壳寡糖-有机酸盐的绿色制备、结构表征及其抗氧化活性研究OA

In this study,a green preparation strategy integrating dual-enzyme hydrolysis with organic acid modifi-cation was established to synthesize highly active chitooligosaccharide organic acid salts.The dual-enzyme hy-drolysis process was optimized using chitosanase and pectinase to determine the optimal reaction conditions.The optimal pectinase pretreatment conditions were a temperature of 55℃,a pH of 4.0,and a reaction time of 1 h.After adding chitosanase,the hydrolysis conditions were adjusted to 50℃and pH 5.0,with a pectinase-to-chitosanase activity ratio of 1:4.The total enzyme dosage of the two enzymes was maintained at an enzyme-to-substrate mass ratio of 1:25 relative to the chitin substrate.The total reaction time was 8 h,during which the reducing sugar con-centration in the enzymatic hydrolysate reached 284.87 mg/mL.The enzymatic reaction yielded chitooligosaccha-ride malate(COS-Mal)and chitooligosaccharide lactate(COS-Lac).Structural characterization by MS confirmed that the products were oligomer mixtures predominantly with a degree of polymerization(P.D.)of 2–3.FTIR and NMR analyses indicated that the organic acids were successfully incorporated into the chitooligosaccharides via ionic bonds,forming chitooligosaccharide organic acid salts.In vitro antioxidant evaluations revealed that both organic acid salts exhibited considerably higher activity than chitooligosaccharide hydrochloride(COS-HCl).The IC₅₀ values for DPPH radical scavenging were 1.10 mg/mL(COS-Mal),1.70 mg/mL(COS-Lac),and 2.44 mg/mL(COS-HCl).The corresponding IC₅₀ values for hydroxyl radical scavenging were 0.72 mg/mL,1.03 mg/mL,and>2.5 mg/mL,respectively,whereas those for superoxide anion radical scavenging were 0.32 mg/mL,1.54 mg/mL,and>2.5 mg/mL,respectively.Among these compounds,COS-Mal exhibited the strongest antioxidant activity.Therefore,introducing organic acid groups considerably enhances the antioxidant capacity of chitooligo-saccharide through synergistic effects.This study provides a feasible preparation pathway and theoretical founda-tion for the development of highly active marine oligosaccharides with different salt forms.