Bioactivity-guided isolation of compounds from <i>Sophora flavescens</i> with antibacterial activity against <i>Acinetobacter baumannii</i>

Abstract

Bioactivity-guided fraction of an extract of <i>Sophora flavescens</i> to identify antibacterial compounds against <i>Acinetobacter baumannii</i>, led to the isolation of two new compounds, (2″<i>R</i>)-5-methoxy-7-hydroxy-8-lavandulylchromone (13) and (2<i>S</i>,<i>βS</i>)-(-)-sophobiflavonoid CE (19), and 18 known flavonoids, (6a<i>R</i>,11a<i>R</i>)-(-)-maackiain (1), (2<i>S</i>)-(-)-8-prenylnaringenin (2), (2<i>S</i>)-(-)-exiguaflavanone K (3), (2<i>S</i>)-(-)-sophoraflavanone G (4), (2<i>S</i>)-(-)-leachianone A (5), (2<i>S</i>)-(-)-kushenol E (6), (2<i>S</i>)-(-)-leachianone G (7), (±)-kushenol F (8), (2<i>S</i>)-(-)-kurarinone (9), (2<i>S</i>)-(-)-kurarinol (10), (2 <i>R</i>,3<i>R</i>)- (+)-3,7,4'-trihydroxy-5-methoxy-8-prenylflavanone (11), (2<i>S</i>)-(-)-isoxanthohumol (12), (2<i>S</i>)-(-)-2'-methoxykurarinone (14), (2 <i>R</i>,3<i>R</i>)-(+)-kushenol I (15), calycosin (16), kuraridin (17), (2<i>S</i>)-(-)-kushenol A (18), and trifolirhizin (20). Their structures were elucidated based on NMR, MS, and CD spectroscopic analysis. Among them, <b>1</b>, <b>2</b>, <b>5</b>, and <b>15</b> exerted modest antibacterial activity against <i>A. baumannii</i>, with MIC₉₅ of 128-256 μg/mL for <b>2</b> and 256-512 μg/mL for <b>1</b>, <b>5</b> and <b>15</b>.