Digital library

BACKGROUND/OBJECTIVES: Abundant consumption of seaweeds in the diet is epidemiologically linked to the reduction in risk of developing cancer. In larger cases, however, identification of particular seaweeds that are accountable for these effects is still lacking, hindering the recognition of competent dietary-based chemo preventive approaches. The aim of this research was to establish the antiproliferative potency and angiosuppressive mode of action of Stoechospermum marginatum seaweed methanolic extract using various experimental models. 

MATERIALS/METHODS: Among the 15 seaweeds screened for antiproliferative activity against Ehrlich ascites tumor (EAT) cell line, Stoechospermum marginatum extract (SME) was found to be the most promising. Therefore, it was further investigated for its anti-proliferative activity in-vitro against choriocarcinoma (BeWo) and non-transformed Human embryonic kidney (HEK 293) cells, and for its anti-migratory/tube formation activity against HUVEC cells in-vitro. Subsequently, the angiosuppressive activity of S. marginatum was established by inhibition of angiogenesis in in-vivo (peritoneal angiogenesis and chorioallantoic membrane assay) and ex-vivo (rat cornea assay) models. 

RESULTS: Most brown seaweed extracts inhibited the proliferation of EAT cells, while green and red seaweed extracts were much less effective. According to the results, SME selectively inhibited proliferation of BeWo cells in-vitro in a dose-dependent manner, but had a lesser effect on HEK 293 cells. SME also suppressed the migration and tube formation of HUVEC cells in-vitro. In addition, SME was able to suppress VEGF-induced angiogenesis in the chorio allantoic membrane, rat cornea, and tumor induced angiogenesis in the peritoneum of EAT bearing mice. A decrease in the microvessel density count and CD31 antigen staining of treated mice peritoneum provided further evidence of its angiosuppressive activity. 

CONCLUSIONS: Altogether, the data underline that VEGF mediated angiogenesis is the target for the angiosuppressive action of SME and could potentially be useful in cancer prevention or treatment involving stimulated angiogenesis. 

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.

The underlying physiology of algal antioxidant compounds is reviewed in the context of seaweed biology and utilization. The application of seaweed antioxidants in foods, food supplements, nutraceuticals and medicine is considered from the perspective of benefits to human health. We advocate that direct consumption of seaweed products for their antioxidant composition alone provides a useful alternative to non-natural substances, while simultaneously providing worthwhile nutritional benefits. Economic utilization of seaweeds for their antioxidant properties remains in its infancy. This review provides examples ranging from laboratory studies through to clinical trials where antioxidants derived from seaweeds may provide major health benefits that warrant subsequent investigative studies and possible utilization.