A unique
prenylated bicarbazole alkaloid, clausanisumine (1),
and two biogenetically related known monomer carbazole
alkaloids, mukonal (2) and 3-methylcarbazole (3), were isolated from the fruits of Clausena anisum-olens. Clausanisumine (1) was an uncommon prenylated bicarbazole
alkaloid, possessing an unprecedented carbon skeleton, which was composed
of a simple carbazole alkaloid and a prenylated carbazole alkaloid.
The chemical structure of 1 was established by a combination
of comprehensive spectral methods. A plausible biosynthetic pathway
of 1 was also proposed. Additionally, the potential anti-HIV
activities of all isolates 1–3
in vitro were evaluated. Compound 1 exhibited
remarkable anti-HIV-1 reverse transcriptase effects showing an EC50 value of 18.58 nM. The discovery of the prenylated bicarbazole
alkaloid from C. anisum-olens with
notable anti-HIV activity would be meaningful to discovering and developing
new anti-HIV drugs.