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Seaweed is one of the largest producers of biomass in marine environment and is a rich arsenal of active metabolites and functional ingredients with valuable beneficial health effects. Being a staple part of Asian cuisine, investigations on the crude extracts of Phaeophyceae or brown algae revealed marked antitumor activity, eliciting a variety of research to determine the active ingredients involved in this potential. The sulfated polysaccharide of fucoidan and carotenoid of fucoxanthin were found to be the most important active metabolites of brown algae as potential chemotherapeutic or chemopreventive agents. This review strives to provide detailed account of all current knowledge on the anticancer and antitumor activity of fucoidan and fucoxanthin as the two major metabolites isolated from brown algae. 

Fungal infections are the main cause of decay on fresh fruit during postharvest phase determining severe losses. Postharvest control is performed by fungicides, but their intense use have aroused issue relating to environmental protection and human health prompting to search alternative control means. The use of biofuel-used seaweed extracts by a supercritical carbon dioxide technique could be a valid alternative during postharvest handling of fresh fruit. The aim of this work was to assess the in vitro and in vivo activity of extracts from two brown seaweeds (Laminaria digitata and Undaria pinnatifida) and three red seaweeds (Porphyra umbilicalis, Eucheuma denticulatum and Gelidium pusillum) against three postharvest pathogens (Botrytis cinerea, Monilinia laxa and Penicillium digitatum) using three concentrations of extract (10, 20 and 30 g L−1). The total content of fatty acids of the extracts was determined by CG-MS, those of polysaccharides by HIC, and phenolic compounds (phlorotannins) by HPLC-DAD. Twenty fatty acids were quantified in the extracts, while three polysaccharides categories and three phlorotannins classes were identified only in brown seaweed extracts. L. digitata, U. pinnatifida and P. umbilicalis showed the highest antifungal efficacy on in vitro cultures of the pathogens. L. digitata and U. pinnatifida completely inhibited mycelia growing and conidial germination of B. cinerea and M. laxa at the highest dose tested and strongly reduced those of P. digitatum. P. umbilicalis extract strongly inhibited mycelia and conidia growth on all the fungi. E. denticulatum and G. pusillum showed a lower but still significant reduction of mycelia growing and conidia germination on all the pathogens. In trials performed in vivo on wounded fruit, L. digitata, U. pinnatifida and P. umbilicalis extracts strongly suppressed grey mould on strawberries, brown rot on peaches, and green mould on lemons at 30 g L−1 dose both in preventive and curative treatments; E. denticulatum and G. pusillum poorly reduced disease development. In all cases, a dose-effect of the treatments was observed with an increase of fruit decay inhibition and reduction of disease severity as the dose of extract applied over the wound increased. Moreover, an increased peroxidase activity in the strawberries/B. cinerea and peaches/M. laxa systems by preventive treatment with 30 g L−1 extract was observed. The antifungal activity could be mainly ascribed to a direct toxicity of fatty acids found at the highest concentrations in L. digitata, U. pinnatifida and P. umbilicalis rather than to those of phenolic compounds and phlorotannins; but it could be related to possible peroxidase-mediated systemic resistance mechanisms elicited by the polysaccharides.

Dietary Laminaria and Porphyra sp. have been reported to reduce the risk of intestinal or mammary cancer in animal studies. Algal anticarcinogenicity may involve effects on cell proliferation and antioxidant activity. Thus, in the present study, we evaluated the effect of red alga, dulse (Palmaria palmata) and three kelp (Laminaria setchellii, Macrocystis integrifolia, Nereocystis leutkeana) extracts on human cervical adenocarcinoma cell line (HeLa cells) proliferation using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay. The 1-butanol soluble fractions from the methanol extracts of these algae were also evaluated for reducing activity and total polyphenol content. After 72 h incubation, HeLa cell proliferation was inhibited (p < 0.05) between 0% and 78% by P. palmata; 0% and 55% by L. setchellii and 0% and 69% by M. integrifolia and N. leutkeana at 0.5–5 mg/mL algal extract. Algal extract reducing activities were as follows: P. palmata > M. integrifolia > L. setchellii > N. leutkeana; and total polyphenol contents were: P. palmata > M. integrifolia = N. leutkeana > L. setchellii. The antiproliferative efficacy of these algal extracts were positively correlated with the total polyphenol contents (p < 0.05), suggesting a causal link related to extract content of kelp phlorotannins and dulse polyphenols including mycosporine-like amino acids and phenolic acids.

Background: Ulva genus, an edible seaweed, and an important food source in many south-east Asian countries is also recognized by its synonymous name as Enteromorpha.

Objectives: This study was carried out to evaluate antioxidant activity, contents of total phenolics, and flavonoids of methanolic extracts of edible green seaweeds including Ulva clathrata (Roth) C. Agardh and three samples of Ulva prolifera O.F.Müller grown at different parts of Bushehr Province along the northern coasts of the Persian Gulf.

Materials and Methods: The seaweeds were collected from Bordekhoun, Northern Ouli, Taheri and Kangan coasts in December 2011. Methanolic extracts of the seaweeds were assessed for their antioxidant activity using DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging assay and was performed in a microplate reader. Total phenolics were determined by Folin-Ciocalteu reagent and flavonoid content was evaluated by colorimetric method.

Results: All samples showed antioxidant activity to various degrees. Ulva clathrata exhibited a high DPPH radical scavenging activity with a low IC50 (the half-maximal inhibitory concentration) (0.715 ± 0.078 mg. mL-1). The highest phenolic content (4.468 ± 0.379 mg GAE g-1) (gallic acid equivalent) and flavonoid content (45.577 ± 0.949 mg RE g-1) (rutin equivalent) were also observed in U .clathrata. The phenolic and flavonoid contents showed positive correlations with the DPPH radical scavenging activity and negative correlations with IC50 (P < 0.01). Besides, Results showed that there was a positive correlation between total phenolics and flavonoid content of extracts (P < 0.01).

Conclusions: Strong positive and significant correlations between DPPH radical scavenging and phenolic and flavonoid contents showed that, phenolic compounds, including flavonoids are the main contributors of antioxidant activity in these Ulva species and variations in phenolics and flavonoid contents of the seaweed extracts may be due to the variation in physicochemical parameters such as salinity amongst the selected stations.