Stigmatellamines A–D: Bacterial Membrane Vesicle-Induced N‑Alkylpyridinium Alkaloids from Stigmatella aurantiaca

Four N-alkylpyridinium alkaloids, stigmatellamines A–D (1–4), were isolated from Stigmatella aurantiaca as metabolites induced by membrane vesicles derived from Burkholderia plantarii. Their chemical structures were elucidated through a combination of spectroscopic and synthetic approaches, revealing a unique class of tetrasubstituted N-alkylpyridinium alkaloids. Stigmatellamines A–C exhibited potent cytotoxicity against the human B-cell lymphocytes, RPMI8226. This is the first evidence supporting the ability of B. plantarii MVs to induce cryptic metabolite biosynthesis.