Nuttingins A-F and malonganenones D-H, tetraprenylated alkaloids from the tanzanian gorgonian Euplexaura nuttingi

Six new tetraprenylated purine alkaloids, designated nuttingins A-F (1-6), were isolated together with three known malonganenones, A-C (12-14), and five new closely related malonganenones, D-H (7-11), from the gorgonian Euplexaura nuttingi collected in Pemba Island, Tanzania. The structures of the compounds were elucidated by interpretation of 1D and 2D NMR data including 15N chemical shifts obtained from H-1-N-15 HMBC spectra. Nuttingins A-E (1-5) and malonganenones D-G (7-10) displayed inhibitory activity against both K562 and UT7 tumor cell lines, compounds 3-5 being the most active ones, approximately 3-fold more potent than the others. Compounds 1-5 and 7-11 also induce apoptosis in transformed mammalian cells at a concentration of 1.25 mu g/mL.