Bioassay-guided isolation of Duguetia hadrantha yielded two new 4,5-dioxo-1
-azaaporphinoids, hadranthine A(1) and hadranthine B (2), together with the
known alkaloids imbiline-1 (3), sampangine (4), and 3-methoxysampangine (5
), whose structures were determined primarily from BD-NMR H-1-C-13 HMBC, an
d H-1-N-15 HMBC experiments. This is the first report of the co-occurrence
of the copyrine alkaloids 4 and 5, as well as the first report of either co
pyrine or imbiline type alkaloids from a Duguetia species. Compounds 1, 4,
and 5 demonstrated in vitro antimalarial activity against Plasmodium falcip
arum (W-2 clone), while 2 was inactive. Instead, 2 showed in vitro cytotoxi
city to selected human cancer cell lines (IC50 = 3-6 mug/mL against SK-MEL,
KB, BT-549, and SK-OV-3), and 4 was also cytotoxic to human malignant mela
noma (IC50 = 0.37 mug/mL). Sampangine (4) also inhibited cell aggregation w
ith a MIC value of <0.15 mug/mL, while 3-methoxysampangine (5) was only wea
kly active.