Preparative separation of three terpenoids from edible brown algae Sargassum fusiforme by high-speed countercurrent chromatography combined with preparative high-performance liquid chromatography

Edible brown algae Sargassum fusiforme is an economic seaweed with huge yield in Asia. Terpenoids are an important class of active substances in Sargassum fusiforme, which have replaced some synthetic drugs in clinical treatment. In this work, the preparative separation protocol of three terpenoids, loliolide (1), isololiolide (2), and (3R)-4-[(2R,4S)-4-acetoxy-2-hydroxy-2,6,6-trimethylcyclohexylidene]-3-buten-2-one (3), from Sargassum fusiforme by high-speed countercurrent chromatography combined with preparative high-performance liquid chromatography was presented. n-Hexane-ethyl acetate-methanol-water (1:2:1:2, v/v) was selected as biphasic solvent system through optimization. Under the optimal high-speed countercurrent chromatography separation conditions, 35.87 mg mixture of isomers 1 and 2, and 8.87 mg compound 3 were obtained from 300 mg of the crude extract of Sargassum fusiforme. The isomer mixture was further separated by preparative high-performance liquid chromatography to obtain 11.56 mg compound 1 and 12.82 mg compound 2. Their purities were all above 95%. The chemical structures of three isolated terpenoids were identified by 1H and 13C nuclear magnetic resonance spectroscopy.