Schaftoside inhibits 3CLpro and PLpro of SARS-CoV-2 virus and regulates immune response and inflammation of host cells for the treatment of COVID-19.

It is an urgent demand worldwide to control the coronavirus disease 2019 (COVID-19) pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus. The 3-chymotrypsin-like protease (3CLpro) and papain-like protease (PLpro) are key targets to discover SARS-CoV-2 inhibitors. After screening 12 Chinese herbal medicines and 125 compounds from licorice, we found that a popular natural product schaftoside inhibited 3CLpro and PLpro with IC50 values of 1.73 ± 0.22 and 3.91 ± 0.19 µmol/L, respectively, and inhibited SARS-CoV-2 virus in Vero E6 cells with EC50 of 11.83 ± 3.23 µmol/L. Hydrogen-deuterium exchange mass spectrometry analysis, quantum mechanics/molecular mechanics calculations, together with site-directed mutagenesis indicated the antiviral activities of schaftoside were related with non-covalent interactions with H41, G143 and R188 of 3CLpro, and K157, E167 and A246 of PLpro. Moreover, proteomics analysis and cytokine assay revealed that schaftoside also regulated immune response and inflammation of the host cells. The anti-inflammatory activities of schaftoside were confirmed on lipopolysaccharide-induced acute lung injury mice. Schaftoside showed good safety and pharmacokinetic property, and could be a promising drug candidate for the prevention and treatment of COVID-19.

NMR studies of daidzein and puerarin: active anti-oxidants in traditional Chinese medicine.

Radix puerariae-a popular traditional Chinese medicine-is used for the treatment of diarrhea, acute dysentery, deafness, and cardiovascular diseases. It can also be used as an effective antioxidant and has been tested as an anticancer drug. Daidzein and puerarin are its main active compounds. The present contribution was focused on experimental and theoretical studies of the 1H and 13C NMR chemical shifts and nuclear magnetic shielding parameters of daidzein and puerarin. Experimental data were gained by exploring standard one-dimensional spectra and a set of two-dimensional measurements: COSY, HSQC, and HMBC. The theoretical gauge independent atomic orbital density functional theory supporting studies, were performed to determine shielding constants and chemical shifts in vacuum and methanol-d4 solvent. The correlation between experimental and theoretical data was fairly good, especially when the DFT/PBE0 approach was used. The molecular properties of daidzein and puerine related to antiradical activity were studied in the context of a single-step hydrogen atom transfer mechanism and its correlation with 13C NMR chemical shifts. Graphical abstract Electron spin density distribution for daidzein radical.

Theoretical studies on the mechanism of C-P bond cleavage of a model alpha-aminophosphonate in acidic condition.

Various reaction paths of the P-C bond cleavage of alpha-aminophosphonates in acidic media, resulting in the derivatives of phosphonic acid, has been investigated using density functional level of theories in the gas phase as well as in aqueous medium. Dimethyl (alpha-anilinobenzyl)phosphonate has been used as the model molecule and our investigation confirms a three steps process including protonation, P-C bond cleavage, and the transformation of the products from the final transition state (imine cation and H-phosphonate) through hydrolysis. The most favorable reaction path starts from the amino group protonation, followed by a proton transfer through N-H...O(P) hydrogen bond, and the P-C bond cleavage from the resulting protonated structure. Explicit inclusion of water molecules indicated that two waters are needed for the P-C bond cleavage, and the calculated mechanistic paths in this hydrated model are similar to those of the aqueous solvation model.