Abstract:This study utilized Kandelia candel fruits from Zhoushan as the raw material to extract polysaccharide and employed response surface methodology to optimize the ultrasound-assisted extraction process. The polysaccharide was structurally characterized in terms of monosaccharide composition， molecular weight， and functional groups via high-performance liquid chromatography and Fourier transform infrared spectroscopy.The in vitro antioxidant activity of the extracted polysaccharide was evaluated through DPPH radical scavenging， ABTS+ radical scavenging， and Fe3+ reduction assays. The inhibitory effects of the polysaccharide on the proliferation of mouse mammary carcinoma 4T1 and EMT6 cells was assessed via the CCK-8 assay. The results indicated that the optimal extraction parameters for polysaccharide from K. candel fruits were ultrasonication temperature of 71 ℃， a liquid-to-solid ratio of 20∶1 （mL/g）， and ultrasonication time of 94 min. Under these conditions， the polysaccharide yield reached 20.809%， with the total sugar content of 71.771%. Structural characterization revealed that the polysaccharide comprised glucose， galacturonic acid， galactose， and arabinose （at a molecular ratio of 106.0∶3.4∶1.1∶1.0）， with a primary molecular weight of 295.249 kDa. It was identified as an acidic pyranose polysaccharide containing α，β-glycosidic bonds. Bioactivity studies demonstrated significant antioxidant and antitumor activities. The polysaccharide exhibited EC50 values of 0.028， 0.314， and 1.172 mg/mL for scavenging rates against DPPH radicals， ABTS+ radicals， and for the relative reducing power of Fe3+， respectively. Its IC50 values against 4T1 and EMT6 cells were 0.593 mg/mL and 0.681 mg/mL， respectively.