Phycobilins as Potent Food Bioactive Broad-Spectrum Inhibitors Against Proteases of SARS-CoV-2 and Other Coronaviruses: A Preliminary Study

In the 21st century, we have witnessed three coronavirus outbreaks: SARS in 2003, MERS in 2012, and the ongoing pandemic coronavirus disease 2019 (COVID-19). The search for efficient vaccines and development and repurposing of therapeutic drugs are the major approaches in the COVID-19 pandemic research area. There are concerns about the evolution of mutant strains (e.g., VUI – 202012/01, a mutant coronavirus in the United Kingdom), which can potentially reduce the impact of the current vaccine and therapeutic drug development trials. One promising approach to counter the mutant strains is the “development of effective broad-spectrum antiviral drugs” against coronaviruses. This study scientifically investigates potent food bioactive broad-spectrum antiviral compounds by targeting main protease (Mpro) and papain-like protease (PLpro) proteases of coronaviruses (CoVs) using in silico and in vitro approaches. The results reveal that phycocyanobilin (PCB) shows potential inhibitor activity against both proteases. PCB had the best binding affinity to Mpro and PLpro with IC50 values of 71 and 62 μm, respectively. Also, in silico studies with Mpro and PLpro enzymes of other human and animal CoVs indicate broad-spectrum inhibitor activity of the PCB. As with PCB, other phycobilins, such as phycourobilin (PUB), phycoerythrobilin (PEB), and phycoviolobilin (PVB) show similar binding affinity to SARS-CoV-2 Mpro and PLpro

Encapsulation and biocatalytic activity of the enzyme pepsin in fatty lipid films by selective electrostatic interactions

The encapsulation of pepsin by electrostatically controlled diffusion from solution into thermally evaporated fatty amine films is described and the catalytic activity of the immobilized enzyme on hemoglobin is investigated

Synthesis of β-triphosphotriester pronucleotides

Dinucleoside phosphorochloridite were synthesized from phosphorus trichloride and three nucleoside analogues, 3-fluoro-2,3-dideoxythymidine (FLT), 2\u27,3\u27-dideoxy-5-fluoro-3\u27- thiacytidine (FTC), and 2\u27,3\u27-dideoxy-3\u27-thiacytidine (3TC), in a multistep synthesis. Polymerbound N-Boc p-acetoxybenzyl 5¢-O-2¢-deoxythymidine was reacted with dinucleoside phosphorochloridite in the presence of 2,6-lutidine, followed by the reaction with dodecyl alcohol and 5-(ethylthio)-1H-tetrazole, oxidation with tert-butyl hydroperoxide, and acidic cleavage, respectively, to afford the b-triphosphotriester derivatives containing three different nucleosides

Downregulation of APOBEC3G by xenotropic murine leukemia-virus related virus (XMRV) in prostate cancer cells

<p>Abstract</p> <p>Background</p> <p>Xenotropic murine leukemia virus (MLV)-related virus (XMRV) is a gammaretrovirus that was discovered in prostate cancer tissues. Recently, it has been proposed that XMRV is a laboratory contaminant and may have originated via a rare recombination event. Host restriction factor APOBEC3G (A3G) has been reported to severely restrict XMRV replication in human peripheral blood mononuclear cells. Interestingly, XMRV infects and replicates efficiently in prostate cancer cells of epithelial origin. It has been proposed that due to lack off or very low levels of A3G protein XMRV is able to productively replicate in these cells.</p> <p>Findings</p> <p>This report builds on and challenges the published data on the absence of A3G protein in prostate epithelial cells lines. We demonstrate the presence of A3G in prostate epithelial cell lines (LNCaP and DU145) by western blot and mass spectrometry. We believe the discrepancy in A3G detection is may be due to selection and sensitivity of A3G antibodies employed in the prior studies. Our results also indicate that XMRV produced from A3G expressing LNCaP cells can infect and replicate in target cells. Most importantly our data reveal downregulation of A3G in XMRV infected LNCaP and DU145 cells.</p> <p>Conclusions</p> <p>We propose that XMRV replicates efficiently in prostate epithelial cells by downregulating A3G expression. Given that XMRV lacks accessory proteins such as HIV-1 Vif that are known to counteract A3G function in human cells, our data suggest a novel mechanism by which retroviruses can counteract the antiviral effects of A3G proteins.</p

Solid-phase synthesis of 5′-O-β,γ-methylenetriphosphate derivatives of nucleosides and evaluation of their inhibitory activity against HIV-1 reverse transcriptase

Bis(dichlorophosphino)methane was converted to a β,γ-methylenetriphosphitylating reagent. The reagent was immobilized on aminomethyl polystyrene resin-bound linker of 4-acetoxy-3-phenylbenzyl alcohol to afford a polymer-bound β,γ-methylenetriphosphitylating reagent, which was reacted with unprotected nucleosides followed by oxidation with tert-butyl hydroperoxide, deprotection of cyanoethoxy groups with DBU, and acidic cleavage to produce 5′-O-β,γ-methylene triphosphate nucleosides in 53–82% overall yields. Among all the compounds, cytidine 5′-O-β,γ-methylenetriphosphate inhibited completely RNase H activity of HIV-1 reverse transcriptase at 700 μM. [Refer to PDF for graphical abstract

Phycobilins as Potent Food Bioactive Broad-Spectrum Inhibitors Against Proteases of SARS-CoV-2 and Other Coronaviruses: A Preliminary Study

In the 21st century, we have witnessed three coronavirus outbreaks: SARS in 2003, MERS in 2012, and the ongoing pandemic coronavirus disease 2019 (COVID-19). The search for efficient vaccines and development and repurposing of therapeutic drugs are the major approaches in the COVID-19 pandemic research area. There are concerns about the evolution of mutant strains (e.g., VUI – 202012/01, a mutant coronavirus in the United Kingdom), which can potentially reduce the impact of the current vaccine and therapeutic drug development trials. One promising approach to counter the mutant strains is the “development of effective broad-spectrum antiviral drugs” against coronaviruses. This study scientifically investigates potent food bioactive broad-spectrum antiviral compounds by targeting main protease (Mpro) and papain-like protease (PLpro) proteases of coronaviruses (CoVs) using in silico and in vitro approaches. The results reveal that phycocyanobilin (PCB) shows potential inhibitor activity against both proteases. PCB had the best binding affinity to Mpro and PLpro with IC50 values of 71 and 62 μm, respectively. Also, in silico studies with Mpro and PLpro enzymes of other human and animal CoVs indicate broad-spectrum inhibitor activity of the PCB. As with PCB, other phycobilins, such as phycourobilin (PUB), phycoerythrobilin (PEB), and phycoviolobilin (PVB) show similar binding affinity to SARS-CoV-2 Mpro and PLpro

Synthesis and anti-HIV activities of bis-(cycloSaligenyl) pronucleotides derivatives of 3′-fluoro-3′-deoxythymidine and 3′-azido-3′-deoxythymidine

Anti-HIV nucleoside monophosphates have limited cellular uptake due to the presence of negatively-charged phosphate group. Bis-(cycloSaligenyl) derivatives containing two anti-HIV nucleosides, 3′-fluoro-3′-deoxythymidine (FLT) and 3′-azido-3′-deoxythymidine (AZT) were synthesized to increase intracellular delivery of nucleoside monophosphates. 2,5-Bis(hydroxymethylene)benzene-1,4-diol was selected as a monocyclic bidentate scaffold and synthesized by three different methods from bis(hydroxymethylene)cyclohexan-1,4-diene-1,4-diol, or diethyl 2,5-dihydroxyterephthalate. The reaction of the tetraol with diisopropylphosphoramidous dichloride in the presence of 2,6-lutidine, followed by conjugation reactions with nucleosides (i.e., FLT and AZT) and oxidation afforded symmetrical and unsymmetrical bis-(cycloSaligenyl) diphosphate triester products, AZT–AZT, FLT–FLT, and FLT–AZT conjugates, in 63–74% overall yields and modest anti-HIV activities (IC50 = 2.8–69.6 μM). [Refer to PDF for graphical abstract

Synthesis of nucleoside 5′-\u3cem\u3eO\u3c/em\u3e-α,β-methylene-β-triphosphates and evaluation of their potency towards inhibition of HIV-1 reverse transcriptase

A polymer-bound α,β-methylene-β-triphosphitylating reagent was synthesized and subjected to reactions with unprotected nucleosides, followed by oxidation, deprotection of cyanoethoxy groups, and acidic cleavage to afford nucleoside 5′-O-α,β-methylene-β-triphosphates. Among all the compounds, cytidine 5′-O-α,β-methylene-β-triphosphate inhibited RNase H activity of HIV-1 reverse transcriptase with a Ki value of 225 μM

Synthesis of Nucleoside 5′-O-α,β-methylene-β-triphosphates and Evaluation of Their Potency Towards Inhibition of HIV-1 Reverse Transcriptase

A polymer-bound α,β-methylene-β-triphosphitylating reagent was synthesized and subjected to reactions with unprotected nucleosides, followed by oxidation, deprotection of cyanoethoxy groups, and acidic cleavage to afford nucleoside 5′-O-α,β-methylene-β-triphosphates. Among all the compounds, cytidine 5′-O-α,β-methylene-β-triphosphate inhibited RNase H activity of HIV-1 reverse transcriptase with a Ki value of 225 μM