10.22376/ijpbs.2019.10.1.p1-12 Volume 3 Issue 3 2012 (July - September) Sulfated polysaccharides from brown seaweeds attracted extensive interest due to their numerous biological activities and structural diversity. Sulfated polysaccharides isolated from lessThan i greaterThan Sargassum siliquosum lessThan /i greaterThan J. G Agardh were investigated for its chemopreventive potential using lessThan i greaterThan in vitro lessThan /i greaterThan assays. Estimation of chemopreventive activity included antioxidant (cancer anti-initiation); Nitrite Assay (cancer anti-promotion) and cytotoxicity (cancer anti-progression) assays representing the 3 stage paradigm of carcinogenesis. Extracted water soluble polysaccharides containing sulfate were identified by FT-IR and Ashing Acid Digestion Ion chromatography with IR spectra comparable to standard fucoidan and alginate. Sulfated polysaccharides showed significant radical scavenging activity in DPPH radicals, significantly suppressed production of nitric oxide in LPS-stimulated promyelocytic leukemic cells (PML) and displayed significant antiproliferative activity in both Hep G2 and renal carcinoma cells lessThan i greaterThan in vitro lessThan /i greaterThan . Results herein indicated that sulfated polysaccharide of lessThan i greaterThan S. siliquosum lessThan /i greaterThan possesses chemopreventive activities and their use as potential natural reagents might for cancer therapy should be given priority. Ross D. Vasquez, John Donnie A. Ramos, Samuel D. Bernal Sargassum siliquosum, sulfated polysaccharide, ashing-acid digestion, antioxidant, nitric oxide, antitumor activity 333-345