New Glucosinolates and Alkaloids with Antibacterial Activities from Raphani Semen

Sixteen compounds were isolated from Raphani Semen, including nine new glucosinolate compounds, raseglucosinolate A–I (1–9), four new alkaloids, rasemenine A–D (10–13), two known 4-methylthio-butyl derivatives (14, 15), and one known alkaloid (16). Compounds 1–13 were structurally characterized through a combination of HRESIMS, NMR, UV, IR, and ECD analyses. The potential antibacterial activities of selected compounds were evaluated. Compounds 3 and 10 exhibited inhibitory effects against Escherichia coli, with MIC of 32 and 64 μg/mL, respectively. Further mechanistic investigations demonstrated that 3 exerts its antibacterial activity by compromising the integrity of the cell wall and membrane, resulting in the leakage of intracellular contents and subsequent disruption of cellular metabolism and growth. Molecular docking analysis suggested that DNA gyrase and topoisomerase IV may be potential molecular targets of 3. Moreover, the combination of 3 with ampicillin sodium exhibited an additive antibacterial effect. These studies suggest that 3 has the potential to become an antibacterial agent and an antibiotic adjuvant.