Secondary Metabolites,including a New 5,6-Dihydropyran-2-One,Produced by the Fungus Diplodia corticola. Aphicidal Activity of the Main Metabolite,Sphaeropsidin A

An undescribed 5,6-dihydropyran-2-one, namely diplopyrone C, was isolated and characterized from the cultures of an isolate of the fungus Diplodia corticola recovered from Quercus suber in Algeria. The structure and relative stereostructure of (5S,6S,7Z,9S,10S)-5-hydroxy-6-(2-(3-methyloxiran-2-yl)vinyl)-5,6-dihydro-2H-pyran-2-one were assigned essentially based on NMR and MS data. Furthermore, ten known compounds were isolated and identified in the same cultures. The most abundant product, the tetracyclic pimarane diterpene sphaeropsidin A, was tested for insecticidal effects against the model sucking aphid, Acyrthosiphon pisum. Results showed a toxic dose-dependent oral activity of sphaeropsidin A, with an LC₅₀ of 9.64 mM.     

Antioxidant Potential and Enhancement of Bioactive Metabolite Production in In Vitro Cultures of Scutellaria lateriflora L. by Biotechnological Methods

Studies carried out using three different in vitro assays and a biological setting (Escherichia coil) demonstrated the antioxidant activity of Scutellaria lateriflora microshoot extract. Moreover, the extract exhibited no toxicity in a brine shrimp lethality bioassay. These results indicated that microshoots are a rich, safe source of antioxidants, which encouraged us to enhance their production in vitro. In agar and agitated cultures, two biotechnological strategies were applied: feeding the cultures with the biogenetic precursors of the phenolics—phenylalanine and tyrosine, and eliciting them with methyl jasmonate. Specific Scutellaria flavonoids and verbascoside were analysed by HPLC. Feeding with precursors (1 g/L) in agar cultures decreased the production of the metabolites. In agitated cultures, different concentrations of precursors (1.0–2.5 g/L) and the elicitor (10; 50; 100 µM) were tested. Additionally, parallel feeding with the precursor and elicitor in a concentration of 50 µM were applied. The best strategy for total flavonoid and verbascoside production was phenylalanine feeding (1.5 g/L), max. 3765 and 475 mg/100 g DW, respectively, after 7 days. This is the first report documenting the high antioxidant production in S. lateriflora microshoots after feeding with phenylalanine. Moreover, for the first time, bioreactor cultures were successfully maintained, obtaining attractive results (max. total flavonoid content 2348 and verbascoside 485 mg/100 g DW).     

Chemical Composition and Evaluation of Insecticidal Activity of Calendula incana subsp. maritima and Laserpitium siler subsp. siculum Essential Oils against Stored Products Pests

The problems of the environment and human health related to the use of synthetic and broad-spectrum insecticides have increasingly motivated scientific research on different alternatives and among these, the use of green systems, such as essential oils, have been explored. Several species of the Apiaceae and Asteraceae families, aromatic herbs rich in secondary bioactive metabolites, are used in the industrial field for pharmaceutical, cosmetic, and food purposes. Different essential oils extracted from some species of these families have shown acute toxicity and attractive and/or repellent effects towards different insects. In our work, we investigated the toxic potential of Calendula incana subsp. maritima and Laserpitium siler subsp. siculum essential oils against four insect species, Sitophilus oryzae, Lasioderma serricorne, Necrobia rufipes, and Rhyzoperta dominica, which are common pests of stored products. The composition of both oils, extracted by hydrodistillation from the aerial parts of the two plants, was evaluated by GC×GC-MS. Calendula incana subsp. maritima essential oil was rich in oxygenated sesquiterpenoids, such as cubebol (35.39%), 4-epi-cubebol (22.99%), and cubenol (12.77%), while the Laserpitium siler subsp. siculum essential oil was composed mainly of monoterpene hydrocarbons, such as β-phellandrene (42.16%), limonene (23.87%), and β-terpinene (11.80%). The toxicity Petri dish bioassays indicated that C. maritima oil killed a mean of 65.50% of S. oryzae and 44.00% of R. dominica adults, indicating a higher biocidal activity in comparison with L. siculum oil, while toward the other species, no significant differences in mortality were recorded. Calendula maritima oil could be, then, considered a promising candidate for further tests as an alternative biocide toward S. oryzae and R. dominica. The possibility that the relatively high content of oxygenated sesquiterpenoids in C. maritima essential oil determines its higher biocidal activity is discussed.     

Thermal degradation of poly(p-methylstyrene)

The thermal degradation behaviour, in the absence of oxygen, of poly(p-methylstyrene) has been investigated. Monomer is the main product formed in the degradation process, together with different oligomers which have been identified and whose amounts have been determined. A reaction mechanism accounting for the formation of the degradation products, and similar to the mechanism established for polystyrene, is proposed. The main differences of the process comparing with polystyrene are the higher amount of monomer which is produced and the crosslinking structures which are formed at T < 400° C.     

Bimodal Fluorescence/Magnetic Resonance Molecular Probes with Extended Spin Lifetimes

Bimodal molecular probes combining nuclear magnetic resonance (NMR) and fluorescence have been widely studied in basic science, as well as clinical research. The investigation of spin phenomena holds promise to broaden the scope of available probes allowing deeper insights into physiological processes. Herein, a class of molecules with a bimodal character with respect to fluorescence and nuclear spin singlet states is introduced. Singlet states are NMR silent but can be probed indirectly. Symmetric, perdeuterated molecules, in which the singlet states can be populated by vanishingly small electron-mediated couplings (below 1 Hz) are reported. The lifetimes of these states are an order of magnitude longer than the longitudinal relaxation times and up to four minutes at 7 T. Moreover, these molecules show either aggregation induced emission (AIE) or aggregation caused quenching (ACQ) with respect to their fluorescence. In the latter case, the existence of excited dimers, which are proposed to use in a switchable manner in combination with the quenching of nuclear spin singlet states, is observed     

Probing the Intracellular Glutathione Redox Potential by In‐Cell NMR Spectroscopy

Non‐invasive and real‐time analysis of cellular redox processes has been greatly hampered by lack of suitable measurement techniques. Here we describe an in‐cell nuclear magnetic resonance (NMR) based method for measuring the intracellular glutathione redox potential by direct and quantitative measurement of isotopically labeled glutathione introduced exogenously into living yeast. By using this approach, perturbations in the cellular glutathione redox homeostasis were also monitored as yeast cells were subjected to oxidative stress.     

Determination of maize and grain herbicides and their transformation products in soil by use of soil column extraction then liquid chromatography with tandem mass spectrometry

Summary A multiresidue method has been developed for identification and quantitation of the herbicides most commonly used in cultivation of maize and grain, and of their transformation products, in soil samples. The analytes were isolated by soil column extraction (SCE) and the extracts were purified by use of a Carbograph-1 cartridge. Analysis was performed by liquid chromatography coupled with tandem mass spectrometric detection (LC-TISP-MS-MS) in negative-ion mode. To optimize the extraction conditions affecting the performance of SCE, e.g. the extracting solvent used, temperature, extracting volume, and solvent flow rate, were studied. To evaluate the matrix effect in SCE, recovery experiments were performed on soil samples, with different physical and chemical characteristics, fortified with the 100 ng g⁻¹ of the target compounds. Recovery data were satisfactory and the method detection limits were between 3 and 100 ng g⁻¹, depending on the compound.     

Relaxed representations and improving stability in time-stepping analysis of three-dimensional structural nonlinear dynamics

In the present paper, we propose a representation of the discrete motion equations in structural nonlinear dynamics to obtain an improvement in the stability of time numerical integrations. A geometrically nonlinear total Lagrangian formulation for three-dimensional beam elements in the hypotheses of large rotations and small strains is presented. In this formulation, slopes are used instead of rotation parameters to compute the nonlinear representations of the strain measures in the inertial frame of reference. Such representations of the internal strains??rotations compatibility are then imposed in their time derivatives version. The results, related to Newmark approximations for the variations in the displacement and velocity vectors, show a significant increase in the range of stability of the time integration process and a reduction in the number of Newton iterations required in the time integration steps. The numerical tests, furthermore, show that the variation in the total energy in the time steps has bounded oscillations about the zero value.