Methanolic extracts (MEs) of seven brown seaweeds occurring in the Indian coastal waters were screened for their cytotoxic and antioxidant properties following various assays. The methanolic extracts of seaweeds in the order of Dictyopteris australis > Spatoglossum variabile > Stoechospermum marginatum > Spatoglossum aspermum showed significant cytotoxic activity. A very high DPPH radical scavenging activity was exhibited by the methanolic extracts prepared from St. marginatum, Padina tetrastromatica, Dictyopteris delicatula and S. aspermum. The total phenolic content of the MEs varied from 13.19 ± 0.32 to 25.29 ± 0.445 gallic acid equivalents (mg g−1 of methanolic extract). The reducing power assay indicated a dose dependency, at concentrations of 0.1, 0.5 and 1.0 and 2.0 mg mL−1 of MEs and decreased in the following order: Butylated hydroxy toluene > P. tetrastromatica > D. delicatula > S. aspermum > S. variabile > S. marginatum > D. australis > S. marginatum. Furthermore, D. australis, S. aspermum, S. variabile and S. marginatum demonstrated good metal ion chelating properties. All the above evidences suggest that, the antioxidant compounds found in brown seaweeds scavenge free radicals through effective intervention. This decisively promotes them as a potential source of natural antioxidants.
The underlying results endorse seaweeds as a rich, novel source of antioxidant compounds needing systemic exploration.
BACKGROUND/OBJECTIVESAbundant 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/METHODSAmong 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.RESULTSMost 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.CONCLUSIONSAltogether, 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.
This article evaluates the cytotoxic and antioxidant activities of the seaweeds Amphiroa fragilissima and Asparigopsis taxiformis methanolic extracts in-vitro. The aim of this study was to test the selected red seaweed extracts for their cytotoxic activity by Brine shrimp lethality assay and antioxidant properties by in-vitro free radical scavenging assays such as, 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay, reducing power assay, and metal ion chelating assay. Also, the total phenolic content (TPC) of the seaweed extracts was also determined. In the brine shrimp lethality test, A. fragilissima and A. taxiformis demonstrated mild cytotoxic activity of 53.33 ± 2.58 and 58.33 ± 2.58 % at the highest concentration of 0.5mg/ml and 24 h incubation time. The total phenolic content of both the seaweed extracts were expressed as mg gallic acid equivalent (GAE)/ gram dry seaweed extract and consecutively decreased as follows: A. taxiformis (8.521 ± 0.284) > A. fragilissima (8.220 ± 0.214). Percent DPPH radical scavenging activities of the two studied red seaweed extracts were dose dependant and was highest in the extract of A. fragilissima (IC50 2.89 ± 0.061 mg/ml) when compared to A. taxiformis (IC50 3.38 ± 0.042 mg/ml), although none showed comparable activity to the standard ascorbic acid (ICM50 0.07 ± 0.002 mg/ml). Reducing power in seaweed methanolic extracts at all concentrations of 0.1, 0.5 and 1.0 and 2.0 mg/ml decreased in the order of BHT > A. fragilissima > A. taxiformis. The metal ion chelating efficacy was the highest in A. fragilissima (IC501.27 ± 0.018 mg/ml) followed by A. taxiformis (IC50 2.37 ± 0.172 mg/ml), respectively. The present study exemplifies that the methanolic extracts of Amphiroa fragilissima and Asparigopsis taxiformis have notable cytotoxic and antioxidant activities in in-vitro assay systems.
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