Fucoxanthin, one of the main marine carotenoids, is abundant in macro- and microalgae. Here, fucoxanthin was isolated and structurally identified as the major carotenoid in the diatom Phaeodactylum tricornutum through chromatographic and spectroscopic methods, such as liquid chromatography-positive-ion atmospheric pressure chemical ionization/mass spectroscopy and nuclear magnetic resonance. This pigment was quantified by reverse-phase high-performance liquid chromatography, and a number of extraction procedures were assessed to investigate the effect of solvent type, extraction time, temperature, and extraction method (maceration, ultrasound-assisted extraction, Soxhlet extraction, and pressurized liquid extraction). Among the investigated solvents, ethanol provided the best fucoxanthin extraction yield (15.71 mg/g freeze-dried sample weight). Fucoxanthin content in the extracts produced by the different methods was quite constant (15.42-16.51 mg/g freeze-dried sample weight) but increased steeply based on the percentage of ethanol in water, emphasizing the importance of ethanol in the extraction. The results indicate that P. tricornutum is a rich source of fucoxanthin (at least ten times more abundant than that in macroalgae) that is easily extracted with ethanol, suggesting potential applications in human and animal food, health, and cosmetics.

Fucoidans were isolated by water extraction and ion-exchange chromatography from brown algae Eclonia cava, Sargassum hornery, and Costaria costata collected near of Korean coasts. The structures of fucoidans were investigated. Fucoidan from E. cava was mixture of sulfated rhamnogalactofucan and galactofucan. Fucoidan from C. costata was a sulfated galactofucan. Fucoidan isolated from S. hornery was separated into three fractions: a homofucan sulfate, a homofucan but without sulfate groups, and a sulfated rhamnofucan. The results clearly showed that fucoidans play an inhibitory role in colony formation in human melanoma and colon cancer cells and may be effective antitumor agents.

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The plant Ligularia fischeri var. spiciformis Nakai, a well-known edible medicinal herb in Korea, has been used to treat maladies such as jaundice, scarlet fever, rheumatoid arthritis, and hepatic function failure. In this research, 4 major antioxidant compounds were detected from this plant's leaves using an on-line high-performance liquid chromatography (HPLC)-ABTS screening system, which can determine the antioxidant activity based on a decrease in absorbance at 734 nm after postcolumn reaction of HPLC-separated antioxidants with the 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radicals (ABTS(*)). In order to isolate these active compounds, a preparative HPLC was applied and their chemical structures were identified as 5-O-caffeoylquinic acid (5-CQA), 3,4-di-O-caffeoylquinic acid (3,4-DCQA), 3,5-di-O-caffeoylquinic acid (3,5-DCQA), and 4,5-di-O-caffeoylquinic acid (4,5-DCQA) by ESI/MS(n) and (1)H NMR. These 4 isomers comprised over 10% of the dried leaves, with 3,5-DCQA being the most abundant compound. The radical scavenging activity of each isomer was also evaluated simultaneously through the on-line HPLC-ABTS method, which showed 94% antioxidant activity of the ethanol extract derived from caffeoylquinic acids. Among these isomers, 3,4-DCQA contained the most strong antioxidant activity while 3,5-DCQA accounted for the highest radical scavenging capacity due to having the highest content.