Abstract:

Three different methods, ultrasonic-assisted acid extraction, ultrasonic-assisted alkali extraction and ultrasonicassisted
water extraction, were compared to extract polysaccharides from Haematococcus pluvialis with respect to yield
and physicochemical characteristics. The results showed that polysaccharide yield decreased in the following order: alkali
extraction (9.52%) > acid extraction (1.50%) > water extraction (1.29%). Scanning electron microscopy (SEM) demonstrated
that the cell wall of algae was most seriously damaged by ultrasonic-assisted alkali extraction, leading to the largest amount
dissolved polysaccharides. In addition, the polysaccharides extracted by ultrasonic-assisted acid extraction had the strongest
absorption peaks on Fourier transform infrared spectroscopy (FTIR) spectra, and all the three polysaccharides contained
pyranose monomers in their structures. The main hemiacetal hydroxyl was α configuration. The antioxidant analyses of
1,1-dipheny1-2-picrylhydrazyl (DPPH), hydroxyl radical scavenging activities and reducing power testes showed that
the polysaccharides extracted by these three methods all presented some natural antioxidant activities. Among them, the
polysaccharide extracted by ultrasonic-assisted alkali extraction showed the strongest antioxidant activity. It is concluded
that ultrasonic-assisted alkali extraction is an effective method for extracting polysaccharides from H. pluvialis.

Key words: Haematococcus pluviali polysaccharide, ultrasonic-assisted extraction, physicochemcial properties, antioxidant activity