Discovery and characterization of naturally occurring covalent inhibitors of SARS-CoV-2 M^(pro)from the antiviral herb Ephedra

The Chinese herb Ephedra(also known as Mahuang)has been extensively utilized for the prevention and treatment of coronavirus-induced diseases,including coronavirus disease 2019(COVID-19).However,the specific anti-SARS-CoV-2 compounds and mechanisms have not been fully elucidated.The main protease(M^(pro))of SARS-CoV-2 is a highly conserved enzyme responsible for proteolytic processing during the viral life cycle,making it a critical target for the development of antiviral therapies.This study aimed to identify naturally occurring covalent inhibitors of SARS-CoV-2 M^(pro)from Ephedra and to investigate their covalent binding sites.The results demonstrated that the non-alkaloid fraction of Ephedra(ENA)exhibited a potent inhibitory effect against the SARS-CoV-2 M^(pro)effect,whereas the alkaloid fraction did not.Subsequently,the chemical constituents in ENA were identified,and the major constituents'anti-SARS-CoV-2 M^(pro)effects were evaluated.Among the tested constituents,herbacetin(HE)and gallic acid(GA)were found to inhibit SARS-CoV-2 M^(pro)in a time-and dose-dependent manner.Their combination displayed a significant synergistic effect on this key enzyme.Additionally,various techniques,including inhibition kinetic assays,chemoproteomic methods,and molecular dynamics simulations,were employed to further elucidate the synergistic anti-M^(pro)mechanisms of the combination of HE and GA.Overall,this study deciphers the naturally occurring covalent inhibitors of SARS-CoV-2 M^(pro)from Ephedra and characterizes their synergistic anti-M^(pro)synergistic effect,providing robust evidence to support the anti-coronavirus efficacy of Ephedra.

Antibacterial constituents from Melodinus suaveolens

To investigate the non-alkaloidal chemical constituents of the stems and leaves of Melodinus suaveolens and their antibacterial activities. Compounds were isolated and purified by repeated silica gel, Sephadex LH-20, RP18, and preparative HPLC. Their structures were elucidated by comparison with published spectroscopic data, as well as on the basis of extensive spectroscopic analysis. The antibacterial screening assays were performed by the dilution method. Fourteen compounds were isolated, and identified as lycopersene(1), betulinic aldehyde(2), 3β-acetoxy-22,23,24,25,26,27-hexanordammaran-20-one(3), 3a-acetyl-2, 3, 5-trimethyl-7ahydroxy-5-(4,8,12-trimethyl-tridecanyl)-1,3a,5,6,7,7a-hexahydro-4-oxainden-1-one(4), 3β-hydroxy-28-norlup-20(29)-ene-17β-hydroperoxide(5), 3β-hydroxy-28-norlup-20(29)-ene-17α-hydroperoxide(6), β-sitosterol(7), 28-nor-urs-12-ene-3β, 17β-diol(8), α-amyrin(9), ergosta-4,6,8(14),22-tetraen-3-one(10), 3β-hydroxy-urs-11-en-28,13β-olide(11), betulin(12), obtusalin(13), and ursolic acid(14). Among the isolates, compounds 1, 2, 6, 8, 10, and 14 showed potent antibacterial activities against the four bacteria. This is the first report of the antibacterial activity of the constituents of Melodinus suaveolens.