Preparation of Chlorella vulgaris polysaccharides and their antioxidant activity in vitro and in vivo.

In the present study, six different polysaccharides (RFPs, MAPs, UWPs, AEPs, HWPs and CEPs) were extracted from Chlorella vulgaris using repeated freeze-thawing, microwave-assisted-, ultrasonic wave-, alkali-, hot water-, and cellulase-based methods; and antioxidant property assays were performed both in vitro and in vivo. Radical-scavenging capacity (using DPPH, superoxide and hydroxyl radicals) and metal chelating ability were assessed in vitro; Caenorhabditis elegans was used to assess antioxidant effects in vivo. Based on the in vitro screening tests, UWPs exhibited high antioxidant capacity. The UWP yield was 17.1% ± 2.2%; the DPPH-, superoxide-, and hydroxyl radical-scavenging rates were 65.1% ± 2.4%, 61.2% ± 2.7%, and 56.2% ± 2.2%, respectively, and the metal chelating ability was 63.6% ± 2.5% at a concentration of 0.4 mg/mL. UWPs also exhibited high antioxidant activity in vivo. UWPs significantly increased the lifespan of C. elegans under oxidative stress induced by hydrogen peroxide compared with the control group, enhanced stress-resistance-related enzymes, including catalase and superoxide dismutase by 7.29% ± 1.8% and 24.41% ± 4.8%, respectively. The results of the present study indicate that the extraction methods of C. vulgaris polysaccharides were a key factor influencing antioxidant activity.