Antioxidant Activities Measurement of Brown Seaweed (Sargassum honeri) Extracts using Supercritical Carbon Dioxide and Subcritical Water Yin Shipeng1, Hee-Chul Woo2 and Byung-Soo Chun1*  1 Department of Food Science and Technology, Pukyong National University, 45 yongso-ro, Nam-gu, Busan 608- 737, Korea *E-mail: bschun@pknu.ac.kr, TEL: +82-51-629-5830, FAX: +82-51-629-5824 2 Department of Chemical Engineering, Pukyong National University, Busan 608-739, Korea Abstract Seaweeds are potential renewable resource in the marine environment. It has unexplored bioactive compounds, which could be potentially as functional food for human health. Seaweed provides for an excellent source of bioactive compounds, such as carotenoid, dietary fiber, protein, vitamins, essential fatty acid, and minerals. Interestingly, seaweeds are a rich source of phytochemicals having anti-oxidant and antimicrobial properties. Among the functional effects of the seaweed, nutritional and health-related benefits have been widely studied. Most of seaweed has the anti-tumor, antifungal, anti-inflammatory, antioxidant and a wide range of biological activities. In this study, seaweed (Sargassum honeri) was extracted using an environmental friendly solvent, supercritical carbon dioxide (SC-CO2). The SC-CO2 will be carried out at constant temperature 45℃ and pressures ranging from 20MPa. It will be produced by the subcritical water hydrolysis (SWH) with the reaction temperatures for hydrolysis will be maintained from 180 to 260℃. The SWH will be done with condition 16-220 bar for the reaction pressure and 1:25 (w/v) for the ratio of material to water. High pressure pump will be applied to flow water from tank to reactor for getting initial pressure 1 bar. The antioxidant activities produced will be determined by using the ABTS, TPC, TFC, and DPPH method. The 1% formic acid and 1% sodium bicarbonate which will used as catalyst will suspended in 150ml of distilled water. Materials & Methods Results Materials ABTS,DPPH ,TPC and TFC The Sargassum honeri samples were dried in a freeze-drier (-80°C) for about 72 hours. The dried samples were crushed using mechanical blender and sieved (710 µm) by mesh. These samples were then stored at -20°C and used for subcritical water hydrolysis (SWH) extraction. ABTS Supercritical carbon dioxide (SC-CO2) Sample amount : 100 g Extraction vessel: 200 mL CO2 flow rate: 27 g/min Temperature (oC) : 45 Pressure (bar) : 200 Extraction time: 2 h Fig 1；Schematic diagram of Supercritical carbon dioxide Fig. 3. ABTS of Sargassum honeri hydrolyzates at different temperatures and pressures Fig. 4. DPPH of Sargassum honeri hydrolyzates at different temperatures and pressures TPC TFC Subcritical Water Hydrolysis (SWH) Sample amount : 6 g Material to water ratio : 1：33 Initial pressure (bar)：1 Temperature (o C) : 180 – 260 Pressure (bar) : 16-220 Agitation speed: 150 rpm Heating time : 20-60 min Fig 2；Schematic diagram of Subcritical Water Hydrolysis Fig. 5. Total Phenolic Content of Sargassum honeri hydrolyzates at different temperatures and pressures Fig. 6. Total Flavonoid Content of Sargassum honeri hydrolyzates at different temperatures and pressures Antioxidant Test Antioxidant activities and compounds were found in all hydrolyzates and it was varied with different temperatures, pressure and catalyst. The best temperature to gain the best antioxidant properties was found at 260 ℃. Highest ABTS and DPPH were found in subcritical water extracted from Sargassum honeri hydrolyzates at 260°C/220bar and it was 93.24% with formic acid and 21.36% with formic acid. Highest Total Phenolic Content (TPC) and Total Flavonoid (TFC) were found in subcritical water extracted Sargassum honeri hydrolyzates at 260 °C/220bar and it was 557ug/L and 198ug/L with formic acid. The seaweed hydrolyzate product will be subjected to antioxidant capacity assays, which are 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2’-azinobis(3-ethylbenzothiazoline-6-sulphonic acid)(ABTS) radical scavenging capacity assays and antioxidant compounds assays, including total phenolic content (TPC) and total flavonoid content (TFC) assay. Acknowledgement This research was supported by the Ministry of Oceans and Fisheries (2013-1039449) Conclusion Due to energy saving, environmentally friendly and cost effective subcritical water hydrolysis has great potential for food industries. Sargassum honeri hydrolyzates can be used in food systems as a natural additive possessing a wide range of antioxidative properties. 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