Pitipeptolides A and B, new cyclodepsipeptides from the marine cyanobacterium Lyngbya majuscula

Two new cyclodepsipeptides have been isolated from a population of the marine cyanobacterium Lyngbya majuscula collected at Piti Bomb Holes, Guam. They appear to be unique to this particular Guamanian collection and have been named pitipeptolides A (1) and B (2). Their structures have been elucidated by spectroscopic techniques and by characterization of degradation products. Distinctive features include the presence of a 2,2-dimethyl-3-hydroxy-7-octynoic acid residue in 1 and a 2,2-dimethyl-3-hydroxy-7-octenoic acid residue in 2, previously shown to be biosynthetic signatures of cyanobacterial metabolites. Pitipeptolides A (1) and B (2) exhibit weak cytotoxicity against LoVo cancer cells, but possess moderate antimycobacterial activity and stimulate elastase activity.