Abstract
The aim of the study was to extract Porphyra haitanensis polysaccharides (PHPs) using the water extraction and alcohol precipitation methods and explore their antioxidant activity and physicochemical properties. The single-factor and Box-Behnken response surface methodologies were used to optimize the extraction of polysaccharides from Porphyra haitanensis. Our results showed that the polysaccharide yield was as high as 20.48% with a raw material to water ratio of 0.04, and extraction time of 3 h at 80 °C. The extraction rate observed was similar to the actual extraction rate, thus proving the reliability of the optimization model. The extracted polysaccharides primarily consisted of galactose, glucose, and fucose in the molar ratio 76.2:2.1:1, respectively. The high performance gel permeation chromatography (HPGPC) results showed that the molecular weight of the PHPs obtained was 6.3 × 105 Da, and the sulfate content was 2.7 mg/mL. Fourier infrared spectroscopy was used to analyze the functional groups and structures of the polysaccharides. The effect of concentration, temperature, and pH on the apparent viscosity of the PHPs solution were studied using rheology experiments, which revealed that PHPs were a “non-Newtonian fluid” with shear-thinning behavior. The viscosity of the PHPs gradually increased with increasing sugar concentration, and decreased with increasing temperature, acidity, and alkalinity. Detection of the antioxidant activity of OH*, DPPH*, and ABTS* revealed that the scavenging activity of ABTS* was higher than that of OH* and DPPH* in the concentration range of 1–5 mg/mL. In the experiments of simulating gastric juice and alpha amylase in vitro, it was found that PHPs can better resist digestion of alpha amylase, and have better resistance than fructooligosaccharide (FOS), so PHPs have potential prebiotic activity. These findings demonstrate the potential of PHPs for use in the food and cosmetic industries.
Highlights
Porphyra, a seaweed belonging to the Division Rhodophyta and Family Bangiaacea, is widely distributed in the intertidal waters between the cold and subtropical zones [1]
Porphyra haitanensis polysaccharide (PHP) has attracted much attention owing to its composition, which endows it with antioxidant [6], antitumor [7], hypolipidemic [8], Mar
No significant difference was observed between the extraction rates at 80 ◦ C and 90 ◦ C, since the polysaccharide structure is destroyed at very high temperatures, leading to their degradation
Summary
A seaweed belonging to the Division Rhodophyta and Family Bangiaacea, is widely distributed in the intertidal waters between the cold and subtropical zones [1]. Porphyra haitanensis is one of the most economical seaweeds cultivated in China [2]; it is made up of proteins, sulfated polysaccharides, amino acids, and minerals. One of the primary active ingredients [3] in Porphyra, are made up of disaccharide units of alternating 3-linked β-d-galactosyl residues and 4-linked α-l-galactosyl residues, in addition to few 6-sulfate residues. Seaweed polysaccharides have gained importance owing to their antiviral, antioxidant, and antitumor activities [4,5]. Porphyra haitanensis polysaccharide (PHP) has attracted much attention owing to its composition, which endows it with antioxidant [6], antitumor [7], hypolipidemic [8], Mar. Drugs 2020, 18, 539; doi:10.3390/md18110539 www.mdpi.com/journal/marinedrugs
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