Abstract: With gallic acid as the standard,the content of phlorotannins in Sargassum horneri was determined by UV-visible spectrophotometric method using Folinphenol (Folin-Ciocalteu).The detection wavelength was set at 760 nm.The color reaction was carried out with 1.25 mL of Folin-Ciocalteu reagent and 4.0 mL of 0.1 g/mL aqueous Na₂CO₃ solution in darkness at 30 ℃ for 60 min.The linear range of the established standard curve was 15-50 μg/mL and the regression equation was Y=0.0138X+0.0267,R²=0.9993.The average recovery rate of the added sample was 96.18%,with relative standard deviation (RSD) of 2.44%.The RSDs of stability,reproducibility,precision and recovery rate of the developed method were all satisfactory.Thus,this method can be applied to determine phlorotannins of S.horneri. The average content of phlorotannins in S.horneri was 17.36 mg/g (RSD=1.25%).

Key words: Sargassum horneri, phlorotannins, Folin-Ciocalteu reagent