New potent cytotoxic lamellarin alkaloids from Indian ascidian Didemnum obscurum

Chemical investigations of the ascidian Didemnum obscurum has resulted in the isolation of four new lamellarin alkaloids, lamellarin-ζ (1), lamellarin-η (2), lamellarin-? (3) and lamellarin-χ (4) along with seven known lamellarins, lamellarin-K (5), lamellarin-I (6), lamellarin-J (7), lamellarin-K triacetate (8), lamellarin-L triacetate (9), lamellarin-F (10) and lamellarin-T diacetate (11). The structures of the compounds 1-11 were established by detailed analysis of NMR spectral data. Cytotoxic activity of the isolates has been done against coloractal cancer cells.