International Science and Technology Journal

In this study, six seaweeds species collected from Sosa and Hamama shores (Libya) were identified and analyzed for their antioxidant activities. Seaweeds species were identified as polysiphonia brodiaei (Dillwyn), Laurencia obtusa (Huds), Rytiphloea tinctoria (Clemente), Cystoseira compressa (Esper) , C. corniculata (Wulfen), and C.spinosa (Sauvageau). C.compressa algae recorded the highest methanolic extraction yield of 18.01 % while R.tinctoria was with the lowest one (3%). The results indicated that C. compressa species had the highest total phenolic content (TPC), reaching 514.8 mg/100g while the lowest value of 38 mg/100 was reported for R. tinctoria species. Antioxidant activities based on diphenylpicrylhydrazyl (DPPH) radical scavenging activity were assessed with 3 doses of methanolic extraction (50,100 and 200 ppm). The results showed that the methanolic extracts of sea weeds exhibited antioxidant activities with a strong dose–response. The greatest antioxidant activity value (% 90.42  0.53) was reported for P. brodiaei species at concentration of 200ppm followed by the same species at 100 ppm ( % 79.51  0.75) whereas the lowest (% 1.630.53)was obtained from methanolic extract of L.obtusa at 50 ppm. Thin layer chromatography (TLC) was used to separate and characterize the phenolic and antioxidant compounds in each extract obtained from the studied seaweeds. ferric-reducing anti-oxidant power assay was detected with methanolic extracts and all the isolated phenolic compounds that gave a blue color with ferric chloride had antioxidant activity when sprayed with DPPH• core, and thus have the ability to donate protons to free radicals. P. brodiaei and C. compressa had nearly similar effect in removing the color of the DPPH• core although the latter contained a higher concentration of phenolic substances, indicating the presence of non-phenolic compounds with high antioxidant activity. The number of isolated components with antioxidant activity increased in the species P. brodiaei, C. compressa, and R. tinctoria compared to the other species. Thus, seaweed extracts reveal promising antioxidant activities and may be candidates for food additives........... Keywords:......... Brown algae, Red algae, Phenolic substances, Antioxidants, DPPH, TLC