Microbial Natural Products with Antiviral Activities,Including Anti-SARS-CoV-2: A Review

The SARS-CoV-2 virus, which caused the COVID-19 infection, was discovered two and a half years ago. It caused a global pandemic, resulting in millions of deaths and substantial damage to the worldwide economy. Currently, only a few vaccines and antiviral drugs are available to combat SARS-CoV-2. However, there has been an increase in virus-related research, including exploring new drugs and their repurposing. Since discovering penicillin, natural products, particularly those derived from microbes, have been viewed as an abundant source of lead compounds for drug discovery. These compounds treat bacterial, fungal, parasitic, and viral infections. This review incorporates evidence from the available research publications on isolated and identified natural products derived from microbes with anti-hepatitis, anti-herpes simplex, anti-HIV, anti-influenza, anti-respiratory syncytial virus, and anti-SARS-CoV-2 properties. About 131 compounds with in vitro antiviral activity and 1 compound with both in vitro and in vivo activity have been isolated from microorganisms, and the mechanism of action for some of these compounds has been described. Recent reports have shown that natural products produced by the microbes, such as aurasperone A, neochinulin A and B, and aspulvinone D, M, and R, have potent in vitro anti-SARS-CoV-2 activity, targeting the main protease (M^pro). In the near and distant future, these molecules could be used to develop antiviral drugs for treating infections and preventing the spread of disease.     

Efficiency of Fe3O4 Nanoparticles with Different Pretreatments for Enhancing Biogas Yield of Macroalgae Ulva intestinalis Linnaeus

In this work, different pretreatment methods for algae proved to be very effective in improving cell wall dissociation for biogas production. In this study, the Ulva intestinalis Linnaeus (U. intestinalis) has been exposed to individual pretreatments of (ultrasonic, ozone, microwave, and green synthesized Fe₃O₄) and in a combination of the first three mentioned pretreatments methods with magnetite (Fe₃O₄) NPs, (ultrasonic-Fe₃O₄, ozone-Fe₃O₄ and microwave-Fe₃O₄) in different treatment times. Moreover, the green synthesized Fe₃O₄ NPs has been confirmed by FTIR, TEM, XRD, SEM, EDEX, PSA and BET. The maximum biogas production of 179 and 206 mL/g VS have been attained when U. intestinalis has been treated with ultrasonic only and when combined microwave with Fe₃O₄ respectively, where sediment were used as inoculum in all pretreatments. From the obtained results, green Fe₃O₄ NPs enhanced the microwave (MW) treatment to produce a higher biogas yield (206 mL/g VS) when compared with individual MW (84 mL/g VS). The modified Gompertz model (R² = 0.996 was appropriate model to match the calculated biogas production and could be used more practically to distinguish the kinetics of the anaerobic digestion (AD) period. The assessment of XRD, SEM and FTIR discovered the influence of different treatment techniques on the cell wall structure of U. intestinalis.     

DNA/bovine serum albumin binding and cytotoxicity of transition metal ternary complexes based on sulfamethazine and bromazepam drugs

Similar to the antibiotic mixing strategies, which depend on reducing the worth of diffusion of the resistant bacteria to new host, in this contribution, we explicit new mixed-ligand complexes of the type [M(SMZ)₂(BZM)] (M = Co(II), Ni(II) and Cu(II)) based on two drugs: sulfamethazine (SMZ) and bromazepam (BZM). The novelty aspect of the present work relies on combining two drugs in a single molecule via the synthesis of the ternary complexes. The ternary complexes were characterized by spectroscopic and analytical tools with the aid of the quantum chemical calculations. Copper(II) complex has the highest DNA intrinsic binding constant (2.20 × 10⁵ M⁻¹), induces extensively DNA cleavage compared to the other complexes, and exhibits the highest cytotoxicity (IC₅₀ = 0.67 μM) against human liver cancer cell line (HepG2). Exciting, Cu(II) compound exhibits no toxicity to the nonmalignant human foetal lung fibroblast (WI-38). Alternatively, the low cytotoxicity of the Co(II) complex correlates well with the high affinity of the compound to human serum albumin (K_b = 4.58 × 10⁵) compared to 1.93 × 10⁵ and 2.14 × 10⁵ M⁻¹ for Ni (II) and Cu (II) complexes, respectively.     

Mineralized Polyvinyl Alcohol/Sodium Alginate Hydrogels Incorporating Cellulose Nanofibrils for Bone and Wound Healing

Bio sustainable hydrogels including tunable morphological and/or chemical cues currently offer a valid strategy of designing innovative systems to enhance healing/regeneration processes of damaged tissue areas. In this work, TEMPO-oxidized cellulose nanofibrils (T-CNFs) were embedded in alginate (Alg) and polyvinyl alcohol (PVA) solution to form a stable mineralized hydrogel. A calcium chloride reaction was optimized to trigger a crosslinking reaction of polymer chains and mutually promote in situ mineralization of calcium phosphates. FTIR, XRD, SEM/EDAX, and TEM were assessed to investigate the morphological, chemical, and physical properties of different mineralized hybrid hydrogels, confirming differences in the deposited crystalline nanostructures, i.e., dicalcium phosphate dehydrate (DCPDH) and hydroxyapatite, respectively, as a function of applied pH conditions (i.e., pH 4 or 8). Moreover, in vitro tests, in the presence of HFB-4 and HSF skin cells, confirmed a low cytotoxicity of the mineralized hybrid hydrogels, and also highlighted a significant increase in cell viability via MTT tests, preferentially, for the low concentration, crosslinked Alg/PVA/calcium phosphate hybrid materials (<1 mg/mL) in the presence of hydroxyapatite. These preliminary results suggest a promising use of mineralized hybrid hydrogels based on Alg/PVA/T-CNFs for bone and wound healing applications.     

Linear relations betweenE-functions and Bessel functions

In this paper, some new linear relations for MacRobert'sE-Functions are established. They are formulae (1), (10), (15), (20), (22) and (28) below. For the definitions and properties of these functions, the reader is referred to MacRobert, “Functions of a Complex Variable” (3rd ed., London 1946), p. 348. This work will be denoted by the letters C.V. Also some expansions of Bessel Functions are deduced.     

Effect of flow on quasi-one-dimensional acoustic wave propagation in a variable area duct of finite length

The general equation for the velocity potential of quasi-one-dimensional acoustic wave motion in a variable area, finite duct with one-dimensional flow is derived by using a perturbation technique. The non-linear second-order partial differential equation is linearized and then solved, by either a power series expansion method or the Runge-Kutta fourth-order method, for harmonic time dependence. The boundary condition taken at the duct mouth is that of matching the impedance of the duct sound field to that of the radiation field at the duct opening. Three axial Mach number variations along the duct axis are considered and the results obtained are compared with those for the case of constant Mach number, to determine the influence of the axial velocity gradient on sound propagation. The effect of flow on the radiation impedance is also considered.     

Spectroscopic investigations and electrical properties of PVA/PVP blend filled with different concentrations of nickel chloride

Films of PVA/PVP blend (50/50) filled with different concentrations of NiCl₂ were prepared by casting method. The prepared films were investigated by different techniques. XRD scans demonstrated that the peak intensity at 2θ≈20° decreased and the band width increased with increase in the concentrations of NiCl₂ content, which implied decrease in the degree of crystallization and hence causes increase in the amorphous region. UV-vis analysis revealed that the values of the optical band gap are affected with increase in NiCl₂ content. This indicates the formation of charge transfer complexes between the polymer blend and the filler. The rise of conductivity is significant with increased concentration of NiCl₂ filler; this reveals an increase in degree of amorphosity. AC conductivity (σ_ac) behavior of all the prepared films was investigated over the frequency range 42 Hz-5 MHz and under different isothermal stabilization in the temperature range 313-393 K. It suggests that the hopping mechanism might be playing an important role in the conduction process in high frequency region. The dielectric behavior was analyzed using dielectric permittivity (ε´, ε″) dielectric loss tangent (tan δ) and electric modulus (M″). The decrease in dielectric permittivity was observed with increase in the concentration of NiCl₂ filler. This suggests the role of NiCl₂ as filler to improve the electrical conductivity of PVA/PVP blend.     

Bestimmung des gerichteten spektralen Emissionsgrades von Feststoffen im Wellenlängenbereich von 2,5 µm bis 45 µm bei Temperaturen zwischen 80°C und 350°C

Zusammenfassung Der beschriebene Meßaufbau gestattet, den gerichteten spektralen Emissionsgrad im Wellenlängenbereich von 2,5 µm bis 45 µm bei Temperaturen zwischen 80°C und 400°C zu bestimmen. Die Proben müssen für Strahlung der untersuchten Wellenlänge undurchlässig sein und einen Durchmesser zwischen 50 mm und 90 mm bei einer Dicke bis zu 10 mm haben. Die Standardabweichung bei der Bestimmung des spektralen Emissionsgrades beträgt 1,0%. Zur Bestimmung des spektralen Emissionsgrades werden die spektralen Strahldichten des Schwarzen Körpers und der Probenoberfläche bei bekannter Temperatur mit einem Fourierspektrometer verglichen. Die problematische Bestimmung der Probenoberflächentemperatur geschieht mittels der Fourierschen Wärmeleitungsgleichung mit der bekannten, gesondert zu bestimmenden Wärmeleitfähigkeit der Probe und dem berechneten Energieverlust der Oberfläche an die Umgebung durch Leitung, Konvektion und Strahlung. Zur Überprüfung der Meßergebnisse wurde der senkrechte spektrale Emissionsgrad an drei beschichteten Glasproben gemessen, an denen bei einem internationalen Vergleich der Gesamtemissionsgrad gemessen wurde. Die aus den hier bestimmten spektralen Werten berechneten senkrechten Gesamtemissionsgrade zeigten eine sehr hohe Übereinstimmung mit den Werten aus dem internationalen Vergleich und anderen Meßwerten.

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Determination of the directional spectral emissivity of solids in the spectral range from 2.5 µm to 45 µm at temperatures between 80°C and 350°C

The measuring set-up described allows the directional spectral emissivity to be determined in the wavelength range from 2.5 ¶m to 45 ¶m at temperatures between 80°C and 400°C. The samples must be opaque to radiation of the wavelength investigated. They must have a diameter of between 50 mm and 90 mm and be up to 10 mm thick. The uncertainty of the determination of the spectral emissivity amounts to 1.0%. To determine the spectral emissivity, the spectral radiances of black-body and sample surface are compared at known temperature using a Fourier spectrometer. The problematic determination of the sample surface temperature is carried out on the basis of Fourier's equation of thermal conduction, making use of the known thermal conductivity of the sample (which must be separately determined) and the calculated energy loss from the surface to the environment by conduction, convection and radiation. To check the measurement results, the vertical spectral emissivity was measured on three coated glass samples whose total emissivity had been measured in an international comparison. The total vertical emissivities calculated from the spectral values determined here show very good agreement with the values obtained in the international comparison and with other measurement values.