Effect of storage time on phlorotannin content and antioxidant activity of six Sargassum species from Nhatrang Bay, Vietnam

The phlorotannin content and the total antioxidant, reducing power and DPPH free-radical-scavenging activities in relation to postharvest storage time of six Sargassum species (Sargassum mcclurei, Sargassum polycystum, Sargassum oligocystum, Sargassum serratum, Sargassum aquifolium, and Sargassum denticarpum) commonly found growing in the tropical marine area of Nhatrang, Khanhhoa Province, Viet Nam, were investigated. The results showed that phlorotannin content with total antioxidant and reducing power activity, and DPPH free radical scavenging of Sargassum aquifolium species were the highest, corresponding to 6.770 +/- 0.001 mg phlorotannin g(-1) DW, 6.1290 +/- 0.0200 mg ascorbic acid g(-1) DW, 19.7210 +/- 0.0300 mg FeSO4 g(-1) DW and 76.28 +/- 0.20 % of 25 mu g DPPH mL(-1) extract. The change (decline) of phlorotannin content with antioxidant activities in Sargassum polycystum occurs the fastest. The storage time of the algae descends in the following species order such as S. oligocystum > S. mcclurei, S. aquifolium > S. serratum > S. denticarpum > S. polycystum.