An investigation of the Guyana plant Simarouba amara Aubl. (Simaroubaceae) for antineoplastic quassinoids led to isolation and structural determination of the new quassinoids 2'-acetylglaucarubine (1a) and 13,18-dehydroglaucarubinone (2). The previously known 2'-acetylglaucarubinone (3a) and glaucarubinone (3b) were also obtained. The new quassinoid 2 was found significantly to inhibit growth of the murine lymphocytic leukemia P388.

Further examination of the hexane extract of the root bark of Simarouba amara (Simaroubaceae) has led to the isolation of two side chain oxygenated Δ7‐tirucallol‐type triterpenes in addition to the already reported compounds 4 and 5. One has been found to be identical with the known melianone 8 and the second is a new compound and has been shown to be 21,20‐anhydromelianone 11. The 13C‐NMR spectra of nine Δ7‐tirucallol derivatives have been analysed and the data obtained have been applied to the confirmation of the structure of the new substance 11.