The antioxidative potential of different fractions (respective organic and aqueous fractions of n-hexane, chloroform and ethyl acetate) of 70% methanol extract of Ecklonia cava(a brown seaweed) was evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH), superoxide anion, hydrogen peroxide, hydroxyl radical, nitric oxide, ferrous ion chelating, reducing power and lipid peroxidation inhibition (conjugated diene hydroperoxide and thiobarbituric acid-reactive substances production) assays. The 70% methanol extract showed significant (p< 0.05) activities in all antioxidant assays and contained a high level of total phenolic content. It was observed that the level of hydrophilic phenolic content was higher than that of hydrophobics. Among those organic solvent fractions, ethyl acetate fraction exhibited significant activities due to the highest level of total phenolic content and their IC50 values were 0.013mg/mL, 0.009mg/mL and 0.33mg/mL in DPPH, hydrogen peroxide and nitric oxide radical inhibition, respectively. These activities were superior to those of a commercial synthetic and natural antioxidants tested. The aqueous chloroform and ethyl acetate fractions also exhibited significant (p< 0.05) activities in reactive oxygen species (ROS) scavenging and metal chelating, attributed to the high amount of hydrophilic phenolics. Moreover, E. cava extracts showed strong reducing power and a notable capacity to suppress lipid peroxidation.

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A sulfated polysaccharide purified from a brown alga Ecklonia cava, having high anticoagulant activity was investigated for its antiproliferative effect on murine colon carcinoma (CT-26), human leukemic monocyte lymphoma (U-937), human promyelocytic leukemia (HL-60), and mouse melanoma (B-16) cell lines. The sulfated polysaccharide isolated and purified from an enzymatic extract of E. cava had a good selective tumor cell growth inhibition effect; its effect on HL-60 and U-937 was especially promising. The IC 50 value for the sulfated polysaccharide from E. cava (ECSP) on U-937 was 43.9 μg mL −1 . The presence of the sample in the cell culture media stimulated the induction of apoptosis, revealed by nuclear staining with Hoechst 33342. The apoptosis induction was confirmed by the cell cycle analysis, while pronounced sub-G1 phase arrests of 9.5% and 13.8% were also clearly observed when the cells were treated at 15 and 30 μg mL −1 of ECSP in the U-937 cell line, respectively. After a 24-h incubation period, ECSP dose-dependently enhanced the DNA fragmentation on the U-937 cell line as observed in the agarose gel electrophoresis assay. To rule out the action mechanism of ECSP for its anticancer activity, some western blot analyses were conducted with several antibodies (caspase-7, caspase-8, Bax, Bcl-xL, and PARP) and ECSP had a clear effect on the caspase -7 and 8 which cleave protein substrates, including PARP, an inducer of apoptosis responsible for DNA cleavage. Moreover, ECSP controlled the cellular transmembrane molecules like Bax and Bcl-xL. Taken together, the above results demonstrate that the apoptosis for antiproliferative effect of ECSP was clearly induced on U-937 cells.

Effective extraction of algal bioactive compounds can be achieved by treatments such as pH control, heat and enzymatic hydrolysis. Hizikia fusiformis antioxidants were extracted with those treatments individually and extraction efficacies were compared by measuring yield, total phenolic content and antioxidant activities. Increased pH could successfully improve the extraction, and incubation at pH 12.0 for 12 h was the most effective pH treatment. Incubation at 100°C for 45 min was significantly (P < 0.05) more effective than the other heat treatments. Optimum condition for enzymatic treatment was combination of 2% Alcalase (alkaline endopeptidase/protease) and 3% Ultraflo (b-glucanase/carbohydrase) at pH 8.0 and 54-58°C for 24 h. Integration of those optimised treatments in the extraction sequence of heat (H), enzymatic hydrolysis (E) and pH control (P) was the most effective sequence. Compared with other extraction sequences, HEP sequence indicated significantly higher phenolic content and antioxidative activities in 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydrogen peroxide scavenging assays.

The results of this study suggest that quercetagetin could be used in the functional food, cosmetic and pharmaceutical industries.