Abstract: Objective: To evaluate the antioxidant and antiproliferation activity of phlorotannins (PTs) from S. mcclurei. Method: S. mcclurei PTs were extracted by solvent extraction and separated by ultrafiltration. PTs content and total antioxidant capacity (TAC) were measured by Folin-Ciocalteu colorimetry and phosphomolybdenum method, respectively. Meanwhile, the scavenging activity against DHHP and superoxide anion radicals were determined and MTT was used to test the growth inhibitory effect of PTs on sw579 thyroid squamous cell carcinoma cells. Results: Four different PTs extracts including aqueous fraction retenate (AR) and filtrate (AF) and ethyl acetate fraction retenate (EAR) and filtrate (EAF) were obtained from the ultrafiltration of two different fractions (aqueous and ethyl acetate) of the crude methanol extract of S. mcclurei through a 10 kD MWCO membrane. The total phenol contents of AR, AF, EAR and EAF were 1.672, 0.096, 1.319 mg and 0.143 mg of gallic acid per gram of dry matter of S. mcclurei. AR had the strongest TAC at the same concentration (3 mg/L) and was equivalent to 2.315 mg/L of GA. All PTs extracts especially AR and EAR had free radical scavenging effects. Their growth inhibitory effects on sw579 thyroid squamous cell carcinoma cells at a low concentration of 4.4 mg/L increased with increasing treatment time and AF had the most potent antiproliferation activity and showed an inhibitory rate of 23.84% after 72 h treatment. Conclusion: S. mcclurei shows potent antioxidant and antiproliferation activities and thus has great potential for exploitation and utilization.

Key words: S. mcclurei, phlorotannins, antioxidant activity, antiproliferative activity