Bioactivity-guided isolation of compounds from Sophora flavescens with antibacterial activity against Acinetobacter baumannii

Abstract

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

Graphical Abstract

Keywords:

• Sophora flavescens
• Acinetobacter baumannii
• bioactivity-guided isolation
• flavonoids

Disclosure statement

No potential conflict of interest was reported by the authors.

Supporting information

ESI-MS, UV, CD, 1 D NMR and 2 D NMR data were present in supporting information.

Additional information

Funding

This work was supported by Shandong University, China-Australia Center for Health Sciences Research (2017, 2019), and National Natural Science Foundation of China (81973200).