Purification, characterization and anti-tumor activities of polysaccharides from Ecklonia kurome obtained by three different extraction methods

To investigate and compare the effects of different extraction methods on the structure and anti-tumor activity of Ecklonia kurome polysaccharides (EP), three techniques, namely hot water extraction (HW), ultrasonic-assisted extraction (UA) and enzyme-assisted extraction (EA), were used to extract EP, and three crude EPs were purified by DEAE-cellulose and gel filtration chromatography. The significant antitumor active components in each method were screened by MTT assay and named as HW-EP5, UA-EP4 and EA-EP3, respectively. The molecular weight, FT-IR assay and NMR showed that HW-EP5, UA-EP4 and EA-EP3 were pyran polysaccharides with a molecular weight of 14,466, 15,922 and 16,947 Da, respectively. HW-EP5 contained the most monosaccharides and the highest content of sulfate and uronic acid. HW-EP5 had an even and smooth sheet-like appearance, while UA-EP4 and EA-EP3 exhibited irregular and rough fragments. All three polysaccharides can inhibit the migration of human breast cancer cells (MCF-7) and promote its apoptosis. All three polysaccharides promoted caspase activity during apoptosis. HW-EP5 and UA-EP4 up-regulated the expression of proapoptotic proteins Bax and p53, while EA-EP3 only up-regulated the expression of p53. These experimental results indicate that Ecklonia kurome polysaccharides, especially HW-EP5, have great potential as a natural medicine for the treatment of breast cancer.