Studies on the antioxidative activities of seaweed Gracilaria Gigas extracts

• Main Authors: Chih-Yuan Lin, 林志遠
• Other Authors: Jing-Iong Yang
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/55021844241723270321

碩士 === 國立高雄海洋科技大學 === 水產食品科學研究所 === 97 === Freeze-dried red seaweed Gracilaria gigas was individually extracted with six different solvents including 90oC hot water (HW), cold water (CW), methanol (MT), ethanol (ET), acetone (AT) and n-butanol (BT). The six extracts were then measuremed their antioxidant activities and analyzed antioxidant compounds in their individual composition. The results indicated that the DPPH free radical scavenging of HW extract (4 mg/ml) possessed the highest activity (62%) among all extracts and that of CW, MT, ET, BT AT extracts was 55, 49, 39, 34, 21 %, respectively. The HW extract (4 mg/ml) also had the highest superoxide anion scavenging activity (89 %) and that of the 4 mg/ml CW, MT, ET, AT extracts was 84, 70, 66, and 35 %, respectively. However, BT extract did not show superoxide anion scavenging. The ET extract demonstrated the highest reducing power among all extracts and that of MT, BT, AT, CW, and HW extracts showed a decreasing tendency in the activity. Metal ion chelating activity (%) of BT extract was 75 % and that of AT and HW was 63 and 23 %, respectively. However, MT, ET, and CW extracts did not display chelating activity. It indicated that the inhibition of lipid peroxidation in a linoelic acid emulsion of 4 mg/ml of MT, ET, BT AT extracts was similar to that of 10 ppm BHA. However, HW and CW extracts exhibited weaker action in lipid peroxidation inhibition. In the FeSO4/H2O2 mediated DNA damage model, we found that AT and ET extracts demonstraded an effective protection effect on DNA oxidative damage. Moreover, the analysis of compounds with antioxidant potential in the extracts showed that CW extract has the highest contents of total phenols, ascorbic acid, and flavonoids. The ET extract is the richest in the content of carotenoid. The HW extract contains the highest amount of sulfate esters among all extracts. Some functional activities of oligosaccharides derived from red algae have been reported. The second part of this study was to investigate hydrolytic oligosaccharides from Gracilaria gigas using the agar-degrading enzyme (ADE) produced by a marine bacterium Flammeovirga YT strain isolated from a Gracilaria gigas aquacultural field in Kaohsiung country. We first searched the best reaction condition for the production of oligosaccharides from Gracilaria gigas with YT-ADE hydrolysis and then identifid oligosaccharides by using gel filtration chromatography and thin layer chromatography. The results showed that the optimal hydrolysis time was 6 h and the optimal dose of YT-ADE was 300 U. We found that the hydrolytic oligosaccharides contained neoagarohexaose, neoagarotetrose, and neoagarobiose that have the potential for developing functional food and food supplement.