Chem. Pharm. Bull. 51(4) 385—389 (2003)

various biological activities, such as antitumor, antimalarial, antifeedant, insecticidal, antiinflammatory, amoebicidal, and herbicidal effects. We are interested in such biologically active compounds and have isolated many quassinoids from plants, such as Brucea antidysenterica, Picrasma ailanthoides, and Brucea javanica. As part of these studies, we investigated the isolation of quassinoids from Ailanthus altissima SWINGLE (Simaroubaceae). In previous papers, we reported on the isolation and structural elucidation of four new quassinoids, ailantinols A, B, C, and D, and related compounds from the stem bark of A. altissima grown in Japan. Recently, 18 quassinoid glycosides and nine known quassinoids, some of which were isolated from A. altissima, were tested for inhibitory activity against human immunodeficiency virus (HIV) replication in H9 lymphocytic cells. Shinjulactones B and C, and ailantinol A, all of which are quassinoids isolated from A. altissima, showed good antiHIV activities (EC50 values of 28.0, 10.6, and 30.0 mM with a therapeutic index of 10.0, 25.0, and 8.2, respectively). In this paper, we report on the isolation and structural elucidation of three new quassinoids, ailantinol E (1), ailantinol F (2), and ailantinol G (3), from A. altissima grown in Taiwan. The known quassinoids chapparin, amarolide-11-acetate, shinjulactone A, shinjulactone C, shinjulactone H, and shinjulactone L, were also isolated from this plant.