Nigellidine-4-O-sulfite, the First Sulfated Indazole-Type Alkaloid from the Seeds of Nigella sativa

The rare indazole-type alkaloid nigellidine (2) is accompanied by its 4-O-sulfite (4) in the seeds of Nigella sativa. Compound 4 may represent the true natural product leading to nigellidine (2) via hydrolysis of the sulfate functionality during the isolation process. The structure of nigellidine-4-O-sulfite (4) is confirmed by NMR, MS, and X-ray crystallographic data. This is the first report of the natural occurrence of sulfated indazole-type alkaloids.