A Novel β‐Amino Acid in Cytotoxic Peptides from the Cyanobacterium <i>Tychonema</i> sp.

Abstract

Abstract The cyclic dodecapeptides tychonamide A ( 1 ) and B ( 2 ) isolated from the methanolic extract of the cyanobacterium Tychonema sp. contain the novel β‐amino acid 3‐amino‐2,5,7‐trihydroxy‐8‐phenyloctanoic acid (Atpoa). Compounds 1 and 2 have cytotoxic activity towards cancer cell linesin a monolayer assay with mean IC 50 values of 0.9 and 3.3 μg mL –1 , respectively. Compound 2 was shown to be active against tumor cell suspensions derived fromsolid tumor xenografts in a clonogenic assay (mean IC 50 2.4 μg mL –1 ). Additionally, antiprotozoal activity was observed ( Trypanosoma b. rhodesiense , IC 50 0.1 μg mL –1 ) for compound 1 . (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2008)