Anticholinesterasic, nematostatic and anthelmintic activities of pyridinic and pyrazinic compounds.

In the search for acetylcholinesterase inhibitors as a potential target for the discovery of anthelmintic drugs, a series of 27 pyridinic and pyrazinic compounds have been designed on the basis of molecular hybridization of two known AChE inhibitors, namely, tacrine and (-)-3-O-acetylspectaline, and on the concept of isosterism. The synthesized compounds generally presented moderate anticholinesterasic activities when compared with the positive control physostigmine, but one compound (ethyl 2-[(6-chloropyrazin-2-yl)sulfanyl] acetate) exhibited an in vitro ability to immobilize the root-knot nematode Meloidogyne incognita that was highly comparable to that of the positive control Temik. Moreover, in anthelmintic assays against the gastrointestinal parasitic nematode Nippostrongylus brasiliensis (L4), some of the compounds, such as (6-chloropyrazin-2-yl)sulfanyl ethanol (32, EC50 = 33 nM), presented activities that were considerably stronger than that of the positive control albendazole (EC50 = 340 nM). In the light of the positive results obtained in the anthelmintic evaluations, the acute oral toxicity of the representative compound diethyl 2,2'-[(3-nitropyridine-2,6-diyl) bissulfanediyl] diacetate was determined in rats, and the drug was shown to be non-toxic at a dose of 2000 mg/kg. These results, allied with the relatively simple structures of the active compounds and their facile synthesis, highlight their potential use as anthelmintic or nematicidic agents.

Comparison of extraction solvents and conditions for herbicide residues in milled rice with liquid chromatography-diode array detection analysis (LC-DAD).

Different extraction procedures and clean-up methods were compared in order to develop a sample preparation procedure for the multi-residue analysis of six post-emergence herbicides (metsulfuron methyl, bensulfuron methyl, pyrazosulfuron ethyl, bentazone, bispyribac sodium and cyhalofop butyl) in rice grains followed by liquid chromatography-diode array detection (LC-DAD). Optimum results were obtained dispersing milled rice grain in water, followed by the addition of 1% acetic acid in acetonitrile, MgSO(4) and sodium acetate as a modification of the quick, easy, cheap, effective, rugged and safe (QuEChERS) method but no primary and secondary amine (PSA) sorbent was added due to the acidic nature of the herbicides. The method was further expanded to other post-emergence herbicides (quinclorac, clomazone and propanil). Except for quinclorac, which cannot be analysed with this method, the recoveries of the other eight herbicides were in the range 73-111%, with relative standard deviations lower than 12%. Limits of detection (LODs) ranged from 0.03 to 0.08 mg kg(-1). A single analyst can extract twelve samples in 4 h. The method presented here allows the simultaneous residue determination of the most common post-emergence herbicides employed in cultivating rice. It is simple, rapid, sensitive, and can be applied routinely to polished rice grain herbicide residue analysis.

Use of palmae wax hydrocarbon fractions as chemotaxonomical markers in Butia and Syagrus.

The wax hydrocarbon fractions of native Butia and Syagrus species collected from Palms in different regions of the of Rio Grande do Sul state (Brazil) and in Rocha (Uruguay) were analyzed to evaluate their potential as chemotaxonomic markers. The wax was extracted with chloroform and the resulting wax was fractionated by preparative TLC. The hydrocarbon fractions were analyzed by GC-MS. Statistical analyses were completed with the Statistica 5.0 program. The total crude wax yields averaged 0.31% w.w-1 dried leaves for Butia samples and 0.28% for Syagrus samples. The linear hydrocarbons represented on average 15% of the total waxes in the case of Butia samples and 13.7% in Syagrus samples. Hentriacontane and triacontane were the main components of all samples. The comparison of the means showed significant differences among Butia and Syagrus samples, and amongst Butia samples collected in different localities. In the case of the Syagrus collections no consistent groupings could be made. In the case of Butia samples the formation of three groupings could be observed, which were consistent with the species described for their geographical distribution. These results are discussed in the paper.

Use of palmae wax hydrocarbon fractions as chemotaxonomical markers in Butia and Syagrus / Uso de frações de hidrocarbonetos de palmeiras como marcadores quimiotaxonômicos em Butia e Syagrus

The wax hydrocarbon fractions of native Butia and Syagrus species collected from Palms in different regions of the of Rio Grande do Sul state (Brazil) and in Rocha (Uruguay) were analyzed to evaluate their potential as chemotaxonomic markers. The wax was extracted with chloroform and the resulting wax was fractionated by preparative TLC. The hydrocarbon fractions were analyzed by GC-MS. Statistical analyses were completed with the Statistica 5.0 program. The total crude wax yields averaged 0.31% w.w–1 dried leaves for Butia samples and 0.28% for Syagrus samples. The linear hydrocarbons represented on average 15% of the total waxes in the case of Butia samples and 13.7% in Syagrus samples. Hentriacontane and triacontane were the main components of all samples. The comparison of the means showed significant differences among Butia and Syagrus samples, and amongst Butia samples collected in different localities. In the case of the Syagrus collections no consistent groupings could be made. In the case of Butia samples the formation of three groupings could be observed, which were consistent with the species described for their geographical distribution. These results are discussed in the paper.

Frações de hidrocarbonetos das ceras de espécies nativas de Butia e Syagrus coletadas de palmeiras em diferentes regiões do Rio Grande do Sul (Brasil) e em Rocha (Uruguai) foram analisadas para avaliar o seu potencial como marcadores quiomiotaxonômicos. As ceras foram extraídas com clorofórmio e fracionadas por TLC preparativo. As frações de hidrocarbonetos foram analisadas por CG-EM. As análises estatísticas foram realizadas com auxílio do programa Statistica 5.0. O rendimento total de cera das folhas secas foi de 0,31% g.g–1 para as amostras de Butia e de 0,28% para Syagrus. Os hidrocarbonetos lineares representaram em média 15 e 13% do total das ceras para Butia e Syagrus, respectivamente. Hentriacontano e triacontano foram os compostos majoritários em todas as amostras. A comparação de médias mostrou diferenças significativas entre as amostras de Butia e Syagrus e entre as amostras de Butia coletadas em diferentes localidades. As amostras de Syagrus não formaram agrupamentos relacionados com os locais de coleta. Já no caso de Butia, três agrupamentos puderam ser observados e são consistentes com a distribuição geográfica desta espécie. Estes resultados são discutidos no trabalho.

Design, synthesis, and biological evaluation of a series of simple and novel potential antimalarial compounds.

A series of compounds bearing an endocyclic -N-O- moiety with potential antimalarial activity based on simple derivatives of the tropolone purpurogallin was prepared by means of a hetero Diels-Alder reaction using nitrosobenzene as a dienophile. The rationale behind the design of these compounds is presented, together with the synthetic route to derivatives bearing aromatic and aliphatic esters of the C4'-position hydroxyl group of the purpurogallin framework, as well as biological data obtained from in vitro assays against Plasmodium falciparum and Trypanosoma cruzi. Several of the new compounds have activities in the 3-9 microM range, and provide leads for the development of a novel class of antiparasitic drugs with improved biological and pharmacological properties.

Determination of the phospholipid/lipophilic compounds ratio in liposomes by thin-layer chromatography scanning densitometry.

The determination of the ratio of phospholipid/lipophilic compounds in liposomes was achieved after thin-layer chromatography (TLC) by measuring the spot intensities of dipalmitoyl phosphatidylcholine and the lipophilic compound. The liposome components under study were separated on one TLC plate, developed in two steps, and detected after charring the plate with specific visualization reagents. The method shows good reproducibility and provides a simple way to quantify the level of lipophilic compound incorporated in the liposome bilayer.

Chemical basis of the resistance of barley seeds to pathogenic fungi.

The 5-(n)-alkylresorcinol fraction of the epicuticular waxes of Hordeum vulgare seeds appeared to be responsible for their in-born resistance to pathogenic fungi such as Aspergillus niger and Penicillium crysogenum. The antifungal properties of this fraction were evaluated qualitatively and quantitatively with a novel bioassay where the extreme lipophilicity of these compounds was taken into account. The minimum inhibitory concentration in the fungi tested ranged from 5.6 to 10 micrograms cm-2 for the alkyresorcinols. The behaviour of the different cultivars against these fungi could be predicted by measuring the natural amount of resorcinols of each variety by TLC-scanning densitometry. The ranking of cultivars thus established correlated well with the field behaviour of each cultivar, providing a useful and rapid method for predicting the behaviour against fungi of new varieties being developed.