Separation of the polysaccharides in Caulerpa racemosa and their chemical composition and antitumor activity

Caulerpa racemosa was extracted with the combined procedure of neutral protease and boiling water to yield a water-soluble polysaccharide coded as CRP. The obtained C. racemosa polysaccharide (CRP) was fractionated with DEAE-52 cellulose, which led to two soluble polysaccharide fractions designated as CRPF1 and CRPF2. CRP, CRPF1, and CRPF2 were chemically determined and their antitumor activity was assayed. Results showed that they were all mixtures composed of sulfated polysaccharide with 3.9-7.9% uronic acid and protein, and had similar amino acid composition, but CRP was more than CRPF1 and CRPF2 in total sugar and uronic acid content, and less in sulfate group content. Two main sugars, glucose (Glu, 56.8%) and galactose (Gal, 31.8%), of CRP were enriched to CRPF2 (Glu, 89.1%) and CRPF1 (Gal, 99.2%) respectively; Bioassay indicated that all CRP had strong antitumor activity in both in vitro and in vivo, and its inhibition rate of K562 cells in vitro at the concentration of 6.0-10.0 mg mL⁻¹ and of H22 tumor transplanted in mice at a dose of 100 mg kg⁻¹ day were 59.5-83.8% (48 h) and 53.9% (14 days), respectively. Moreover, at a lower dose (0.05-0.2 mg mL⁻¹) and longer time (72 h), CRP exhibited stronger inhibition effect on K562 cells than CRPF1 and CRPF2.