Two New Meroterpenoid Derivatives From Sargassum macrocarpum With Their Anti-Oxidant Activities

Objective: The purpose of this study was to search for novel secondary metabolites present in the marine brown alga, Sargassum macrocarpum C. Agardh. Methods: The methanolic extract of S. macrocarpum was partitioned and fractionated using a silica gel column, medium pressure liquid chromatography, and preparative-high performance liquid chromatography to obtain four compounds (1-4). These structures were elucidated using nuclear magnetic resonance spectroscopic and high resolution-electrospray ionization-mass spectroscopy methods. The isolated compounds were evaluated for their anti-oxidant activities using 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals. Result: Two undescribed meroterpenoid derivatives (1 and 2), together with two known racemic meroterpenoids (3 and 4) were isolated from the methanolic extract of S. macrocarpum. All compounds were confirmed to be meroterpenoid derivatives. All these compounds exhibited ABTS and DPPH radical scavenging activities. Conclusions: The four meroterpenoids (1-4) were isolated from S. macrocarpum. Compound 3 showed the most anti-oxidant effect with IC 50 values of 9.9 (ABTS radical) and 22.4 μM (DPPH radical), respectively.