Pitiamides A and B, Multifunctional Fatty Acid Amides from Marine Cyanobacteria.

Two geometric isomers related to pitiamide A, termed 1E-pitiamide B (1) and 1Z-pitiamide B (2), were isolated from a marine cyanobacterium collected from the shallow reef flat at Piti Bomb Holes, Guam, Mariana Islands. The structures of these analogues were elucidated using 1D and 2D NMR analysis. Pitiamide A, which has been previously described, but has not been investigated in bioassays, was co-isolated. Pitiamides A and B were subjected to a biological evaluation and they both showed antiproliferative effects on HCT116 cells with IC50 values of 1-5 mu M. Pitiamide Awas investigated individually and caused plasma membrane hyperpolarization and an increase of intracellular calcium in HCT116 cells.