Euchrestifolines A-O, fifteen novel carbazole alkaloids with potent anti-ferroptotic activity from Murraya euchrestifolia

Fifteen novel carbazole alkaloids, euchrestifolines A-O (1-15), were obtained from Murraya euchrestifolia. Their structures were elucidated by spectroscopic analysis, Mosher's ester, calculated ECD, and transition metal complex ECD methods. Notably, euchrestifolines A-C (1-3) are the first naturally occurring pyrrolidone carbazoles to be identified, while euchrestifolines D-F (4-6) represent rare carbazole alkaloids containing a phenylpropanyl moiety; euchrestifoline G (7) features a unique benzopyranocarbazole skeleton. More importantly, these compounds exhibited significant anti-ferroptotic activity, along with inhibitory effects of nitric oxide (NO) production and notable cytotoxicity. This study marks the first disclosure of carbazole's inhibitory effects against ferroptosis, and the EC₅₀ values of some carbazoles ranging from 0.04 to 1 μM, substantially lower than the positive control, ferrostatin-1. In sum, this research not only enhances our understanding of carbazole alkaloids but also opens new avenues for the discovery of ferroptosis-related leading compounds.