In Silico Evaluation of Natural Flavonoids as a Potential Inhibitor of Coronavirus Disease

The recent coronavirus disease (COVID-19) outbreak in Wuhan, China, has led to millions of infections and the death of approximately one million people. No targeted therapeutics are currently available, and only a few efficient treatment options are accessible. Many researchers are investigating active compounds from natural plant sources that may inhibit COVID-19 proliferation. Flavonoids are generally present in our diet, as well as traditional medicines and are effective against various diseases. Thus, here, we reviewed the potential of flavonoids against crucial proteins involved in the coronavirus infectious cycle. The fundamentals of coronaviruses, the structures of SARS-CoV-2, and the mechanism of its entry into the host’s body have also been discussed. In silico studies have been successfully employed to study the interaction of flavonoids against COVID-19 M^pro, spike protein PL^pro, and other interactive sites for its possible inhibition. Recent studies showed that many flavonoids such as hesperidin, amentoflavone, rutin, diosmin, apiin, and many other flavonoids have a higher affinity with M^pro and lower binding energy than currently used drugs such as hydroxylchloroquine, nelfinavir, ritonavir, and lopinavir. Thus, these compounds can be developed as specific therapeutic agents against COVID-19, but need further in vitro and in vivo studies to validate these compounds and pave the way for drug discovery.     

Valorization of Wild-Type Cannabis indica by Supercritical CO2 Extraction and Insights into the Utilization of Raffinate Biomass

Supercritical CO₂ extraction (SCCO₂) extraction of cannabis oil from Indian cannabis (Cannabis indica) leaves was optimized through a central composite design using CO₂ pressure (150–250 bar), temperature (30–50 °C) and time (1–2 h). From the regression model, the optimal CO₂ pressure, extraction temperature and time were 250 bar, 43 °C and 1.7 h, respectively resulting in the experimental yield of 4.9 wt% of cannabis oil via SCCO₂ extraction. The extract contained cannabidiol, tetrahydrocannabivarin, Δ⁹-tetrahydrocannabinol and Δ⁸-tetrahydrocannabinol as well as two terpenoids such as cis-caryophyllene and α-humulene. Besides SCCO₂ extraction of cannabis oil, the raffinate biomass was utilized to extract polyphenols using water as the extraction medium. Cannabis oil and water extractive were investigated for their half-maximal inhibitory concentration (IC₅₀) values, which were found to be 1.3 and 0.6 mg/mL, respectively. This is comparable to the commercially available antioxidant such as butylated hydroxytoluene with an IC₅₀ value of 0.5 mg/mL. This work on SCCO₂ extraction of cannabinoids and other valuable bioactive compounds provides an environmentally sustainable technique to valorize cannabis leaves.     

Dithiobissuccinimidyl propionate self assembled monolayer based cholesterol biosensor

A dithiobissuccinimidyl propionate (DTSP) self-assembled monolayer (SAM) prepared onto a gold (Au) surface has been utilized for covalent immobilization of cholesterol oxidase (ChOx) and cholesterol esterase (ChEt). These ChOx-ChEt/DTSP/Au bio-electrodes have been characterized using electrochemical impedance and cyclic voltammetric (CV) techniques, respectively. Differential pulse voltammetry (DPV) has been used for enzymatic assay of immobilized ChOx and ChEt onto the DTSP modified gold surface as a function of cholesterol oleate concentration. The response measurement conducted on ChOx-ChEt/DTSP/Au bio-electrode reveal the value of Michaelis-Menten constant (Km) as 0.95 mM suggesting enhanced affinity of enzymes (ChOx and ChEt). The ChOx-ChEt/DTSP/Au bio-electrodes show linearity in range of 50 to 400 mg dl(-1) of cholesterol oleate and the shelf-life of more than 50 days when stored at 4 degrees C. This biosensing electrode shows correlation coefficient of 0.9973 and standard deviation of regression as 0.859 microA.     

Positronium annihilation studies of polycarbonate,polyethersulphone and polysulphone

Positron annihilation studies are reported on polycarbonate polyethersulphone and polysulphone over the temperature range 260–370 K. The data were analysed into three components, the longest lifetime-o-component is associated with the pick-off mechanism; a linear variation of that component with temperature was observed. Using ultrasonic velocity data, the free volume distribution was calculated; its magnitude and temperature dependence are discussed in relation to the mechanical properties of the polymer.     

Fabrication of hollow SiO2 and Au (core)–SiO2 (shell) nanostructures of different shapes by CdS template dissolution

Core–shell silica (SiO₂) coated CdS nanorods (NR) and nanospheres (NS) were prepared (SiO₂@CdS) by deposition of a Si–O–Si amorphous layer over the CdS surface through the hydrolysis of 3-mercaptopropyltrimethoxysilane and tetraethylorthosilicate. Nanoporous SiO₂ matrix (NPSM), hollow SiO₂ nanotubes (HSNT) and nanospheres (HSNS) useful for efficient adsorption and catalytic processes were prepared by chemical dissolution of CdS–NS (size: 9–10 nm) and CdS–NR (length: 116–128 nm and width: 6–11 nm) template from SiO₂@CdS with 2 M HNO₃. These SiO₂ nanostructures were characterized by optical absorption, TEM, EDX, SAED and BET surface area analysis. TEM images revealed the fabrication of slightly distorted HSNS (size: 9–12 nm) and closed HSNT (length: 30–45 nm and diameter: 9–14 nm) of shorter dimensions than the CdS–NR template used. The BET surface area (112–134 m² g^?1) of NPSM and HSNS is found to be larger than the surface area (29–51 m² g^?1) of SiO₂@CdS composites indicating hollow SiO₂ morphology. Silica coated Au (SiO₂@Au) composites formed by CdS dissolution from Au (2 wt%) deposited CdS–NR core-encapsulated into SiO₂ shell (SiO₂@Au–CdS–NR) exhibited a surface plasmon band at 550 nm and displayed high catalytic activity for 4-nitrophenol reduction by Au nanoparticle.     

Effect of thermal annealing on optical properties of CR-39 polymeric track detector

The samples of CR-39 polymer (TASTRAK, Bristol, England) were annealled thermally at various temperatures ranging from 100°C to 180°C for 1 hour, in air. FTIR spectroscopy reveals the structural degradation of CR-39 polymer due to thermal annealing above its glass transition temperature. Optical band gap of pristine and thermally annealed samples has been determined using UV-Visible absorption spectra. It has been observed that the optical band gap decreases continuously as a result of annealing.      

A non-enzymatic sensor for hydrogen peroxide based on polyaniline, multiwalled carbon nanotubes and gold nanoparticles modified Au electrode

We describe the construction of a polyaniline (PANI), multiwalled carbon nanotubes (MWCNTs) and gold nanoparticles (AuNPs) modified Au electrode for determination of hydrogen peroxide without using peroxidase (HRP). The AuNPs/MWCNT/PANI composite film deposited on Au electrode was characterized by Scanning Electron Microscopy (SEM) and electrochemical methods. Cyclic voltammetric (CV) studies of the electrode at different stages of construction demonstrated that the modified electrode had enhanced electrochemical oxidation of H(2)O(2), which offers a number of attractive features to develop amperometric sensors based on split of H(2)O(2). The amperometric response to H(2)O(2) showed a linear relationship in the range from 3.0 μM to 600.0 μM with a detection limit of 0.3 μM (S/N = 3) and with high sensitivity of 3.3 mA μM(-1). The sensor gave accurate and satisfactory results, when employed for determination of H(2)O(2) in milk and urine.     

Transfer Hydrogenation(TH) of Carbonyl Compounds Catalytically Promoted by Pd17Se15 Nanoparticles and PdP2 Nanoflowers

Nanosized Pd₁₇Se₁₅ and PdP₂ were synthesized at moderate temperature (using less toxic TOPO in case of PdP₂) and explored for the first time to catalyze transfer hydrogenation (TH) of aldehydes / ketones using 2-propanol as a source of hydrogen. The optimum catalyst loading was equivalent to 1.0 mol % of Pd. The round shaped Pd₁₇Se₁₅ NPs (15 to 30 nm), resulted on reacting (3-(phenylseleno)propylamine) with Na₂PdCl₄ in a mixture (1 : 1) of olylamine and 1-octadecene at 250 °C for 50 min. Nanoflowers of PdP₂ (25 to 55 nm) were obtained by reacting Na₂PdCl₄ with trioctylphosphine oxide (TOPO) in a similar solvent mixture at 350 °C for 60 min. Both the NPs were found air insensitive and authenticated with powder X-ray diffraction, HR-TEM, SEM, SEM-EDX and XPS. The conversion was found more efficient for aldehydes in comparison to that of ketones. In comparison to most of the other Pd based nano-phases, reported earlier, the present NPs are somewhat better activators for TH.