(Equation presented) Four new dolabellane-type diterpene alkaloids, nigellamines A1 (1), A2 (2), B1 (3), and B 2 (4), were isolated from the seeds of Nigella sativa. Their absolute stereostructures were determined on the basis of chemical and physicochemical evidence. Nigellamines A1 (1), B1 (3), and B2 (4) were found to show potent lipid metabolism promoting activity in primary cultured mouse hepatocytes, and their activities were equivalent to that of a PPAR-α agonist, clofibrate.