New bisabolane-type phenolic sesquiterpenoids from the marine sponge Plakortis simplex

Six new bisabolane-type phenolic sesquiterpenoids, including plakordiols A−D ( 1−4 ), (7R, 10R)-hydroxycurcudiol ( 5 ) and (7R, 10S)-hydroxycurcudiol ( 6 ) were isolated from the marine sponge Plakortis simplex collected from the South China Sea. Their structures were determined based on extensive analysis of spectroscopic data. Their configurations were assigned by coupling constant analysis, NOESY correlations, and the modified Mosher’s method. Furthermore, their cytotoxic and antibacterial activities were evaluated.