Abstract:

The optimal enzymatic hydrolysis conditions for Porphyra haitanensis polysaccharide were determined as
40 ℃, 6.0 and 3 h for hydrolysis temperature, pH and hydrolysis time, respectively, by single factor and orthogonal
array design. The yield of reducing sugar was (1.42 ± 0.12) mg/mL under these optimized conditions. The saccharide
composition of the two hydrolysate fractions S1 and S2 was analyzed by liquid chromatography and electrospray ionization
mass spectrometry and their antioxidant activity was evaluated. The results revealed that S1 and S2 had similar composition
with galactose as the major component (accounting for 93.0% and 90.5%, respectively), and that both of them had good
antioxidant activity, especially for hydroxyl radical scavenging activity. In addition, the degradation products with even
degree of polymerization (DP) of 10–16 was more effective in scavenging superoxide anion and hydroxyl radicals than the
oligosaccharides with a DP of 4–6 suggesting the relevance of their antioxidant activity to DP, and considerable antioxidant
activity existed only in a specific range of DP.

Key words: polysaccharide from Porphyra haitanensis, orthogonal array design, composition analysis, degree of polymerization, antioxidant activity