Extracts of Sesbania drummondii (Rydb.) Cory seed are active in vivo in the P-388 lymphocytic leukemia system and cytotoxic in the KB assay. Syste- matic fractionation of S. drummondii has yielded sesbanine (1), a novel alkaloid based on the 2,7-naphthyridine nucleus, and drummondol (2), a neswpiraobcsyccisliicc acid (5) metabolite. Sesbanine and drummondol are present in highly cytotoxic fractions; however, these purified compounds are essentially devoid of antitumor activity. © 1981, American Chemical Society. All rights reserved.