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 (), lamellarin-η (), lamellarin-ϕ () and lamellarin-χ () along with seven known lamellarins, lamellarin-K (), lamellarin-I (), lamellarin-J (), lamellarin-K triacetate (), lamellarin-L triacetate (), lamellarin-F () and lamellarin-T diacetate (). The structures of the compounds were established by detailed analysis of NMR spectral data. Cytotoxic activity of the isolates has been done against coloractal cancer cells.