Ground seeds (95.1 g) of Centaurea nigra were Soxhlet-extracted, successively, with nhexane, dichloromethane and MeOH (1.1 L each). The MeOH extract was fractionated on a Sep-Pak C18 (10 g) cartridge eluting with a step gradient: 30, 60, 80 and 100% MeOH in water (200 mL each). Preparative-HPLC purification of the fractions yielded arctiin, matairesinoside, matairesinol, arctigenin, thujaplicatin methyl ether, moschamine, and N-(p-coumaroyl)-serotonin. All these compounds were identified unequivocally by UV, optical rotation, FABMS, and extensive 1D and 2D NMR analysis. The five isolated lignans belong to the dibenzylbutyrolactone group of lignans; this is the first report on the occurrence of thujaplicatin methyl ether in Centaurea. Serotonin-based indole alkaloids like moschamine and N-(p-coumaroyl)-serotonin are not of common occurrence in Centaurea, having been found in only two other species before. Amides arising from serotonin and cinnamic acid or its derivatives have also been observed in a few other species of the family Asteraceae.