Abstract: 【Objective】The effect of enzymatic hydrolysis by papain on antioxidant and tumor cell proliferation inhibiting activities of R-phycoerythrin from Porphyra yezoensis was investigated. 【Method】R-phycoerythrin of Porphyra yezoensis was extracted by ultrasonic cell wall breaking, and then purified by DEAE column chromatography. Orthogonal design was employed to obtain the optimal condition of enzymatic hydrolysis by determination of reducing powder A700 of their enzymatic hydrolysates. Subsequently, hydroxyl radical-scavenging ability and proliferation inhibiting activities of human sarcoma cancer cell U2O and liver cancer cell HepG-2 was compared as well. 【Result】 The optimal enzymatic hydrolysis of R-phycoerythrin was selected at an amount of papain of 25 000 U•g-1, pH 7.0, a temperature of 50℃ and at a hydrolysis time of 4 h. Under the optimal treatment, the reducing powder of the R-phycoerythrin was raised up to 0.573, which was 2.35 times higher than that of untreated group. Hydroxyl radical-scavenging ability was 51.03%, which was 3.22 times higher than that of untreated group. With the concentrations increasing, the growth inhibition of R-phycoerythrin and their enzymatic hydrolysates against human sarcoma cancer cell U2O and liver cancer cell HepG-2 increased. The inhibition IC50 values of R-phycoerythrin against human sarcoma cancer cell U2O was 2 431.32 μg•mL-1, which was decresed to 1 271.46 μg•mL-1 by enzymatic hydrolysates. The inhibition IC50 values of R-phycoerythrin against liver cancer cell HepG-2 was 1 593.61 μg•mL-1, which was decresed to 512.05 μg•mL-1 by enzymatic hydrolysates. 【Conclusion】The enzymatic hydrolysate of R-phycoerythrin by papain exhibited excellent antioxidant and antitumor activities, which proved that enzymatic hydrolysis could be an effective technology for further increasing the bioactivities of R-phycoerythrin.

Key words: Porphyra yezoensis, phycoerythrin, papain, enzymatic hydrolysates, antioxidant, antitumor