Antiviral Matrine-Type Alkaloids from the Rhizomes of <i>Sophora tonkinensis</i>

Three new matrine-type alkaloids, (+)-5α-hydroxyoxy­sophocarpine (1), (−)-12β-hydroxyoxy­sophocarpine (2), and (+)-5α-hydroxylemannine (3), along with 14 known analogues, (−)-sophocarpine (4), (−)-5α-hydroxy­sophocarpine (5), (−)-9α-hydroxy­sophocarpine (6), (+)-12α-hydroxy­sophocarpine (7), (−)-12β-hydroxy­sophocarpine (8), (+)-oxysophocarpine (9), (+)-matrine (10), (+)-sophoranol (11), (+)-9α-hydroxy­matrine (12), (−)-14β-hydroxy­matrine (13), (+)-oxymatrine (14), (+)-5α-hydroxyoxymatrine (15), (−)-14β-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 μM, and alkaloids 7, 8, and 17 inhibited influenza virus A/Hanfang/359/95 (H3N2) replication with IC50 values of 63.07–242.46 μM.