Abstract
The organic extract of Sargassum siliquastrum exhibited in vitro radical scavenging activity in our screening of marine brown algae collected in Jeju Island, Korea. Bioactivity-guided fractionation of the organic extract led to the isolation of two new meroterpenoids, named sargachromanols S and T, along with the known meroterpenoids, isopolycerasoidol, nahocol D2, and sargachromanols D, E, G, and I. The planar structures of the new compounds were determined by the analysis of spectroscopic data obtained by HREIMS and 1D and 2D NMR. The structures of the new compounds sargachromanols S and T were closely related to those of previously isolated sargachromanols D and A, respectively. The isolated compounds showed radical scavenging activities in vitro against 1,1-diphenylpicrylhydrazyl and 2,2'-azidobis(3-ethylbenzothiazoline-6-sulfonate) radicals.