《Arabian Journal of Chemistry》2020,13(10):7289-7301

Black pepper oils have been investigated frequently in the recent years. However, there is a significant variation in physicochemical properties and bioactivity of oils depended on extraction techniques. In this study, the systemic investigation of four various extraction methods was performed to evaluate the physicochemical characterizations, antioxidant and antibacterial activity. The investigation of ¹H NMR, FTIR and UV–Vis spectra confirmed presence of non-volatile components in oils extracted through supercritical CO₂ and hexane-soaking extractions which induced their typical thermal properties. The isothermal behaviour of extracted oils related to evaporation was within range of 3.2–7.3% (w/w) at 27 °C. The SEM images of the black pepper confirmed different operation manners of mechanism between extractions using the solvents and heating process. The lowest MIC for both essential oils from conventional hidrodistillation and microwave-assisted hidrodistillation against two bacteria including E. coli and B. subtilis were found to be 137 µg mL⁻¹. The non-isothermal decomposition kinetics were investigated on the essential oil of microwave-assisted hydrodistillation extraction. The activation energies and pre-exponent factors of non-isothermal decomposition were found to be in range of 36.5–73.7 KJ mol⁻¹ and 4.98 × 10³–1.97 × 10⁸ s⁻¹, respectively, dependent on conversional fractions of the oil. The results revealed that chemical components, physicochemical properties and bioactivity of black pepper essential oils depended on the extraction techniques.  相似文献   

    

《Arabian Journal of Chemistry》2020,13(12):8848-8887

Phthalocyanine (Pc) complexes are an important class of dyes with numerous (e.g., biological, photophysical, and analytical) applications. Among the methods used to improve the properties of these complexes, one should mention the introduction of different substituents, variation of the central metal ion, ligand exchange, and conjugation to nanomaterials (e.g., carbon-based nanomaterials and metal nanoparticles (NPs)). This work briefly reviews Pc complex conjugation to Ag and Au NPs, highlights the different NP shapes, and discusses the diversity of conjugation approaches. Moreover, the use of UV–Vis spectroscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, atomic force microscopy, dynamic light scattering and Fourier transform infrared spectroscopy to characterize Pc-NP hybrids is summarized. The effect of conjugation on Pc photo-physicochemical properties (fluorescence, singlet oxygen generation, triplet state formation, and optical limiting behavior) is discussed, and future perspectives for the synthesis and applications of new hybrids are provided.  相似文献   

    

《Polymer Testing》2020

Two main issues are essential nowadays for practitioners in the field of polymeric materials: how a polymer will behave under dynamic loading conditions and for how long a polymer is reliable. In this sense, the time-temperature superposition principle was applied to the main viscoelastic properties (E′, E″ and tan δ) of a series of polyurethane coatings (PU-DEG-TMP) tested for mechatronic devices. Polyurethanes are derived from an ester glycol (poly(ethylene adipate) glycol), an aromatic diisocyanate (4,4′-dibenzyldiisocyanate) and di/trifunctional chain extenders - diethylene glycol (DEG) and trimethylol propane (TMP). Despite polyurethane intrinsic rheologic complexity, the moduli/loss factor curves superimpose well over several decades of reduced frequency at the glass transition temperature (T_g), 0 °C and 15 °C, the last temperature being considered the midpoint of the practical testing range. Three criteria were for checking the applicability of the time-temperature superposition: the Cole-Cole plot, the similarity between the a_T calculated from both moduli (E′, E″) and the visual appearance of the final master curve. The presence of both hydrogen bonding and chemical joint points, along with some dangling chains put in a broader context the discussion of the microstructural features resulted from the application of the William-Landell-Ferry (WLF) equation.  相似文献   

    

《Polymer Testing》2020

It is elementary to recognize the benefits and the negative impacts of the use of plastic materials on modern societies. Polyethylene (PE) is the major plastic component present in the municipal solid waste. In this paper, two types of low-density PE (LDPE) waste with different mechanical recycling stress histories were used to investigate the influence of recycling cycles on pyrolysis. The kinetic triplet and thermal degradation study were obtained using TGA data.To determine the sample composition and hydrocarbon arrangements, ultimate, proximate and X-ray diffraction analyses were carried out. Taking advantage of these analyses and combining them with differential scanning calorimetry (DSC) data, a series–parallel pyrolysis pathway was formulated. The waste of recycled polyethylene presented low enthalpy of pyrolysis, at about 205 J/g against 299 J/g for a virgin PE. The DSC analyses evidenced a multi-step reaction behavior of the pyrolysis, confirmed by the kinetic study using different isoconversional methods: the waste of recycled polyethylene presented a higher variation of activation energies as a function of the fraction reacted. The main conclusion is that the results suggest that the recycling stress history promotes the increase of long carbon chains while weakening the boundary among the compounds. This explains the fact that recycled waste needs less activation energy than other samples to degrade thermally. Finally, different categories of low-density polyethylene wastes must be considered when dealing with either kinetics or modeling of the product recovery process.  相似文献   

    

《Polymer Testing》2020

In this study, a simple chemical precipitation method was used to synthesize ZnO: Co²⁺ as nanoparticles. The solution casting technique was used for the preparation of polymer films of Carboxymethyl cellulose (CMC) doped with different contents (0.5, 1.5, 3, and 5 wt%) of ZnO/Co NPs. As shown by the X-ray diffraction, the average size of ZnO/Co crystallite of the NPs is 25.6 nm. Meanwhile, the addition of ZnO/Co reduced the semi-crystallinity of CMC. The Fourier transform infrared (FTIR) confirmed the interaction between the ZnO/Co NPs and the polymer CMC. The direct and indirect band gap (Eg) was reduced from (5.32–5.01 eV and 5.20 to 4.99 eV respectively) with the increase in ZnO/Co NPs content up to 3 wt% after this content the Eg is increased as shown by the UV–Vis spectra. In addition, the results of TGA displayed the decomposition of the nanocomposite to be little compared to that of the pure CMC indicating the success of fabrication of products. The improvement of the ionic conductivity was noticed upon the addition of ZnO/Co NPs into the polymer CMC system which can be explained in terms of an increase in amorphicity as shown by the impedance spectroscopic study. It was found that the optimum ionic conductivity (3.209 × 10⁻⁶ Scm⁻¹) at ambient temperature was higher for the sample containing 1.5 wt% ZnO/Co NPs with highest of amorphicity and the lowest total loss of weight. Therefore, the improvements in optical properties, thermal stability, and AC conductivity which were observed represent a strong support for the use of the nanocomposite films in the solid state battery applications.  相似文献   

    

《Polymer Testing》2020

This study is focused on numerical investigation on fracture behaviors of carbon black (CB) and silica filled elastomeric composites. Finite element analysis (FEA) in compliance with multi-specimen method is used to calculate J-integral and geometry factor of the rubber composites up to a displacement of 20 mm for single edge notch in tension (SENT) and double edge notch in tension (DENT) specimens. An empirical relationship between crack tip opening displacement (CTOD) and crack advancement is established depending on notch to width ratio (NWR). The stress contours across the notches for SENT and DENT specimens is discussed briefly. It is found that fracture propagation resistance of CB filled elastomer is 125% more than that of silica filled elastomer. Although, Silica filled elastomer have good tensile strength and crosslink density but it fails to replace carbon black in terms of fracture properties. The critical J-integral for CB filled elastomer is 18.7% and 32.2% more than silica filled elastomer for SENT and DENT specimens respectively. The effect of specimen type on various fracture properties is also explored. The factor of safety is found to be significantly more in case of CB filled elastomers making them less vulnerable to crack propagation and catastrophic failure.  相似文献   

    

Marta Klimek-Szczykutowicz  Micha&#x; Dziurka  Ivica Blaevi&#x;  Azra &#x;ulovi&#x;  Sebastian Granica  Izabela Korona-Glowniak  Halina Ekiert  Agnieszka Szopa 《Molecules (Basel, Switzerland)》2020,25(22)

The main compounds in both extracts were gluconasturtiin, 4-methoxyglucobrassicin and rutoside, the amounts of which were, respectively, determined as 182.93, 58.86 and 23.24 mg/100 g dry weight (DW) in biomass extracts and 640.94, 23.47 and 7.20 mg/100 g DW in plant herb extracts. The antioxidant potential of all the studied extracts evaluated using CUPRAC (CUPric Reducing Antioxidant Activity), FRAP (Ferric Reducing Ability of Plasma), and DPPH (1,1-diphenyl-2-picrylhydrazyl) assays was comparable. The anti-inflammatory activity of the extracts was tested based on the inhibition of 15-lipoxygenase, cyclooxygenase-1, cyclooxygenase-2 (COX-2), and phospholipase A₂. The results demonstrate significantly higher inhibition of COX-2 for in vitro cultured biomass compared with the herb extracts (75.4 and 41.1%, respectively). Moreover, all the studied extracts showed almost similar antibacterial and antifungal potential. Based on these findings, and due to the fact that the growth of in vitro microshoots is independent of environmental conditions and unaffected by environmental pollution, we propose that biomass that can be rapidly grown in RITA^® bioreactors can serve as an alternative source of bioactive compounds with valuable biological properties.  相似文献   

    

Immacolata Faraone  Fabiana Labanca  Maria Ponticelli  Nunziatina De Tommasi  Luigi Milella 《Molecules (Basel, Switzerland)》2020,25(22)

The rapid spread of the new Coronavirus Disease 2019 (COVID-19) has actually become the newest challenge for the healthcare system since, to date, there is not an effective treatment. Among all drugs tested, Hydroxychloroquine (HCQ) has attracted significant attention. This systematic review aims to analyze preclinical and clinical studies on HCQ potential use in viral infection and chronic diseases. A systematic search of Scopus and PubMed databases was performed to identify clinical and preclinical studies on this argument; 2463 papers were identified and 133 studies were included. Regarding HCQ activity against COVID-19, it was noticed that despite the first data were promising, the latest outcomes highlighted the ineffectiveness of HCQ in the treatment of viral infection. Several trials have seen that HCQ administration did not improve severe illness and did not prevent the infection outbreak after virus exposure. By contrast, HCQ arises as a first-line treatment in managing autoimmune diseases such as rheumatoid arthritis, lupus erythematosus, and Sjögren syndrome. It also improves glucose and lipid homeostasis and reveals significant antibacterial activity.  相似文献   

    

Qamar Uddin Ahmed  Abdul Hasib Mohd Ali  Sayeed Mukhtar  Meshari A. Alsharif  Humaira Parveen  Awis Sukarni Mohmad Sabere  Mohamed Sufian Mohd. Nawi  Alfi Khatib  Mohammad Jamshed Siddiqui  Abdulrashid Umar  Alhassan Muhammad Alhassan 《Molecules (Basel, Switzerland)》2020,25(23)

In recent years, there is emerging evidence that isoflavonoids, either dietary or obtained from traditional medicinal plants, could play an important role as a supplementary drug in the management of type 2 diabetes mellitus (T2DM) due to their reported pronounced biological effects in relation to multiple metabolic factors associated with diabetes. Hence, in this regard, we have comprehensively reviewed the potential biological effects of isoflavonoids, particularly biochanin A, genistein, daidzein, glycitein, and formononetin on metabolic disorders and long-term complications induced by T2DM in order to understand whether they can be future candidates as a safe antidiabetic agent. Based on in-depth in vitro and in vivo studies evaluations, isoflavonoids have been found to activate gene expression through the stimulation of peroxisome proliferator-activated receptors (PPARs) (α, γ), modulate carbohydrate metabolism, regulate hyperglycemia, induce dyslipidemia, lessen insulin resistance, and modify adipocyte differentiation and tissue metabolism. Moreover, these natural compounds have also been found to attenuate oxidative stress through the oxidative signaling process and inflammatory mechanism. Hence, isoflavonoids have been envisioned to be able to prevent and slow down the progression of long-term diabetes complications including cardiovascular disease, nephropathy, neuropathy, and retinopathy. Further thoroughgoing investigations in human clinical studies are strongly recommended to obtain the optimum and specific dose and regimen required for supplementation with isoflavonoids and derivatives in diabetic patients.  相似文献   

    

Marvin Mhler  Katharina Hfer  Andres Jschke 《Molecules (Basel, Switzerland)》2020,25(23)

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