HPLC quantification of fourteen flavonoids in Sophora flavescens Aiton extracts and component-effect relationship against Acinetobacter baumannii

Sophora flavescens Aiton is a traditional Chinese medicine for clearing heat and dampness. 80% ethanol extracts from 13 batches of this herb displayed 2.42%–82.88% inhibition at 512 μg/mL against Acinetobacter baumannii, a bacterium that cause a variety of healthcare-associated infections. In this study, a new HPLC-DAD method was developed for simultaneous quantification of 14 flavonoids, and an orthogonal signal correction assisted partial least squares regression chemometric method was firstly applied to analyse component-effect relationship of extracts against A. baumannii. Five major flavonoids, viz. trifolirhizin (20) (0.81%–3.37%), sophoraflavanone G (4) (0.77%–6.01%), kushenol N (22) (0.23%–2.31%), kurarinone (9) (1.84%–7.29%) and isoxanthohumol (12) (0.06%–1.41%), with variable importance projection values exceeding 1, were found to play important roles. Among them, 9 and 22 were negatively correlated with extract’s antibacterial activity, whereas 4, 12 and 20 were positively correlated. These flavonoids may be regarded as biomarkers of S. flavescens extracts against A. baumannii.