(+)-2-N-Methyltelobine [1], a new alkaloid, together with twelve known bisbenzylisoquinolines, was isolated from the tubers of Stephania erecta. The structure determination and the complete 1H- and unambiguous 13C-nmr assignments of 1 were obtained through extensive use of several 1D and 2D nmr techniques. All alkaloids inhibited the growth of cultured Plasmodium falciparum strains D-6 and W-2 and displayed nonselective cytotoxicity with a battery of cultured mammalian cells. These data were used for the calculation of selectivity indices. Relative to known antimalarial agents, these bisbenzylisoquinoline alkaloids do not appear to be promising clinical candidates at the present time.

From the bulbs of Crinum amabile (Amaryllidaceae), a new alkaloid (-)-amabiline [1], together with the known alkaloids (-)-lycorine [2], (-)-buphanisine [3], (-)-augustine [4], and (+)-crinamine [5], were isolated. The structural characterization of 1 and the revised 1H- and 13C-nmr assignments of 2 are discussed. Alkaloids 2, 4, and 5 were found to be the principal cytotoxic and antimalarial constituents.

No abstract

Roots of Nepenthes thorelii yielded plumbagin, 2-methylnaphthazarin, octadecyl caffeate, isoshinanolone, and droserone. In addition, seven derivatives were prepared from plumbagin. Each of these natural and semisynthetic compounds was evaluated for in vitro antimalarial potential.

Biological evaluation of extracts prepared from the tubers of Stephania pierrei revealed cytotoxic and antimalarial activity. During the course of separation, two new aporphine alkaloids, (-)-asimilobine-2-O-beta-D-glucoside [2] and (-)-nordicentrine [8], in addition to twenty-one known isoquinoline alkaloids, were isolated. Each isolate was assessed for cytotoxic and antimalarial activities. It was found that the cytotoxicity of S. pierrei was mainly due to the presence of the aporphine alkaloids containing the 1,2-methylenedioxy group 3-10, whereas the antimalarial activity was attributed to the nonquaternary aporphine alkaloids 1, 3-10 and the tetrahydroprotoberberines possessing a phenolic functionality, 13-15, 18. None of the isolates showed a degree of selectivity comparable to that of antimalarial drugs such as chloroquine, quinine, mefloquine, and artemisinin. Comparison of the alkaloid content of S. pierrei and Stephania erecta strongly suggested separate identities for the two plants.

No abstract

Three xanthone derivatives, gambogic acid, isogambogic acid and isomorellinol, were isolated from the dried latex of Gurcinia hunburyi. Two of them, isogambogic acid and isomorellinol, are new. Determinations of the structures and stereochernistry were achieved independently by a series of NMR experiments including COSY, ROESY, HMQC, HMBC and selective INEPT. Isolation of isomorellinol from G. hnburyi provided important chemical evidence to link this species to G. morella. The presence of gambogic acid and isogambogic acid, however, demonstrated the difference between these two species. Cytotoxic evaluation of these isoiates revealed that al1 three were active against KB and drug-resistant K B V l cell lines.

No abstract