Extracts of S. drummondii (Rydb.) Cory seed are active in vivo in the [mouse] P-388 lymphocytic leukemia cells system and cytotoxic in the [human oral epidermoid carcinoma] KB cells assay. Systematic fractionation of S. drummondii yielded sesbanine (1), a novel spirocyclic alkaloid based on the 2,7-naphthyridine nucleus, and drummondol (2), a new abscissic acid metabolite. 1 and 2 are present in highly cytotoxic fractions; these purified compounds are essentially devoid of antitumor activity.