The role of nanocellulose fibers, starch and chitosan on multipolysaccharide based films

Thin nanocomposite films of thermoplastic starch, chitosan and cellulose nanofibers (bacterial cellulose or nanofibrillated cellulose) were prepared for the first time by solvent casting of water based suspensions of the three polysaccharides. The role of the different bioploymers on the final properties (thermal stability, transparency, mechanical performance and antimicrobial activity) of the films was related with their intrinsic features, contents and synergic effects resulting from the establishment of interactions between them. Thermoplastic starch displays an important role on the thermal stability of the films because it is the most stable polysaccharide; however it has a negative impact on the mechanical performance and transparency of the films. The addition of chitosan improves considerably the transparency (up to 50 % transmittance for 50 % of chitosan, in respect to the amount of starch), mechanical performance and antimicrobial properties (at least 25 % of chitosan and no more than 10 % of cellulose nanofibers are required to observe bacteriostatic or bactericidal activity) but decrease their thermal stability. The incorporation of cellulose nanofibers had the strongest positive impact on the mechanical properties of the materials (increments of up to 15 and 30 MPa on the Young′s modulus and Tensile strength, respectively, for films with 20 % of BC or NFC). Nonetheless, the impact in thermal stability and mechanical performance of the films, promoted by the addition of chitosan and cellulose nanofibres, respectively, was higher than the expected considering their percentage contents certainly because of the establishment of strong and complex interactions between the three polysaccharides.     

Cellulose/iron oxide hybrids as multifunctional pigments in thermoplastic starch based materials

Cellulose/iron oxide hybrids were prepared by the controlled hydrolysis of FeC₂O₄ in the presence of vegetable and bacterial cellulose fibres as substrates. By varying the relative amount of FeC₂O₄ and NaOH, either hematite or magnetic iron oxides were grown at the cellulose fibres surfaces. This chemical strategy was used for the production of a number of materials, whose coloristic properties associated to their reinforcement role allowed their use as new hybrid pigments for thermoplastic starch (TPS) based products. The TPS reinforced materials were characterized by several techniques in order to evaluate: the morphology and the compatibility between the matrix and the fillers; the mechanical reinforcement effect of the cellulose/iron oxide pigments on TPS and the coloristic properties of the composites. All materials showed good dispersion and strong adhesion for the cellulose/iron oxide nanocomposites in the TPS matrix thus resulting in improved mechanical properties.     

Synthesis of 3-iodothiophenes via iodocyclization of (Z)-thiobutenynes

A simple synthesis of 3-iodothiophenes was demonstrated using a wide range of (Z)-thioenynes. The key step in the iodocyclofunctionalization was the selective reduction of the triple bond in (Z)-thioenynes by the addition of iodine as an electrophilic agent. The 3-iodothiophenes were obtained in good to excellent yields of 61–92%. The 3-iodothiophenes were used as substrates in Sonogashira cross-coupling reactions to obtain thiophene acetylenes.     

Evaluation of As,Se and Zn in octopus samples in different points of sales of the distribution chain in Brazil

Three CRMs of different matrix composition were analysed, representing an environmental matrix sample (BCR–320R Channel Sediment), a botanical matrix sample (SRM 1547 Peach Leaves) and a zoological matrix sample (SRM 1566b Oyster Tissue). The element mass fractions were obtained using the KayWin program. Analytical measurement uncertainty was determined by two approaches: (1) the routine procedure applying combination of the overall uncertainty u(m) = 3.5 % and statistical uncertainty of the peak area determination and (2) the procedure applying the dedicated ERON program for calculating uncertainty. Performance of altogether 31 certified values was tested by means of calculating E _n numbers. For the remaining 52 non-certified values, comparison between uncertainties obtained by the two approaches was made. When using the first approach, the E _n number showed satisfactory performance in 28 cases; by using the second approach, the E _n number showed satisfactory performance in 27 cases. None of the unsatisfactory performances (E _n  > 1) appeared to be of systematic nature. The uncertainties obtained by applying the two approaches revealed a big extent of consistency. As the present nuclear database lacks lot of data that serve as input to the ERON program, in particular uncertainties of Q ₀ factors, estimates need to be introduced for the missing values, emphasising the urgent need to upgrade the database with missing data.     

Microextraction by packed sorbent liquid chromatography with time‐of‐flight mass spectrometry of triazines employing a molecularly imprinted polymer†

Molecularly imprinted polymers for the determination of triazines were synthesized by precipitation using atrazine as template, methacrylic acid as functional monomer, ethylene glycol dimethacrylate as crosslinker, and 2,2′‐azobisisobutrynitrile as initiator. The polymers were characterized by infrared spectroscopy and scanning electron microscopy and packed in a device for microextraction by packed sorbent aiming for the preconcentration/cleanup of herbicides, such as atrazine, simazine, simetryn, ametryn, and terbutryn in corn samples. Liquid chromatography coupled with time‐of‐flight mass spectrometry was used for the separation and determination of the herbicides. The selectivity coefficient of molecularly imprinted polymers was compared with that of nonimprinted polymer for the binary mixtures of atrazine/propanil and atrazine/picloram, and the values obtained were 15.6 and 2.96, respectively. The analytical curve ranged from 10 to 80 μg/kg (r = 0.989) and the limits of detection and quantification in the corn matrices were 3.3 and 10 μg/kg, respectively. Intra‐ and interday precisions were < 14.8% and accuracy was better than 90.9% for all herbicides. Polymer synthesis was successfully applied to the cleanup and preconcentration of triazines from fortified corn samples with 91.1–109.1% of recovery.     

Evaluation of the effect of silicon on the carbonization process of Colombian semi-anthracites

The environmental impacts associated with the exploitation and transformation of fossil resources aggravate the planet's situation in terms of climate change. Due to this, this paper studies an alternative use of mineral coal as a precursor to obtaining new materials with different properties to the starting coals. The thermal degradation of two Colombian semi-anthracites is analyzed through the thermogravimetry (TG) technique coupled to a Fourier transform infrared spectroscopy (FTIR) equipment from room temperature (25 °C) to 900 °C, at a heating rate of 10 K min^?1 in an inert atmosphere. The catalytic effect of the addition of silicon to these samples before being subjected to a carbonization process is evaluated during this process. The results indicated that the primary reaction occurs in the temperature range between 400 and 680 °C, where the highest mass loss rate was observed. At the end of the heating process, the TG profile of the samples with silicon addition showed losses between 14.33 and 18.82% in mass, these values being slightly higher compared to the starting and demineralized samples. The release of water, light gases such as CO₂, CH₄, and species such as toluene, phenol and formic acid was identified in most of the samples. The presence of silica seems to favor the release of all these species, being more evident in one of the semi-anthracites studied. According to the results obtained, it is proved that the presence of silicon in samples subjected to carbonization processes has a catalytic effect that improves some characteristics of the new materials obtained, thus contributing to the use of carbon to get new materials.

     

New Luminescent Lanthanide Tetrakis-Complexes NEt4[LnL4] Based on Dimethyl-N-Benzoylamidophosphate

New lanthanide dimethyl-N-benzoylamidophosphate (HL) based tetrakis-complexes NEt₄[LnL₄] (Ln³⁺=La, Nd, Sm, Eu, Gd, Tb, Dy) are reported. The complexes are characterized by means of NMR, IR, absorption, and luminescent spectroscopy as well as by elemental, X-Ray, and thermal gravimetric analyses. The phenyl groups of the four ligands of the complex anion are directed towards one side, while the methoxy groups are directed in the opposite side, which makes the complexes under consideration structurally similar to calixarenes. The effect of changing the alkali metal counterion to the organic cation NEt₄⁺ on the structure and properties of the tetrakis-complex [LnL4]^- is analyzed. The complexes exhibit bright characteristic for respective lanthanides luminescence. Rather high intensity of the band of ⁵D₀→⁷F₄ transition, observed in the luminescence spectrum of NEt₄[EuL₄], is discussed based on theoretical calculations.     

Chemical Composition and Antioxidant Activity of Essential Oils from Eugenia patrisii Vahl,E. punicifolia (Kunth) DC., and Myrcia tomentosa (Aubl.) DC., Leaf of Family Myrtaceae

Essential oils (EOs) were extracted from Eugenia patrisii, E. punicifolia, and Myrcia tomentosa, specimens A and B, using hydrodistillation. Gas chromatography coupled with mass spectrometry (GC/MS) was used to identify the volatile constituents present, and the antioxidant capacity of EOs was determined using diphenylpicryl-hydrazyl (DPPH) and trolox equivalent antioxidant capacity (TEAC) assays. For E. patrisii, germacrene D (20.03%), bicyclogermacrene (11.82%), and (E)-caryophyllene (11.04%) were identified as the major constituents of the EOs extracted from specimen A, whereas specimen B primarily comprised γ-elemene (25.89%), germacrene B (8.11%), and (E)-caryophyllene (10.76%). The EOs of E. punicifolia specimen A contained β-Elemene (25.12%), (E)-caryophyllene (13.11%), and bicyclogermacrene (9.88%), while specimen B was composed of (E)-caryophyllene (11.47%), bicyclogermacrene (5.86%), β-pinene (5.86%), and γ-muurolene (5.55%). The specimen A of M. tomentosa was characterized by γ-elemene (12.52%), germacrene D (11.45%), and (E)-caryophyllene (10.22%), while specimen B contained spathulenol (40.70%), α-zingiberene (9.58%), and γ-elemene (6.89%). Additionally, the chemical composition of the EOs was qualitatively and quantitatively affected by the collection period. Furthermore, the EOs of the studied specimens, especially specimen A of E. punicifolia, showed a greater antioxidant activity in DPPH rather than TEAC, as represented by a significantly high inhibition percentage (408.0%).     

Antiprotozoal and Antibacterial Activity of Ravenelin,a Xanthone Isolated from the Endophytic Fungus Exserohilum rostratum

The natural compound ravenelin was isolated from the biomass extracts of Exserohilum rostratum fungus, and its antimicrobial, antiplasmodial, and trypanocidal activities were evaluated. Ravenelin was isolated by column chromatography and HPLC and identified by NMR and MS. The susceptibility of Gram-positive and Gram-negative bacteria strains to ravenelin was determined by microbroth dilution assay. Cytotoxicity was evaluated in hepatocarcinoma cells (HepG2) and BALB/c peritoneal macrophages by using MTT. SYBR Green I-based assay was used in the asexual stages of Plasmodium falciparum. Trypanocidal activity was tested against the epimastigote and intracellular amastigote forms of Trypanosoma cruzi. Ravenelin was active against Gram-positive bacteria strains, with emphasis on Bacillus subtilis (MIC value of 7.5 µM). Ravenelin’s antiparasitic activities were assessed against both the epimastigote (IC₅₀ value of 5 ± 1 µM) and the intracellular amastigote forms of T. cruzi (IC₅₀ value of 9 ± 2 µM), as well as against P. falciparum (IC₅₀ value of 3.4 ± 0.4 µM). Ravenelin showed low cytotoxic effects on both HepG2 (CC₅₀ > 50 µM) and peritoneal macrophage (CC₅₀ = 185 ± 1 µM) cells with attractive selectivity for the parasites (SI values > 15). These findings indicate that ravenelin is a natural compound with both antibacterial and antiparasitic activities, and considerable selectivity indexes. Therefore, ravenelin is an attractive candidate for hit-to-lead development.