Ultrasound-mediated modification of biological properties of Sepia esculenta ink polysaccharide SIP4.

Ultrasonication is increasingly used as an eco-friendly method to depolymerize natural polysaccharides for improving physicochemical properties and bioactivities of the native macromolecules. However, a systematic evaluation is required to determine how degradation-induced alterations in polysaccharide molecular properties modulate their biological functions. To this end, this study focuses on SIP4, a bioactive sulfated glycosaminoglycan from Sepia esculenta ink, to clarify the physicochemical changes caused by ultrasonic depolymerization and evaluate their subsequent impact on biological activities. This work treated SIP4 using ultrasound at 50 °C, 450 W for 90 min. Physicochemical and biological properties of SIP4 and its degradation products were evaluated. Data indicated that ultrasonic treatment successfully depolymerized SIP4, the weight-average molecular weight (Mw) declined from 24.96 to 14.27 kDa, at the duration of 90 min. The depolymerization process fits a second-order kinetic model. The degradation did not modify the infrared spectral characteristics, but elevated the sulfate group content of the carbohydrate. Interestingly, depolymerized products showed procoagulant activity, which was opposite to SIP4 with anticoagulation. Additionally, ultrasound treatment modified some biological properties of SIP4, such as repressing the activation of α-glucosidase and tyrosinase, improving the bile salt binding capacity, and altering antioxidation demonstrated by increased scavenging activity for hydroxyl radical and decreased scavenging ability for DPPH and superoxide anion radicals. These data suggest that controlled ultrasonication is effective for modifying the biological properties of SIP4, which can effectively adapt SIP4 for specific practical uses, including hemostatic agents and functional foods for lowering blood lipid.