Study on the preparation and biological activities of low molecular weight squid ink polysaccharide from Sepiella maindroni.

Sepiella maindroni ink polysaccharide (SIP) from the ink of cuttlefish Sepiella maindroni and its sulfated derivative (SIP-SII) have been demonstrated to possess diverse biological activities. But little is known about low molecular weight squid ink polysaccharides (LMWSIPs). In this study, LMWSIPs were prepared by acidolysis, and the fragments with molecular weight (M) distribution in the ranges of 7 kDa to 9 kDa, 5 kDa to 7 kDa and 3 kDa to 5 kDa were grouped and named as LMWSIP-1, LMWSIP-2 and LMWSIP-3, respectively. The structural features of LMWSIPs were elucidated, and their anti-tumor, antioxidant and immunomodulatory activities were also studied. The results showed that with the exception of LMWSIP-3, the main structures of LMWSIP-1 and LMWSIP-2 did not change compared with SIP. Though there were no significant differences in the antioxidant capacity between LMWSIPs and SIP, the anti-tumor and immunomodulatory activities of SIP were enhanced to a certain extent after degradation. It is particularly noteworthy that the activities of LMWSIP-2 in anti-proliferation, promoting apoptosis and inhibiting migration of tumor cells as well as promoting the proliferation of spleen lymphocytes were significantly higher than those of SIP and the other degradation products, which is promising in the anti-tumor pharmaceutical field.