Binding Properties of Photosynthetic Herbicides: Photosynthetic Activity and Molecular Docking Approach towards 1,4-Dihydropyridines Derivatives.

In the current work, we describe the synthesis of 1,4-dihydropyridine (1,4-DHP) derivatives via Hantzsch multicomponent reaction and their evaluation as photosystem II (PSII) inhibitors through chlorophyll a fluorescence bioassay. Among all the compounds tested, 1,1'-(2,4,6-trimethyl-1,4-dihydropyridine-3,5-diyl)bis(ethan-1-one) (4b) showed best results, reducing the parameters performance index on absorption basis (PIabs ) and electron transport per reaction center by 61 % and 49 %, respectively, as compared to the control. These results indicate the inhibitory activity of PSII over the electron transport chain. Additionally, a molecular docking approach using the protein D1 (PDB code 4V82) was performed in order to assess the structure-activity relationship among the 1,4-DHP derivatives over the PSII, which revealed that both, size of the group at position 4 and the carbonyl groups at the dihydropyridine ring are important for the ligand's interaction, particularly for the hydrogen-bonding interaction with the residues His215, Ser264, and Phe265. Thus, the optimization of these molecular features is the aim of our research group to extend the knowledge of PSII electron chain inhibitors and the establishment of new potent bioactive molecular scaffolds.

Metabolomic Analysis of Combretum lanceolatum Plants Interaction with Diaporthe phaseolorum and Trichoderma spirale Endophytic Fungi through 1 H-NMR.

Endophytic fungi are an important class of microorganisms, able to interact with a host plant via a mutualistic mechanism without visible symptoms of the fungal colonization. The synergy between endophytic fungi and their host plant can promote morphological, physiological and biochemical changes through the expression of bioactive metabolites. This work aims to correlate metabolic changes in the Combretum lanceolatum plant metabolome with its endophytic fungi Diaporthe phaseolorum (Dp) and Trichoderma spirale (Ts), and to discover corresponding metabolite-biomarkers, with the principal focus being on its primary metabolism. The 1 H-NMR metabolomic analysis of qualitative and quantitative changes was performed through multivariate statistical analysis and the identification of primary metabolites was achieved on the Madison Metabolomics Consortium Database. The presence of Dp significantly impacted the plant's metabolic pathways, improving the biosynthesis of primary metabolites such as threonine, malic acid and N-acetyl-mannosamine, which are precursors of special metabolites involved in plant self-defence. This work represents a valuable contribution to advanced studies on the metabolic profiles of the interaction of plants with endophytes.

Endophytic fungal extracts: evaluation as photosynthesis and weed growth inhibitors.

A central pillar of modern weed control is the discovery of new herbicides which are nontoxic to humans and the environment and which have low application dosage. The natural products found in plants and microorganisms are well suited in this context because they are generally nontoxic and have a wide variety of biological activities. In this work, Diaporthe phaseolorum (Dp), Penicillium simplicissimum (Ps) and Trichoderma spirale (Ts) (methanolic extracts) were evaluated as photosynthesis and plant growth inhibitors in Senna occidentalis and Ipomoea grandifolia. The most significant results were observed for Ts and Dp in S. occidentalis and I. grandifolia, respectively. Ts reduced PI(abs), ET0/CS0, PHI(E0) and PSI0 parameters by 64, 28, 40 and 38%, respectively, indicating a reduction on electron transport efficiency. Additionally, Ts decreased shoot length by 9%, affecting the plant growth. Dp reduced PI(abs), ET0/CS0 and PHI(E0) parameters by 50, 20, 26 and 22%, respectively, revealing the inhibition competency on PSII acceptor site. Furthermore, Dp decreased by 50% the shoot length on germination assay. Thus, the phytotoxic behaviors based on endophytic fungal extracts may serve as a valuable tool in the further development of a bioherbicide since natural products represent an interesting alternative to replace commercial herbicides.

Measuring dielectric properties for microwave-assisted extraction of essential oils using single-mode and multimode reactors.

The dielectric properties of Cymbopogon nardus, Eucalyptus sp., Piper aduncum and Piper hispidinervum were investigated as a function of frequency and temperature, using dry plant matter and its mixtures with water at different concentrations. This was followed by the extraction of essential oils performed with microwave heating in single-mode and multimode cavities with a variable power 6.0 kW generator operating at 2.45 GHz. The dielectric properties of the dry plant matter changed markedly with increasing water content, exhibiting high loss factors and small penetration depths. Due to the high level of absorption, even with low water contents, microwave-assisted extraction (MAE) showed better green performance employing lower plant matter/water ratios (1 : 2 or 1 : 4) and applying shorter extraction times compared with conventional hydrodistillation (HD). Using the single-mode MAE reactor, in the case of Cymbopogon nardus, for a plant matter/water ratio of 1 : 4 the energy efficiency was 1.78 g kW-1 h-1, applying 0.3 kW for 16.7 min. By way of comparison, for the same extraction time using HD, the corresponding efficiency was only 0.50 g kW-1 h-1. In experiments with citronella using multimode MAE, the best energy efficiency of 2.53 g kW-1 h-1 was obtained with a plant matter/water ratio of 1 : 2 applying 1.8 kW of power for 30 min. Single and multimode MAE experiments showed optimum conditions with lower water content. Thus, greater amounts of material can be processed in a shorter time, in accordance with the ideals of a green chemistry. The resulting extractions showed an energy efficiency up to 27 times greater compared with conventional HD, applying the same extraction time.

Isovitexin as marker and bioactive compound in the antinociceptive activity of the Brazilian crude drug extracts of Echinodorus scaber and E. grandiflorus

Abstract Echinodorus scaber Rataj and Echinodorus grandiflorus (Cham. & Schltdl.) Micheli, Alismataceae, are popularly used to relieve inflammatory complaints and as diuretic. A study on the antinociceptive effect and selected marker compounds in eleven extracts from different locations was undertaken and their antinociceptive effect was assessed. The fingerprints were compared by HPLC-DAD and the content of vitexin, isovitexin, isoorientin and vitexin-2-O-rhamnoside were determined. All samples presented antinociceptive activity reducing the writhes by 36.4-62.5% and 47.4-79.8% at 10 and 50 mg/kg, respectively; indomethacin (5 mg/kg) reduced writhes by 82.6-90.1%. The content of the flavonoids C-glycosides, however, presented a strong variation. Isovitexin and isoorientin were found in all the samples, with content ranging from traces to 14.70 µg/mg and 2.12-84.27 µg/mg extract, respectively, while vitexin-2-O-rhamnoside occurred in quantifiable amounts only in 3 out of 11 samples ranging from 5.43 to 33.13 µg/mg extract; vitexin was not detected at all or detected in trace amounts. According to the fingerprints, the samples could be arranged in four main groups. All eleven extracts showed antinociceptive activity. Isovitexin was the only flavonoid present in all samples and can be regarded, acting in synergy with the other compounds or not, as the responsible for the antinociceptive activity. Therefore, isovitexin is a good choice as chemical marker when the antinociceptive activity of E. scaber and E. grandiflorus is investigated.

Quantum Tunneling Contribution for the Activation Energy in Microwave-Induced Reactions.

In this study, a quantum approach is presented to explain microwave-enhanced reaction rates by considering the tunneling effects in chemical reactions. In the Arrhenius equation, the part of the Hamiltonian relative to the interaction energy during tunneling, between the particle that tunnels and the electrical field defined in the medium, whose spatial component is specified by its rms value, is taken into account. An approximate evaluation of the interaction energy leads to a linear dependence of the effective activation energy on the applied field. The evaluation of the rms value of the field for pure liquids and reaction mixtures, through their known dielectric properties, leads to an appreciable reduction in the activation energies for the proton transfer process in these liquids. The results indicate the need to move toward the use of more refined methods of modern quantum chemistry to calculate more accurately field-induced reaction rates and effective activation energies.

Measurement of Dielectric Properties and Microwave-Assisted Homogeneous Acid-Catalyzed Transesterification in a Monomode Reactor.

Microwave heating technology is dependent on the dielectric properties of the materials being processed. The dielectric properties of H2SO4, H3PO4, ClSO3H, and H3CSO3H were investigated in this study using a vector network analyzer in an open-ended coaxial probe method at various temperatures. Phosphoric and sulfuric acids presented higher loss tangents in the frequency range 0.3-13 GHz, reflecting greater mobility of the ions and counterions. The acids were employed as catalysts in microwave-assisted homogeneous transesterification reactions for the production of methylic and ethylic biodiesel. The effects of catalyst concentration, alcohol to oil molar ratio, and irradiation time on biodiesel conversions were investigated. The results showed a significant reduction in the reaction time for microwave-assisted transesterification reactions as compared to times for conventional heating. Also, despite its higher loss tangent, it was observed that H3PO4 leads to lower conversion to biodiesel, which can be explained by its lower carbonyl protonation capacity.

Gênero Acosmium: composição química e potencial farmacológico: [revisão] / Acosmium genus: chemical composition and pharmacological potential: [review]

O gênero Acosmium possui 17 espécies com distribuição geográfica que se estende do sudeste do México até o Nordeste da Argentina, sendo que a maioria das espécies está localizada no Brasil. A. dasycarpum, A. panamense, A. subelegans são as espécies mais utilizadas popularmente no tratamento de enfermidades. Uma busca na literatura, resguardando aspectos químicos e farmacológicos destas plantas, indicam atividade citotóxica, ação antitérmica, efeito hipoglicêmico, bem como tem sido usada no tratamento da doença de Alzheimer e desordens no sistema nervoso central. Investigação fitoquímica resultou principalmente no isolamento de terpenos, ácido cafêico, alcalóides do tipo diaza-adamantano e quinolizidínicos bem como pironas.

The genus Acosmium is composed by c.a. 17 species, with geographic distribution from southeastern Mexico to Northwestern Argentina. Most of the species, however, are located in Brazil. A. dasycarpum, A. panamense, A. subelegans are used in folk medicine to treat several ailments. A search in the literature regarding the chemical and pharmacological aspects of these plants indicates cytotoxic activity, antithermal and hypoglycemic effects, as well as their use to treat Alzheimer's disease and CNS disorders. Phytochemical investigations resulted mainly in the isolation of terpenes, caffeic acid, diaza-adamantane and quinolizidines alkaloids as well as pyrones.