No abstract

Natural products have served human life as medications for centuries. During the outbreak of COVID-19, a number of naturally derived compounds and extracts have been tested or used as potential remedies against COVID-19. Tetradenia riparia extract is one of the plant extracts that have been deployed and claimed to manage and control COVID-19 by some communities in Tanzania and other African countries. The active compounds isolated from T. riparia are known to possess various biological properties including antimalarial and antiviral. However, the underlying mechanism of the active compounds against SARS-CoV-2 remains unknown. Results in the present work have been interpreted from the view point of computational methods including molecular dynamics, free energy methods, and metadynamics to establish the related mechanism of action. Among the constituents of T. riparia studied, luteolin inhibited viral cell entry and was thermodynamically stable. The title compound exhibit residence time and unbinding kinetics of 68.86 ms and 0.014 /ms, respectively. The findings suggest that luteolin could be potent blocker of SARS-CoV-2 cell entry. The study shades lights towards identification of bioactive constituents from T. riparia against COVID-19, and thus bioassay can be carried out to further validate such observations. Supplementary Information The online version contains supplementary material available at 10.1007/s00894-021-04833-x.

Abstract:The interaction between glucosamine molecules has been studied theoretically. The geometrical structures of monomer (A), dimer (AA) and trimer (AAA) molecules of glucosamine were optimized and vibrational spectra were calculated by DFT/B3LYP method using GAMESS software (Firefly version 8.0.0). The theoretical vibrational spectra for the glucosamine dimer and trimer correspond well to the experimental IR spectrum of chitosan. The energies and enthalpies of association of A to form the dimer and trimer have been determined. The enthalpies of dimerization, A + A = AA + H 2 O, and trimerization, AA + A = AAA + H 2 O, are −48 and −45 kJ/mol, respectively. The thermodynamic functions of the monomer, dimer, and trimer molecules of glucosamine have been calculated.

The outbreak of COVID-19, caused by SARS-COV-2, is responsible for higher mortality and morbidity rates across the globe.

In this work, we have studied the aggregation properties of niclosamide in water by varying the number of monomers.