Flavonoids from the roots and rhizomes of Sophora tonkinensis and their in vitro anti-SARS-CoV-2 activity

Acute respiratory infection caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)had caused a global pandemic since 2019,and posed a serious threat to global health security.Traditional Chinese medicine(TCM)has played an indispensable role in the battle against the epidemic.Many components originated from TCMs were found to inhibit the production of SARS-CoV-23C-like protease(3CLpro)and papain-like protease(PLpro),which are two promising therapeutic targets to inhibit SARS-CoV-2.This study describes a systematic investigation of the roots and rhizomes of Sophora tonkinensis,which results in the characterization of 12 new flavonoids,including seven prenylated flavanones(1−7),one prenylated flavonol(8),two prenylated chalcones(9−10),one isoflavanone(11),and one isoflavan dimer(12),together with 43 known compounds(13−55).Their structures including the absolute configurations were elucidated by comprehensive analysis of MS,1D and 2D NMR data,and time-dependent density functional theory electronic circular dichroism(TDDFT ECD)calculations.Compounds 12 and 51 exhibited inhibitory effects against SARS-CoV-23CLpro with IC_(50) values of 34.89 and 19.88μmol·L^(−1),repectively while compounds 9,43 and 47 exhibited inhibitory effects against PLpro with IC_(50) values of 32.67,79.38,and 16.74μmol·L^(−1),respectively.