The SARS CoV-2 pandemic has affected millions of people around the globe. Despite many efforts to find some effective medicines against SARS CoV-2, no established therapeutics are available yet. The use of phytochemicals as antiviral agents provides hope against the proliferation of SARS-CoV-2. Several natural compounds were analyzed by virtual screening against six SARS CoV-2 protein targets using molecular docking simulations in the present study. More than a hundred plant-derived secondary metabolites have been docked, including alkaloids, flavonoids, coumarins, and steroids. SARS CoV-2 protein targets include Main protease (M^Pro), Papain-like protease (PL^pro), RNA-dependent RNA polymerase (RdRp), Spike glycoprotein (S), Helicase (Nsp13), and E-Channel protein. Phytochemicals were evaluated by molecular docking, and MD simulations were performed using the YASARA structure using a modified genetic algorithm and AMBER03 force field. Binding energies and dissociation constants allowed the identification of potentially active compounds. Ligand-protein interactions provide an insight into the mechanism and potential of identified compounds. Glycyrrhizin and its metabolite 18-β-glycyrrhetinic acid have shown a strong binding affinity for M^Pro, helicase, RdRp, spike, and E-channel proteins, while a flavonoid Baicalin also strongly binds against PL^pro and RdRp. The use of identified phytochemicals may help to speed up the drug development and provide natural protection against SARS-CoV-2.

Streptococcus thermophilus is used primarily as starter cultures to counter the harmful bacteria grown in cheese and yogurt making/preservation processes. These bacteria produce some exogenous toxins called bacteriocins having the antimicrobial activities against both Gram positive and Gram negative bacteria. In our study S. thermophilus growth was obtained at pH 5.5 and temperature 40°C. Bacteriocin activities were checked after their treatment with different enzymes, organic solvents, sodium chloride (NaCl) and detergents as well as their heat stability and effect of pH was studied. Bacteriocin activity was found heat stable at 100°C for 30 min and was found stable in the 3-10 pH range but lost the activity after the treatment with proteinase-K and protease enzymes. Activity was lost in treatment with lipase and amylase which shows the presence of lipo-glycolated peptide. Bacteriocin activity was lost on the presence of Dithiothreitol (DTT) and b-mercaptoethanol which showed the presence of disulphide bond present in bacteriocin and essential for its activity. Urea and ethylene diamine tetraacetic acid (EDTA) also affected the bacteriocin activity but found stable to survive in the presence of 6% NaCl. Antibacterial assay showed the strong growth inhibition of test bacteria. Bactericidal activity was further purified to homogeneity by ammonium sulphate precipitation and different chromatographic techniques. Molecular weight was calculated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) as 2.7 kDa. Key words: Streptococcus thermophilus, bacteriocin, antimicrobial peptide, yogurt culture bacteriocin, disc diffusion test.

Vascular catheter-related infections and thrombosis are common and may lead to serious complications after catheterization. Reducing the incidence of such infections has become a significant challenge. This study aims to develop a super hydrophobic nanocomposite drug-loaded vascular catheter that can effectively resist bacterial infections and blood coagulation. In this study, a SiO₂ nanocoated PTFE (Polytetrafluoroethylene) catheter (PTFE-SiO₂) was prepared and further optimized to prepare a SiO₂ nanocoated PTFE catheter loaded with imipenem/cilastatin sodium (PTFE-IC@dMSNs). The catheters were characterized for performance, cell compatibility, anticoagulant performance, in vitro and in vivo antibacterial effect and biological safety. PTFE-IC@dMSNs catheter has efficient drug loading performance and drug release rate and has good cell compatibility and anticoagulant effect in vitro. Compared with the PTFE-SiO₂ catheter, the inhibition ring of the PTFE-IC@dMSNs catheter against Escherichia coli increased from 3.98 mm² to 4.56 mm², and the antibacterial rate increased from about 50.8 % to 56.9 %, with a significant difference (p < 0.05). The antibacterial zone against Staphylococcus aureus increased from 8.63 mm² to 11.74 mm², and the antibacterial rate increased from approximately 83.5 % to 89.3 %, showing a significant difference (p < 0.05). PTFE-IC@dMSNs catheter also has good biocompatibility in vivo. Furthermore, the PTFE-IC@dMSNs catheter can reduce the adhesion of blood cells and have excellent anticoagulant properties, and even maintain these properties even with the addition of imipenem/cilastatin sodium. Compared with PTFE, PTFE-SiO₂ and PTFE-IC@dMSNs catheters have good characterization performance, cell compatibility, and anticoagulant properties. PTFE SiO₂ and PTFE-IC@dMSNs catheters have good antibacterial performance and tissue safety against E. coli and S. aureus. Relatively, PTFE-SiO₂ and PTFE-IC@dMSNs catheter has better antibacterial properties and histocompatibility and has potential application prospects in anti-bacterial catheter development and anticoagulation.