A new isoquinoline alkaloid, nigellimine 111, has been isolated as a trace constituent from the seeds of Nigella sativa. The structure was assigned on the basis of chemical and spectroscopic studies. Nigella sativa L. (Ranunculaceae) is an herbaceous plant that grows in Mediterranean countries and is also cultivated in Pakistan. The seeds are used as a spice and medicine (1,2). Little work has previously been carried out on its alkaloidal constituents (3-5). As a result of our continuing chemical analysis of the seeds (6,7), we report here the isolation, structure determination, and synthesis of a new isoquinoline alkaloid, nigellimine 111. The structure of nigellimine as 1 methyl-6,7-dimethoxyisoquinoline was confirmed by its synthesis and direct comparison with the synthetic compound (9), as well as by its conversion to nigellimine N-oxide which has been earlier isolated from the same seeds (7). The compound was synthesized earlier by Brossi et al. (8).