Two New Cytotoxic C-29 Steroids from the Red Sea Brown Alga Cystoseira trinodis

摘要

Chromatographic fractionation of the organic extract obtained from the brown alga Cystoseira trinodis led to the isolation of a known carotene pigment (7), five C-29 steroids (2-6), including two new ones (2 and 5), and an unexpected metabolite, halogenated cyclic ene-yne ether (1). Compound 1 was isolated from the genus Cystoseira for the first time. This finding plays an important role in the chemo-taxonomical differentiation of C. trinodis from other Cystoseira species. All compounds (1-7) were evaluated for their in vitro cytotoxic activities against four human tumor cell lines MCF-7, HepG2, WI 38, and Vero. They showed moderate cytotoxicity with IC50 in the range 7-33 mu M, where 7 exhibited the highest antioxidant activity with 72.1% inhibition.