Novel indole alkaloids from Rauvolfia yunnanensis, inhibiting ESBL producing Escherichia coli by targeting cell membrane integrity

Three unique monoterpenoid indole alkaloids, raufiayunesins A-C (1–3) were obtained from the leaves of Rauvolfia yunnanensis. 1 and 2 were the rare spiro monoterpenoid indole alkaloids structures, that possess a bridged cyclic N, O-ketal spirooxirane core. While 3 with a characterized 11-oxa-13‑azatricyclo [6.4.12,9] tridecane monoterpene part. Their structures were elucidated by the combination of density functional theory (DFT) calculations of the NMR spectra and electronic circular dichroism (ECD) analyses. Compound 1 exhibited significant antibacterial activity against ESBL producing Escherichia coli 330 by damaging the cell membrane integrity.