Isolation and antibacterial activity of three new flavonol compounds from Sophora flavescens

Three new flavonol compounds—kushenmin Q (1), kushenmin R (2), and kushenmin S (3)—along with two known compounds, 2S-sophoflavonoid B (4) and kushenol G (5), were isolated from the ethanol extract of Sophora flavescens root bark. Their structures were elucidated using UV spectroscopy, high-resolution electrospray ionisation mass spectrometry (HRESIMS), nuclear magnetic resonance (NMR), and comparison with published data. The antibacterial activity of compounds 1–5 was evaluated against eight bacterial strains (four Gram-positive and four Gram-negative) using the microbroth dilution method. Among the isolated compounds, the flavones 1, 3, and 4 exhibited significant antibacterial activity, with particularly strong effects against Gram-positive bacteria.