Abstract: The trypsin-assisted extraction of polysaccharides from the muscle of cuttlefish (Sepia pharaonis) was optimized using one-factor-at-a-time method and response surface methodology. The in vitro antioxidant activity of the obtained polysaccharides was assessed and compared with that of those obtained by water extraction and alkali extraction. The optimum extraction conditions were determined as follows: hydrolysis temperature, 55 ℃; solid-to-water ratio, 1:40 (g/mL); hydrolysis time, 4 h; and trysin dosage, 2.5%. Under these conditions, the maximum polysaccharide yield of 4.15% was obtained, which was higher than those extracted with water and alkali. The antioxidant tests in vitro showed that the enzymatically extracted polysaccharide displayed higher antioxidant activity than the water- and alkali-extracted ones. At a concentration of 4 mg/mL, the percentage scavenging of hydroxyl radical by the polysaccharides extracted with water, alkali and trypsin were 50.15%, 55.14% and 89.47%, with median inhibition concentration (IC50) values of 4.51, 3.56 and 0.82 mg/mL, respectively; the percentage scavenging of DPPH radical were 28.89%, 31.48% and 40.80% with IC50 values of 16.66, 15.43 and 11.50 mg/mL, respectively; and the percentage scavenging of superoxide anion radical were 75.43%, 81.63% and 97.00% with IC50 values of 1.15, 0.69 and 0.29 mg/mL, respectively. The reducing capacity values of the three polysaccharides were 0.134, 0.156 and 0.193, respectively. Collectively, it was shown that the yield of enzymatically extracted polysaccharides was higher and the polysaccharides had higher antioxidant activity in vitro. The polysaccharides from the muscle of S. pharaonis have the potential to be a new non-hazardous and natural antioxidant.

Key words: Sepia pharaonis, polysaccharides, enzymatic extraction, response surface methodology, antioxidant activity