[Studies on chemical constituents of Laurencia saitoi].

In order to search for bioactive natural products from marine algae, the chemical constituents of red alga Laurencia saitoi was separated by the combination of normal phase silica gel, Sephadex LH-20 column chromatography and recrystallization. Seven compounds: aplysistatin (1), 5-acetoxypalisadin B (2), palisadin B (3), palisadin A (4), pacifigorgiol (5), stigmast4-en-3alpha, 6beta-diol (6), 2, 3, 5, 6-Tetrabromoindole (7), were isolated and their structures were elucidated by spectroscopic methods including 1H-NMR, 13C-NMR and MS techniques. All compounds were isolated from L. saitoi for the first time. Cytotoxicities of purified compounds were evaluated by MTT method, however, all of them were found inactive (IC50 >10 mg x L(-1).