Antiviral Matrine-Type Alkaloids from the Rhizomes of Sophora tonkinensis

Three new matrine-type alkaloids, (+)-5 alpha-hydroxyoxysophocarpine (1), (-)-12 beta-hydroxyoxy-sophocarpine (2), and (+)-5 alpha-hydroxylemannine (3), along with 14 known analogues, (-)-sophocarpine (4), (-)-5 alpha-hydroxysophocarpine (5), (-)-9 alpha-hydroxysophocarpine (6), (+)-12 alpha-hydroxysophocarpine (7), (-)-12 beta-hydroxysophocarpine (8), (+)-oxysophocarpine (9), (+)-matrine (10), (+)-s ophoran ol (11), (+)-9 alpha-hydroxyrnatrine (12), (-)-14 beta-hydroxymatrine (13), (+)-oxymatrine (14), (+)-5 alpha-hydroxyoxymatrine (15), (-)-14 beta-hydroxyoxymatrine (16), and (+)-sophoramine (17), were isolated from the rhizomes of Sophora tonkinensis. Their structures were elucidated via spectrometric data analyses, and the absolute configurations were established by single-crystal X-ray diffraction and ECD data. Alkaloids 2, 6, 11, and 13 exhibited antiviral activity against the Coxsackie virus B3 (CVB3), with IC50 values of 26.62-252.18 mu M, and alkaloids 7, 8, and 17 inhibited influenza virus A/Hanfang/359/95 (H3N2) replication with IC50 values of 63.07-242.46 mu M.