Albopunctatone, an Antiplasmodial Anthrone-Anthraquinone from the Australian Ascidian Didemnum albopunctatum

Chemical investigation of a MeOH extract of the Great Barrier Reef ascidian Didemnum albopunctatum has led to the isolation and identification of a new anthrone-anthraquinone, albopunctatone (1), together with the known 1,8-dihydroxy-9,10-anthraquinone (2). The structure of 1 was established from interpretation of 1D and 2D NMR spectroscopic and mass spectrometric data. The compounds were screened for antiplasmodial activity against chloroquine-resistant and -sensitive strains of the malaria parasite, Plasmodium falciparum. Albopunctatone (1) was moderately active against both strains (IC50 5.3 and 4.4 +/- 0.5 mu M, respectively), while 2 was inactive at doses up to 40 mu M. Both compounds were also inactive up to 40 mu M when tested against a variety of cancerous and normal human cell lines and the kinetoplastid Trypanosoma brucei brucei, indicating selectivity for the malaria parasite, P. falciparum.