PLAKORTIDES, NOVEL CYCLIC PEROXIDES FROM THE SPONGE PLAKORTIS HALICHONDRIOIDES - ACTIVATORS OF CARDIAC SR-CA(2-PUMPING ATPASE())

As part of a search for novel activators of Ca2+ pumping activity of c ardiac SR-(sarcoplasmic reticulum), the EtOAc extract of the Jamaican sponge Plakortis halichondrioides was shown to be active. Bioassay-gui ded fractionation of the extract followed by preparative TLC and HPLC yielded several known and novel compounds. Three of the novel cyclic p eroxides, plakortides F, G, and H (3, 4, and 5) are the subject of thi s report. Their structures including relative stereochemistry were est ablished by interpretation of spectral data. Micromolar concentrations of plakortides F-H (3-5) were found to significantly enhance Ca2+ upt ake by SR.