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.