Biselyngbyolide B, a Novel ER Stress-inducer Isolated from the Marine Cyanobacterium Lyngbya sp.

A novel cytotoxic macrolide biselyngbyolide B (1) was isolated from the marine cyanobacterium Lyngbya sp., collected on Ishigaki Island, Japan. The structure of 1 was determined to be the aglycone of biselyngbyaside (2) on the basis of 1D and 2D NMR spectra and CD data. The apoptosis-inducing activity of 1 was 30- to 100-fold greater than that of 2. In addition, 1 was found to exhibit ER stress-inducing activity.