion.

Insecticide resistance in Aedes aegypti populations from Ceará, Brazil.

BACKGROUND: Organophosphates and pyrethroids are used widely in Brazil to control Aedes aegypti, the main vector of dengue viruses, under the auspices of the National Programme for Dengue Control. Resistance to these insecticides is widespread throughout Brazil. In Ceará the vector is present in 98% of districts and resistance to temephos has been reported previously. Here we measure resistance to temephos and the pyrethroid cypermethrin in three populations from Ceará and use biochemical and molecular assays to characterise resistance mechanisms. RESULTS: Resistance to temephos varied widely across the three studied populations, with resistance ratios (RR(95)) of 7.2, 30 and 192.7 in Juazeiro do Norte, Barbalha and Crato respectively. The high levels of resistance detected in Barbalha and Crato (RR(95) ≥ 30) imply a reduction of temephos efficacy, and indeed in simulated field tests reduced effectiveness was observed for the Barbalha population. Two populations (Crato and Barbalha) were also resistant to cypermethrin, whilst Juazeiro do Norte showed only an altered susceptibility. The Ile1011Met kdr mutation was detected in all three populations and Val1016Ile in Crato and Juazeiro do Norte. 1011Met was significantly associated with resistance to cypermethrin in the Crato population. Biochemical tests showed that only the activity of esterases and GSTs, among the tested detoxification enzymes, was altered in these populations when compared with the Rockefeller strain. CONCLUSIONS: Our results demonstrate that two A. aegypti populations from Ceará are under strong selection pressure by temephos, compromising the field effectiveness of this organophosphate. Our results also provide evidence that the process of reducing resistance to this larvicide in the field is difficult and slow and may require more than seven years for reversal. In addition, we show resistance to cypermethrin in two of the three populations studied, and for the first time the presence of the allele 1016Ile in mosquito populations from northeastern Brazil. A significant association between 1011Met and resistance was observed in one of the populations. Target-site mechanisms seem not to be implicated in temephos resistance, reinforcing the idea that for the studied populations, detoxification enzymes most likely play a major role in the resistance to this insecticide.

Activities of naphthoquinones against Aedes aegypti (Linnaeus, 1762) (Diptera: Culicidae), vector of dengue and Biomphalaria glabrata (Say, 1818), intermediate host of Schistosoma mansoni.

Larvicidal (against Aedes aegypti Linnaeus, 1762) and molluscicidal (against Biomphalaria glabrata Say, 1818) activities of several natural and synthetic naphthoquinones were measured, with significant results. The best larvicidal compound is 3-bromojuglone, while the better molluscicides are 2-bromo- and 3-bromo-5-acetoxy-1,4-naphthoquinones together with the 3-bromo-5-methoxy derivative. The present results reinforce the potential use of substituted hydroxyquinones, their salts and halogenated quinones as very promising compounds against 4th instar larves of Aedes aegypti, the vector of dengue and against adult snail of Biomphalaria glabrata.

Antileishmanial activity of lapachol analogues

The antileishmanial activity of lapachol, isolapachol, and dihydrolapachol, along with soluble derivatives (potassium salt) and acetate was obtained. All the compounds were assayed against metacyclic promastigotes of two different species of Leishmania associated to tegumentar leishmaniasis: L. amazonensis and L. braziliensis. All compounds presented significant activity, being isolapachol acetate the most active against promastigotes, with IC50/24h = 1.6 ± 0.0 µg/ml and 3.4 ± 0.5 µg/ml for, respectively, L. amazonensis and L. braziliensis. This compound was also assayed in vivo against L. amazonensis and showed to be active. Its toxicity in vitro was also established, and at concentration similar to the IC50, no toxicity was evidenced. In all experiments, pentamidine isethionate was used as a reference drug. The present results reinforce the potential use of substituted hydroxyquinones and derivatives as promising antileishmanial drugs and suggest a continuing study within this class of compounds.

Antileishmanial activity of lapachol analogues.

The antileishmanial activity of lapachol, isolapachol, and dihydrolapachol, along with soluble derivatives (potassium salt) and acetate was obtained. All the compounds were assayed against metacyclic promastigotes of two different species of Leishmania associated to tegumentar leishmaniasis: L. amazonensis and L. braziliensis. All compounds presented significant activity, being isolapachol acetate the most active against promastigotes, with IC50/24h = 1.6 +/- 0.0 microg/ml and 3.4 +/- 0.5 microg/ml for, respectively, L. amazonensis and L. braziliensis. This compound was also assayed in vivo against L. amazonensis and showed to be active. Its toxicity in vitro was also established, and at concentration similar to the IC50, no toxicity was evidenced. In all experiments, pentamidine isethionate was used as a reference drug. The present results reinforce the potential use of substituted hydroxyquinones and derivatives as promising antileishmanial drugs and suggest a continuing study within this class of compounds.