Dual inhibition of SARS-CoV-2 spike and main protease through a repurposed drug, rutin.

The global health emergency caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led to alarming numbers of fatalities across the world. So far the researchers worldwide have not been able to discover a breakthrough in the form of a potent drug or an effective vaccine. Therefore, it is imperative to discover drugs to curb the ongoing menace. In silico approaches using FDA approved drugs can expedite the drug discovery process by providing leads that can be pursued. In this report, two drug targets, namely the spike protein and main protease, belonging to structural and non-structural class of proteins respectively, were utilized to carry out drug repurposing based screening. The exposed nature of the spike protein on the viral surface along with its instrumental role in host infection and the involvement of main protease in processing of polyproteins along with no human homologue make these proteins attractive drug targets. Interestingly, the screening identified a common high efficiency binding molecule named rutin. Further, molecular dynamics simulations in explicit solvent affirmed the stable and sturdy binding of rutin with these proteins. The decreased Rg value (4 nm for spike-rutin and 2.23 nm for main protease-rutin) and stagnant SASA analysis (485 nm/S2/N in spike-rutin and 152 nm/S2/N in main protease-rutin) for protein surface and its orientation in the exposed and buried regions suggests a strong binding interaction of the drug. Further, cluster analysis and secondary structure analysis of complex trajectories validated the conformational changes due to binding of rutin.

Bacopa monnieri inhibit hen egg white lysozyme fibrillation and help in retaining its activity at acidic condition.

Inhibiting protein misfolding and aggregation is crucial for the treatment of several amyloidoses. Though various types of synthetic drugs are being explored as therapeutic agents, herbal extracts are better alternative owing to their natural origin, higher bioavailability and improved biosafety characteristics. In the present study, we demonstrate that night long (∼12 hr) preincubation of hen egg white lysozyme (HEWL) with Bacopa monnieri (brahmi) at neutral pH, impede the aggregation and fibrillation of protein at pH 2.0. Employing different biophysical techniques such as static and dynamic light scattering, Thioflavin T (ThT) assay, sedimentation assay and atomic force microscopy (AFM), we show that brahmi inhibit the HEWL aggregation in concentration dependent manner. 8-anilino-1-naphthalene sulfonate (ANS) fluorescence reveals that brahmi masks the exposure of hydrophobic domain of lysozyme. Significant recovery of enzymatic activity of HEWL in the presence of brahmi at pH 2.0 is salient feature of this work. Nearly 90% recovery of catalytic activity of lysozyme after 216 hr (9 days) of incubation indicate that interaction of HEWL-brahmi stabilizes the native structure of protein thus enhancing the activation energy barrier for protein misfolding and subsequent aggregation. Our findings show that brahmi could be promising alternative for the therapies of several protein misfolding disorders.Communicated by Ramaswamy H. Sarma.